Industrial Materials Science and Engineering

8/13/2019 Industrial Materials Science and Engineering

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s30the plow and wheeled carts, and trader.s nr^chaî^_^ Muandarrvetarurgistsil;r# ;j:;.'H:._,1}ryiifTil,#::#i i""::H::T""rJ:iakingskills.whiremetarrurgveganitha

1.1ri1,,::ry, ffit #;l3Ll"*;l,1i;,!Ii,""rlno1"o""*uiFSi*=,ril:I:$1,,""rfi .x*i:*ffi+:1,'^',#i::*ir:{imes),he tiritvr*.turru.gv-ffi.,+{!.lj*: ;iT'::1":i:,*;:l lifurnacgail;";;edaroizationsegan ith h1fi;;;-i'i.i rvr,."*ii. ilon urougrrrn by "r',:i,,..'yirr"ji:.;",j;..tiesftT:::j::#:i:i:Ti:1,::f;::jfj c"pp*;i;: I.i"",*?;.i.,,#,llo.areductionn heempi;5ql:6in"uL',"**i[:*rr:]::'""'y1t;::.*,#"'J:l,,ffitft:,;',orked and copper smerting*u.-oY" copperwas castings i";t;-;;;;; ii"n^ rr," carbon contenr wasr;r';1,rri*i;''*lu#nk*;#i{.;I*;fi1'fi:;l{ilflasier han copoer..beca"..iir '_jrr'u, onty 232"C. ei n[,F'i:r;qptr"Tli'#+,1':{:;'" flH#ff.'"T'if{fi,;1""'#"?:,#,*:-,ti;;{ff##r;i3::ll :r:{{:iii4:t;'*:",,",HJ#';*,:.er' The mixing o_f i" ;d ^;;;.r-^rjut'"t of cop- high-carbon-."","i"irri iron) t-h.: ron*uluin urroylloy we call 6ronzeusheredn theI rproduceân produced"""ra J"'.ia..i::"::000",.*o reared;;;.,ii?,ri"if:lt**ijH:::l#i1j:i;'$t:;::'#*'td 'i::fl1#"ltiT:T5".*:"f"""::]iTi-'^-.ry'i-"J"av--",,i",iîi''*at",rsometheriqui;i::ff 1":"::t:tT'1:lffi33tr,f3;';:l:.1:i:.l:ffi*;:*{l1ffiinc to tin bronze,j^.rh9fraijir""iges ro form ui tastableunmetal.(say" ",1-iii-s;,";i" ?"i:T lj.l"*"-. temperatureo reducehe hardnessndealitv, hil ;;;-;i" r""rJ"ri", " ii" r? zn)' rn concomitanruliiii;".* ii *r,ut is now caredemper_llovs" hich .rlo.u. echnorogiJJf,*,*i""l"t 13fi"3:-ry?i;d""ir".u..uu.iourri'*-orr"anffi,'".13#'.',"il"11j:il,""li:j.fr:T[;':;;Sj;:,fff.#",Tli"ixiru**,::li*evelopment of an,1-ti,i*ti"r,;;"l'*ffiff rj,:i il?l["#]ng achievementsof modern irries]'ffi;airg i"ri, 6.2 MATERIALSFUNDAMENTALS:nergy, pacelight, air travel,"o._uJ"urion, ,yr_ v.. STRU-CTURE,riopnnTrEs, ANDIti:::"1 ilf:,"#,':"nic evicel;;;;" modern "_*ocnrsrNiriluoNsHrpsNodityt"m., l;:,';'::11"ir"',1*ff;;"sset,o,com- METAL.ANDALLoys^ It is believed hat eirly -; i";;"iron -or"^"iro r'i::irT:J#:::J""iTi:"f:Tfi:j,:"::l*i*.:t:,:t**iiT.T$"#ff;:i:l.i:::xlT tiqi;'::",fn',xllliTj #",'":r:n,ffi:#:"j;,l",ur",rmoreil.,,"r.rcheologicalspecimens.orten ho;;-'i-iin nicker, rise ,;",:1":j,T.:::._:i,l"tar atoms,whichgivesndnaturarron_nickerrroy,a*uruii",eNiz, ffi-:,ilflfir:,.:.:ffi::.; f*;"rutT, i::nd josephinite, Fe3Ni5) ;;;'"-;;# ,u.. ,nd tri."i. "onouctivity_; _;;;;i, becauseof the speciarfrF:,ri:$'.f'L.".:lHTJ.f;"ffl:1..."g'"r yl,l",lwrrichetai';;;are oundogetherondia nd hina ussesthaterrous;;H ""T f,T. *,il*i;,i{**n::r*::"["n#'"*


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IndustrialMaterialseither mimic the constituentsor produce completelydifferent properties. t is this diversity of propertiesand the aUifiiy to alter or manipulatepropertiesn acontinuous ; abrupt manner which .have

mademetals so tractable in commerce and industry forthousandsof years. n this section,we will illustratesome of the more important featuresof metalsandalloys-their structures,properties,processing, ndp".io*utt"e issues-by following a casehistory con-ceptbasedon chronologyof the agesof metals'Thatis, we will first emphasize nd a few exemplarycopperailoys and then illustrate similar metallurgicalandmaterials featuresusing steel and other examples'There rvill be some edundancyn these llustrations'especially n regard to the role of crystal structuresand defects in these structures' The emphasiswillinvolve physical and mechanicalmetallurgy whose

53 rthemesare variantson the interrelationshipsetweenstructure, properties, processing, and ultimately,performance. '6.2.1 The PhysicalandMechanicalMetallurgyof CoPPer nrlCoPPerAlloYsFollowing he extractionof metals,suchascopperandtheir refining to produce useful forms for industrialutilization, metallurgybecomesan adaptiveprocessinvolving physical,mechanical,and chemical ssues'suchas tectioptatingand corrosion, or example'To illustrate a wide range of these metallurgicalprocessesand related fundamental issues,we willtegin rvith the example n Fig' la which showstiny(7ipm diameter)copperwires that provide accesso

:

Figure I (a) Smallsectionof integratedcircuit showing75pm diametercopper'bondedconnectorwires' (b) Schematicepre-sentation or mechanicaldrawingof these ineconnectorwires hrough a traiae.teadie.The drawing operationshown epresentsinhomogeneous eformationwhich is contrastedwith homogeneous eformation of a simplestructural lattice'


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532

;ffJ"r:|'Li1 anelectronicircuit.Suchmicrochipsfr"fA ui",ifui# a great ariety f devicesr;;;;l:rh..";;;;;,f j:"ff:,yji"jlt '.il;;";ri.:drarvn n a seii.* .,r-,,,i_'l_^lqrrdule wtres must bebeginwith tn. o."tr.lf^.*ire-drawingoperationswhichi"u'irviii il:;f::,"-tton oree'ee%oopp..od nom-mirr."ri'ffi#:l Ji#,::';l"t"t:lu'p*rq"'",iacesses,lustrated."r,.rnuii"i1;;;; senes f pro_wiresdrawni.ough.ai"-'i".r"o;:;l,?ii#:,T:;T#T::1fli".1"":'.:. "ro'*utionlrdispracementthisdeforma,ronuonr,, in the nitial rod. To f";il;;;;peraturesr"or,"l1.l: l*ytlg operation,l;t;;:a*r,r,* tr". :.';l'Yt* andthisdifferentiater-t oil'suchoperati"r, #,,'l-tlving operations'The ,.uiinI:"1d;;ii,iiliilllii[ l.f#,",,"iitr-iff|"""# #*::"J.* irm.*"* ","lpreaaingorawarmburter ,flo*.l, :::l"t on.breakfasttoasi trrefi;:;lil:l *:iii!#:i:ffiH:i:r;ruptedduringo.urt3ut" if the flow becomesntei-and thewirecould lll-F'S lb)' cracksmav form;r*rii:::ff:_::.t"t5"i"::i;l:^.,::Hitionsin;;"_"ti,""ir.".,1ffi';iTi:fit1l::rJfrausea crackedwire to break.. The flow of coppr,1yl' r; rc r'b:'tdT'1ifffi".Tilf:l,"ltftT;il,,H il.iLffj:naing iiiJffiil orcopper,:?T:,.",,,",41FiK:!":?l*,T:iT"l:Kecopper,beginwith the atomic;il;;., atthough:ff :ff ,:'il:'J;"",',sris ;; -"iHd"'J.u,iwiestructuiet.r."","r"i,9lment of theatomsn acrystalis alteredl.ffil;lunrrs composedf atoms, hichunltswhichnlurt ..noJ.l,atoms r atomic structural)

Mueachshellhave otaltional to z-ni;;;*" energieswhich are deallypropo(rz: l) areclosest;Yly'the electronsn tt. r.Ij

6.2.1.1 ElectronicStructure f Atoms,UnitCells,and Crystals;1.'J:ilH.1ff,,:':::::^'n:,uil,et s ookt heoruu.iou,ii-il:Tll91a1ns erictinghe ormation,T."Je"F,c.. .":,TJ;:: l"?::::lx".,,::zedby 29etectrons("1"_1"',i"r;;,;i; a specificfl:'::i:ffiffil11'.(:lll':1.t:Joii,jlea,z, ,::p,,ntl; fi:i"":i,^1,:i,jfU"f;,:;,ff?,1lubshellshave he sameenergy, f,1. uii-"lectronsin

Figure2 Schematicel..;::",t:fjJt'.:, 1 i,;".ffil'#il'fl:'::ti:*l;.'";;;;";;:ffifff f ",l,,,li,r,ii::$.atronshaded)and 11;i1n".5.a;";;rffisement. (c)rystal unir ceilconventionsshowing ,t0;.;;;". (shaded)lilJ,.:i: ff' lil'i;, . o i'pl.'pi""u#J,t.ipotnroughcopperwire n ,{! lttttt-oimensionalsection ieriup of unit ; j l , . """ '' r ' I$' l8 showing rystal rainsmade


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533ue(o.o5A)Industrial MaterialsH(OJ6A)7=i 2Ne

o10

A.1 8Kro3 6Xeo54Rno6

FoI

CIo1 7

s r Y z rN b N / o k R u & ro N K N K K B 6N N S N N N N N N s o3B

N 8t AAI Si P Ss ? P . 3Co Sc l i V (N N N N K K K K N ' S ' K K E 20 21

B Co o5 6(r.isA)eN4LiN3NoN1 1KN1 9RloN

Se BnO o

Bi(1.824)N83PllN

Kr(1.64)1 2

a Eo Lq Hf To W ReOs Ir RAu Hg 11N N S I S N N N N N N N N NY E6 - Vr'r-r,(LonthonideSeries)(2.74)ATOMTC UMBER. ELEMENT YMBOL.ELECTRONICTRUCTUBEEQUENCE

67 Ho68 Et69 Tm70 Yb71 Lu72 Hf73. To7 4 W75 Re76 Os7 7 k78 Pt79 AuBo Hs81 Tl82 Pb83 Bi8 l P o85 Al86 Rn87 Fr88 Ro89 Ac90 lh9l PoE 2 U93 Np94 Pu95 Am96 Cm97 Bk93 cf99 Es

34 se35 Br36 Kt37 Rb38 Sr3 9 Y@ 7 r41 Nba2 Mo43 Tcl H R u45 Rh6 P d47 Ag49 cd49 lh50 Sn51 sbs2 Te53 154 Xe55 Cs56 Boq 7 t ^58 Ce59 P(@ N d6l Pm62 Srn63 Euu G d65 Ib6 fJy

't s13Hz H e3 U4 B e5 B6 C7 NO O. 9 Fto Net t Not2 Mgt3 Al1 4 sr s pt 6 s1 7 c lt 8 Nt 9 K? o c o21 Sc22 Ii2 3 v24 Cr2s Mn26 Fe27 Co2g Ni? p - c u30 zn3t Go32 Ge:|:! As

Figure3 partial periodicsystemof the elements howing he metals shaded).The elementsare-rankedsequentiallyby atomicnumber Z (or thenumberof "l..trons; whichare llustraied n an electronicstructurenotation shownbelow for Z : I (hydro-egn) o 7 - gg(einsteinium). elative izes f theatomsof these lements re ncluded.Atomic radii areshown n parenthese(A).

24p


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s34possesscharacteristic,valences and ionic or atomicrzes. onsequenty, ttrisctrari-uJiolr,"i.u"or,.k guideo- redictingspecificombination,"i, "*"Urtitutionsol, elements n a stru,specinchd ;"";;""jffit[x fiLl"";:::,'J:j;;"^loa3l,r, rvhenatomscombine;-;.; bound oorm solids, heyalso irst create-u;r-;; unit cellshat have specific eeaescriueJii;;;ffff:T!'".,,::f;"rfl*fi ;:",*:::$'lli:Tffi"'."#""d8'u;;;;;;,'""",1'in",.r""nun '' ii"'" ;;.";:'J::j ?ljtemso crvstal tructuralunlquesystemswhich arecom_

Muposedof a total of 14Bravais atticesshown n Fig. 4heseunit ceilshaveatomicdi_";;;;enoted a, b:ffi :i'#:'::Tl:":lticarrvirr'ris, *o ti,.,.,,!,o,_"riilffi ff, 'J::'tr.::;::rurutIil;i " 'il Tff ll:..T,""4;ii' Jn, fercrystarnits,uiiilff:Jlff il:'# ;iff,,h?jronic configurationkinaren'er'Jffi:i# fif,T':1fi:ili"::*tomic unit. Conseouently.,.rn.rut, ;;;;, copperilver,gold, palladium,unJ iriAiu,' nJr_u'y form a

a * f * ya * b * c d - y + Bf =so' -Base-centered Bodycentered

Eody-centeredtetragonal Trigonal

a * b * c

a = b = Cd = f = y * 9 0 '

Face entered

a - b * ca = f = y = 9 0 . a = b * cd . =p = 9 0 . , y = 1 2 9 .Face-centeredcubic

a * b * iSimple etragonalHexagonal

Simplecubic Eody-centeredcubic

a - b = cd . - F - ? = 9 0 .Figure4 Atomic unit cells haracterizingcrystalsystemsomposedof a totarof l4 Bravais atticesshown.


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Industrial aterialsface-centeredubic (FCC) unit cell,while metalssuchas ron, tantalum, and tungsten, or example, vill becharacterizedby unit cells having a body-centeredcubic(BCC) lattice(or crystal)structure'When one examineshe atomicarrangementsn theunit cells as shown for the shadedplanes n Fig' 2'theseplanes also exhibituniquespatialarrangementsof the atoms, and are designated y a specificndexnotation called the Milter or Miller-Bravals (in thespecialcaseof hexagonalcells) ndex.notation'Thisnotution is simply derivedas the reciprocalsof theinterceptsof eaih plane with the corresponding xes(r, y, L in Fig. 2), the reduction o a leastcommondentminator, and theeliminationof the denominator;e.g. llp, l lq, llr wherep, q' r representnterceptsalong x, t, z respectivelyeferencedo the unit cell'ConJeq,tentlyoi the plane denoted 1 I l) in Fig' 2'p : l ,q : t , , - l , and or thep lane enoted001) ''O: *, e: oo, : l. Correspondingly,f we consideri t t " p tu t t . o rmed vhenp: l ,q - l , 1 -nd : l f2 ' theplane would be designated1 12) while a plane withp: l, Q: l, and :2 (extending -ne nit outsideheunit ceit) rvould be designated (221) planewhich'rvhile llustrated n a geometrical onstructionoutsidetheunit cell,could ust aseasilybe shown n a parallelconstruction'withinheunit cellwith p = l/2,4 = l/2'andr : 1.Thisnotationcanoftenbe a little confusing'especiallywhen the oppositeor a parallel plane isdenoted.For example, he opposite ace of the FCCcell for copper n Fig' 2 [planeopposite 001) shownshadedl oincideswith thezeroaxis z) andmust here-fore be referencedo a unit cell in the oppositedirec-t ion ,namely : ? ,q :6 ,and 11 -1 ' * t des igna tesucha ptan! OO ) (ttt. negativendex s.denoted itha bar aLove or conveniencend convention)'You caneasily show from your analyticalgeometry trainingthat for the cubic unit cells'directionsperpendicularto specific rystalplanes ave dentical ndices'That is 'a direction1i r f1 is perpendicular o the plane 1I l)'Note that iit."iioni are denotedwith brackets'Weshould also note that planes of a form, for example

all the faces(or faceplanes) n the copperunit.cell

(in Fig. 2) can be designated s {001} and directionsrvhich are perpendicular o theseplanes or faces)as( 0 0 1 ) .We have taken the time hereto brieflydiscusshenotations for crystal planesand directionsbecausethesearevery mportantnotations' t shouldbe appar-ent, for example, hat looking at the atomicarrange-nents for (0Ol) and(111) n Fig'2 is tantamountoviewing n the corresponding001] and [l1l] direc-tions. maginethat you arehalf the sizeof thecopper

535atom and walking n one or the other of thesedirec-tions in a coppercrystal. maginehow much tighteryou would fit- in the [l I l] direction han the [001]direction.Thesedirectionaland geometricaleaturesare correspondinglymportant for many physicalandmechanical top"tiitt of metals, ncludingcopper oranalogous .utott.. Electricalconductivity,which canbe visualizedn a verysimpleway by followinga singleelectron raversinga finite length along somespecificcrystaldirection ike (00 1) s a case n point whichwewill describe little later.6.2.1.2 Polycrystals, rystalDefects, nd.MetalDeiormationPhenomena: Introductionto Structure-Property RelationshipsNow let us return to Fig. 2 and Fig' l'

We are nowready o examinehe "test strip" in Fig' I which llus-trates a small linear segmentalong the tiny copperwire. A pieceof this strip can be imagined n Fig' 2to representirsta continuous rrangementf unit cellslike a repeatingarrangement f crystal-blocks'Youshouldnote ttrat n the contextof our originaldiscus-sionand llustration n Fig. 1 of thewire drawingpro-cess,hat like individualatoms, he FCC unit cell for"opp.t is alsonot distortedor displaced y the defor-*utio.t. That is,.the unit cell dimension or copper(a: b: c : 3.6A) is not altered'What is altered' sthe onger-range eriodicities f these ells hrough hecreatioi of aefeits which are characteristicof theseatomic alterations.Such alterationscan also includethe creationof crystaldomains,which are llustratedin Fig. 2. Suchdomains,calledcrystalgrains'can bevisual-izeds rregularpolyhedra n threedimensions'and solidmetalsare normally composed f space-fill-ing collections f suchpolyhedrawhichproducepoly-"rirruttin. solidsn "onl.uit to single-crystallineolids'Tie interfacer or common boundaries where thesegrainsor individualcrystalpolyhedrameetalso epre-Jent defects n the context of a perfect' long-range(continuous) rystalstructure' t is easy o demonstratein fact how grain boundariesas defectscan have animportant influenceon both the strengthand the elec-trical conductivityof the copperwires n Fig' l'Figure 5 providesa graphical llustrationof a testsection hrough a polycryitallinecopperwire and asingle-crystalection oi *it" (whichcontainsno grainboundaries). he grain sizeor average raindiameteris shown n this sectionas D in referenceo the thick-nessview in Fig. 2e.Note that the grain boundariesconstitutea discontinuity n a particularcrystaldirec-tion or orientation.f a wire sampleasshown n Fig' I


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s36_Wte,m,t)-w.

srmpeelectrffifrn-dft[,9]t =chcej mv ; 1(1_k;D).r=g roi-i ioriaq=1/P ; p=pes11=Ar.a. , S=V/cm

Mu,t;:"1""d:3ff: '.i.:r:Ib::smuchmoreuctitehregimefi;ffi;iJ::" No'"alsohat r,.prusmalt elasiic-;;;;n.r" curves_thereis only ; ;;;;::r;l; i #:i:H:f".."ftT;::*:'?:fr::#;#;; :i: ^'"' *irru[o n.,0'"*o,u,tar irejali;;::::,iy:il.:lll,ffi**:i;l:rrated n Fig. 5.

"d:*:;,f,,t:3;:," *TP'" rererencequaren rhnecessarilyhave nv ,lt-ltq 4' Thissection o., nothecrystat;;il?:'tple geometricalrelationshi;';related,"'rilicd".?Lt"v,. ^.nictedhichru,u."imustbe noi.a'fi,":'t':.':]l for copper'uo*tut.,liunit cell t ""; i;;;lf :'Yt-"gplasticderormation,ihewav hisd;;;;i:

drlsjorted'nd he o"rv ."ntifr.groupsof unit""11,htot a co-ordinatedslipbetweeis, the ..;,;;;;;;';r;;::: t" ,the ight n Fig.6. rhatLgatronA/) experien"iAUy t "

e=Al / la=Ee (Fboke,s Lsw)n /

n / n/ u 1 g8,ffi#R,"",(1t.tm;

Figure a""Ourn::1:l^featureldistinguishingpolycrystal_rne a) angsingte.:ly,r,"l n.tut ."itoi, ii, uno heir ote:l.T|ffi"l1H,1i,T::l11::,(,:;;ti;i&|'aerectricarlcon_,rt. "J'J^"ra'rf'j1:lttferties' Noten(c) hatd;;i;area. his .uotu,lll'-1t*s" or reducestscross-sectionalstrain (e) br;;;;"t:,-t (e.) is contrastedwith th. ;;;;;h.T,1{,ir',nJ",,r,,i"'i,"";!,:;:r;,''/'ot:}:,'::i;;i:alue). 4u : a - do (a negativewere pulled in(stress-i"*"l"r"rtension and the st,1rher ; ""Tffi1'l,1T?fl,:1i,i:.,,*,,;#i(:,!tlffi iill Tr"",1 ii,",u ' i ".,,o nnFig .curves vhererr" .r'1-ltllar' elastic ortionof theseFtriiill"l*,'Jt*'1,i":ii;F'#:lJiln,',:"xT;j:: "*,*,"i.t,r,ilft,ilfi"r#Til,:,""xx;::..n?t:r. nengineeringietd "iri J, urit rvhich oint he1.tj i, "; l;;;;; i"'rl,,n,n, rur_,cary,andthe..r"*ri:lf":'ii':-:'{:!::';i:;"121recoverable.Th" -r3,11ion becomes lasticand non-: 1Y:'s.cal ;;J. ,lfl ":::,?,:":::j,,l,jft';whlteop denotes he-stress t fru"iur.. tor, ttut tt,.otycrystallinewire Ithani,e,"r1;;;:,iiTi :."1#:1";T:i"$jjlso hat thesingle rysralwireh;;';;; trger strain

ffi_.__\=-,Ff++ ,'lf* ,:i""l./* /______J sneor

=O.2o/o

A

$iu%"--,T:-J:?:',,::Tfl1"":H?q:*'1:'1)o d)'ustrateherea-: :l?di;'d;"i#1"il:lf:1':',1T:'?,:,':".erect varying from edpu.uu"un.y i; Affi;;": toscrewsshownn (e). r)showssttesand an interstitialrj:l-:t'it::i:nal impurities n atomic;: ff1,*g #d;F:#I,.t,ij,;,;,fl :#: ,i


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531IndustrialMaterialsplasticalrydeformingwire is the combinedslip of co- dislocation merging n thesurface reates

spi'alstepoperatingsegments. .^ii*rn, out, slip in FCC crys- o' ";";;;;' A;"; addedsvstematically

o this steptals occursexclusivelyalong {1 1 } planesat room canallow the face o grow bv a spiral

growthmechan-temperature. his is b"ca,r.elas'lustrateJin-nig-0, ir*..einuriv,note

that.the ttal iislocation n Fig' 6ethese re he close-packedlanesrefer.atsoo'i,sioj .T !.;;;tea ty imagining he solidsectiono consistand the atoms require only a modest ..for""l ,l!or".a or u ui*t oi l.ri-o *ii"tr is sliced

by a knife from facein the slip plane to ,r*.r# ihe atoms na .q,ririuriu* ,o ru." una the (l 00) face displaced

by a unit amountpositions.rni, p.oJerr'*rr- o""u, withoui br"ati'g -r/t/).-it e cnuru"t.. of the lini creating

a demarcationbondsbetweenu,o*r.o, without stretchin!"b"J;. il io. tti, cut and displacements

the dislocation inefact, unlessat least'ir"fi' ,t " unit transla,i-o' fo, ,*o *f,o," "t'u*"itt "ttuttgtt from edge

o screw(cr 90"reference 1 I l) ptur,., is achieved, h.';i;;;, ;"r to o;j in a continuouswav' At

the midpoint of thisrelax back to their original positions--rlastic deforma- q.,rurr", circle the chara"t"r is

said to be mixed

iiT":iiigtT*.J:mn::::Uiili$ill'?j i_:fi'nowdenned,p'u''oundariesr rvs5, and 6. For .i.rrprit'iiv, *: -huy:. ,rt'ir.i -it. ici ir*.i"."ii" a potycrystall-inemetal asdefects actually(001) plane u, u ,#r.nce ,.block,,", " rg.""jrr"*" :l.tj;;ilu'L' u" oft"n referred o asplanardefectsbut slip in FCC d";;;;"".r, i., the {001} pranes s ir ;;.vri;liitt. 1ot polvcrvstalline)solid' as rvell asshown,but rather in the {r l r} planer..lir'r"qrir., airnroiio" lt", )ryritt,-it ls probably instructive osomecroseexaminationof the geometries iJ "ivr,ur 'rustrate a few other common crystal defectsasstructure (unit cell) norations. sh";;T n11 9t-i ytl:ttt the simpleunit cell sche-Figure 6a_d 'rusir-a"tesl ru*r., simple scheme or matic, Fig. 6f showsa missiig atom in a crystal attice'slip to account fon^il; irrorrgutiorrl rr-u "rv*ul Suchmissingatomsarecalledvacancies'n contrast odeformed n tension.And while we do not a'ow for g;-;;;;;ut1 !_1ul:r,,defectsand dislocation inea unit cell d.istortion in response o " .,r"oJi"r'*o lefects, a vacancy is- ideally a point defect' otherrotation about the iension ine (dotted ' r,ig. 6-a nd po;;;d; "un b. illustratedby substiturionarmptt-b), or a unig shear,combinationsor.t"nrion ind shear ,;n , *tri"tr sit on the lattice (atom) sites'or-fnterstitialover millions of iattice or unit cen dimensionscan oro*, ini"ncan be the sameattice atomsdisplacedorationalize he displacementsecessaryo accommo- nonruttice ites,or other mpurity atomswhichoccupydate huge prastic

"d;;;;i;";, such as thosewhich "";i;;i;; .it". ig' eq)' ln Fig' 6h a seriesof vacan-may characterizea wire drawing op"'"'i; atprct"a tt:;;; u uutu"t'v disc which'

if large enough'willschematicallyn Fig lb. ailow he lattice o essentially

ollapse pon this discIf the unit aispii"em"r,ts imposedon the lattice by Til ";;;; a loop whoseperimete.r

s a dislocation:aslipare ot ransui;iii."gt ft. tuui.",1*-* l!.;r aiirtii"n/oop. Tiis pointiupan nterestins

roperdeformation ccumulaten the atticeasdefectshar- "i" ai'i""ution ine' t "u" "n-d n

tself as n formingacterizedbyanextrahalfplaner:l"Tlsuchdisplace- ";;;;,;; a

*stt'fac""'suchas an internal raimentuniton thesripplaneFig.6d). n.* riip-rir","a uo"niuiv, or a freesurfac", r on

another islocatiodefects re called isrocations,unarr."rrnii-iirpr"*- rine.Disiocationsever implyend

n a crystal'mentshichr,u'u'I"'i"hemre auedBurgers ;i;4'f j*""t;:1,*tT6;'ii-":'::t"y{',vector, and denoted b'As shownn thesolidsection iewof Fig' 6e'a total r""gi ""*Ut: "lii:i1til Suchdefectsanbe ormedislocationn a metalcrystal or any ,t.? "rvrt'ir" byleutron damagen a nucleareactorvhere tommaterial)canbecharacterizeasedge , ,r,,i'A dis- ;i"H;"J-;d;;;

vacancies hich ca'' difuseolocations in effecta rinedefecti' u. rv.tut,and its -Gt; through he- attice o createan aggregcharacter(edge,"r"*, or a mixture)s determinedy fiffi':;^;rfi. ittir li"ress

is facilitated y higthe angle a) betweents Burgers ector b) and the ,",,'p.ru,ur""a'dwhenh'eii',t" r

created s-anntersdislocationinevector(f). Notg ri r]s. o" lnut to' " ;i"fiil;flI it tl"

-"u"ttut reaction' t can alspureedgedi.tJ;;; ii',rr. {001} fice the Burgers ;iltTt aiT"t::t to it'o" void

aggregateso forvector,b. is perpendicularo the disrocationine ;;;:;ii";;^phic

"bubbles."This process ausesh(n : 90,), rvhile or the emergen,.i"* dislocation "rigi"^r

"meiatin ttre-eactor nvironment-towellline o the eft t is parallela :0"). In theFCCstruc- ;::"#ffi; itt.r. u"uures'

nd hisnucleare.acture,as , ,,ot.dltie slippianes{r r rt and hedirec- ;lG 6t more han6o/o) an

pose nique ngrntionof theBurgeis ectors (1 0).Note hat hescrew i"g ;.;ils in reactor esign

ndconstructton'


10/38

538Figure 7 illustrater:l,::a"b.";;;;i;i,.:,1{":..::h"jilli1l,.ij.i:Ll?ote especialtythe dislocations"_;;;;;, from therarn boundaryin Fig..7b *hi";--"an*l;rreconciledwrth dislocationsformid u, ,r," .*"i.rr"l, " surface

Mstepn Fig.6d.This sa :lTpl" examptef thepropi'n i;ffi ::.:ljil:',*t .r,unui'"iil"rdisbarrier.i rr-,r,# l"!-,Y ^slinst.theruin ounJa dbari rs-".L'Hlff ;: j|'ff:i il.r:ffiil{O.5lrrn

1 l j\ .tr,,!;oi , . r, :-, , \,* i ' - , i itu

L

Figure 7 Examples of crvstal ;crenr. :_ ^ -***i*'ffiH'$'':":tffitrfil#fitli:rn'ffii'j.iii';.xs[:riilli:ilrduringr,. "lioiA""l,i"',j";,S::11il"'*:t*.opperod, omer*i*o


11/38

Industrial aterialsgrain boundariesand grainsof varying size,D, on themechanical roPerties f metals.If we now returnto Fig. 5, but continue o hold Fig'6 n reference,he differencesn thestress-strain urvesfor single-crystaland polycrystalline opper shouldbecome-apparent.uring tensile training,slip s acti-vated at -some requisitestress.Processes imilar tothose llustrated n Fig. 6d occur' and many disloca-tionsarecreatedduringstrainingwhich arenot trans-lated hroughthecrystalbut begin o interactwith oneanother,creatingobstacleso slip and eventual hin-ningor neckingof thecrystal,and fracture'For poly-"ryJtullin. "op!"., slip is quickly blockedby the grainboundaries hictt rapidly producea host of disloca-tions which createadditionalbarriers o slip' causingnecking,and failure.As the grain size,D, is reduced'the stressnecessaryo achievedeformation isesandthe elongation will often correspondinglydecrease'That is, as the strength UTS) increases,he ductilitydecreases,nd the ability to form or draw copper itsmalteabitity) s also reduced.We miint argue hat otherdetects uchasvacancies'interstitials, nd substitutional lements ill also nflu-ence he mechanicalstress-strain)roperties f metalsby creatingbarriers o themotion (slip)of dislocations'In fact it is the variance o slip or dislocationmotioncreatedby substitutionalelementswhich accountsnpart for the variations n a metal'sbehavior suchasstrength,ductility, and malleability)when t is alloyed(or riixecl) with anothermetal' We will discusshesefeaturesn more detail ater.Now let us finally consider lectrical onductivitynthe depictionsof Fig. 5' Consider hat Ic denotes*"un i'r". path (average) or all the conductionelec-trons, tc, utti"ttmoveat somemeanvelocity'6' If n" e(the charge),m (themass),and d are-u.nchanged'nlyl" will sig-nificantlynfluenceconductivity' For a singleciystal, Ihi, tt "utt free path would dependupon thecrystal structure and the directionof conductionofthe crystal orientationof the wire if it werea singlecrystai.That is, the kinds of atomsand their organiza'tion relative to electronsmoving as masspoints orparticleswould cause ollisions reating mpedanceoilectron flow. However'assoonascrystaldefects ereadded to the wire structure,the mean freepath (pro-pensity or electron ollisions)wouldbe altered'nvari-aUty strortened; thereby reducing the conductivity'Obviously some defectswould have more dramaticinfluences han others. Grain boundarieswould beexpected o have a major effect,but includingothercrystal defects n a polycrystallinemetal would com-pound the reductionof conductivity'And whileredu-

539cing the grain sizemight strengthena wire, it mightalsocorrespondinglyeduce he conductivity'Temperature vould also have a very importanteffecton metal conductivitybecause ncreasing em-peraturewould createsignificantvibrationsof latticeuto*r. In fact at very high temperatureshe effectscould become o arge hat atomswould be dislodgedfrom theirnormal atticesites, reatinga vacancy ponleaving he siteandan interstitialupon squeezingntoa nonlatticesite.Not only would the vibrating atticeatomsprovide mpedanceo electron low by creatingadditionalcollisions, ut the "defects" createdwouldhave a similar effect. Consequently, resistivity(p:l/o") is usually inearly related to temperaturein metals, decreasingwith decreasing emperature'Crystal defectswill alter the slope or the shapeofthis trend. When a metalbecomes superconductor'the resistivity abruptly drops to zero' When thisoccurs, electronsno longer behave as singlemasspoints colliding with the lattice, and defects' atherihan impeding he process' ontribute by promotingincreased urrent densitY, I.Utilizing a fewsimpleschematics,we haveexaminedsomefund-amentalssueswhich have illustrated someequally simple mechanismso explain physicalandinechanicalpropertiesof metals like copper' Butthesellustrations nlybegin o providea metallurgicalbasis or suchbehaviorunder specific onditions'Forexample, he drawingof very thin copperwires rom

barstockorcastrodinvolvesmorethansimpletensdeformation.On forcing he metal throughthe die inFig. lb, the stresses re not simple uniaxial (alongthJ wire 'direction), but involve a more complexstresssystemwhich simultaneouslyeduceshe wirecross-section'Consequently, nderstandingpracticalmetal-forming operations such as wire drawinginvolves far more than a simple tensile test'Correspondingly,ensile ata,suchas hat reproducedin Fig. 8 for a numberof metalsand alloys'must becarefilly evaluatedand cautiously applied in anyparticular engineering esignor-manufacturingpro-cess.This is becausemany practical engineering on-siderationswill involvemultiaxial stressor strain' atelevated emperatures,nd at strain rateswhich arefar different rom the conditionsused n developingthe diagramsshown n Fig' 8 where. ensilesamplewere strainedat a rate of l0-3s-l' Also' the micro-structureconditionsarenot known or unrecordedorthe particular materials,and the effectsof simpledefectssuchas grain boundaries and grain size'D)are therefor. unkno*n. Furthermore' as shown inFig. 9 the productionof dislocationsand their ability


12/38

540

['|T' i -|:fi f"Hl::",]"e te.nsiletress-straindiagrams(_ 20"C). .rri"r..rill]:.""0 alloys t room emperature(Afterdata l'd;. l:;ructuresare noted in parentheses.to slip on specific rts different", ain';ljjitl-1i1": andcrvstal irectionsXf::tlii;li#',"#'Xt.'J,"fi1.?TJiTiallovsof ;;;;':oart lor differencesin metalsaninci-i6z', ilTJ-*1li"l:'y (suchs!u' Ni':l,u:t:,:,,il;';;:a3ii:"giti:il,:l.,ffl?1]il il't ?,1?i:;.,'j".T1i" ",n,ii*o",ripry,gramand n theutilizifl sha^nef a stress-strainaia-commerciar", il;il:ff;:I;"r. and uoys;;;

6.2.1.3 MetalworkingandMicrostructureTo examinehesessuesn moredepth, et us considerhe major metalworkin""";.""j:1]ll"lt ' .ingni'h;il;,";tr,%H';::#fi:ffi .""j5

Murrsheet-formingoperations_dieforming,deepdrawins.nd punching.Theseu." iilurir"t.i.j".riro,. sketche_eprod ced n Fis., 0.N,";;i;l":; ;;;:,.r,., invor esnty uniaxialr,.i1;2!.1;'ffi:ffi manyuchperationsarenot performedat room temperatureor'1,!::?#:: H:l:' F". ; ;;;;ffi; rvie-daw-ro\";-t;;;;xid,n,i;:.;",i.f"Tn Fig.8 rvhichsnominallyonly'ft:i l* ._-" ru",o.,"r:3"il:;: l";::'t "" ir""'r""i"'.,i u oo affl:TT:"","'#.",:J:',:iTi.:lf:metalworkin*iunauf,llt yh'"th deallyllustrateher0' In fi;;i";;1T:"::" ror each rocessn Fig.Fig. ll ut ;*"r;;etne stressor strain components,asanotario""r:;;;"'"JJ';,i:::;:ili;H:,Tcrystals.n fact,essentialtyil^il;i,rilperries arerrectionalandcan1"_*"1.0 ur.,."rolr]Figurellso showsother deformation."a.r"r i i.h, whileot necessarilycharact"rirtic oi ,iliut" iro..rring,epresentsomepractical performar;;r".rs twistingr torsion,fatigue due to cyclicstre{ u"ni"u.ry to*,umulatiyestraining,or creep.

=UIUIoc)L0

12stroin (%)

& #:onstroied un7orstroineo|f;.!u,j!'*o'u"tnlr " &oT,H:ln15o.''nnWwf'(oo1) (OOOI)

@%tFigure9 Slip systemsn metalcrystals. Figure 0 principal metal forming processesnvolvingvar_ousstates fstrain or stresso in cubenotations).


13/38

IndustrialMaterials

-.{I' r . # = # '

c*(tension)UNIAXIALn}| ltsl lax(compression)

Ior:oyAAXIAL+- ' l l . -t t

lo :f(e,i,Z)11 @iaxial) (2)

- - sheon -+| . | / ..^o-./ .--_-;-| '" | /'u)'- / --| / | / ) . / t -_L/ / - t---------------]_- z rEr- t\__-_--\!r\ t t o- ar - { - - - - ? j .-I 4r ff-r

t+ * l l *I I

Figure1 Illustrationsfstress,train, ndstrainorstress)states smodes f deformation'

While strain,e, and its mode of impositionduringthe processing nd serviceof metals s illustrated nsi*pte schemiticsn Fig. ll, thesecan allcorrespondto different temperaturesor rates of straining(i: cle/ctt). onsequently,ll theseprocessesremul-iifunctional and parametric interactions mplicit insubjectinga metai to differentstress, o), strain (e)'st.ain raf, (6), and temperature,7) can be describedin a mechanical quationof state:. lcto\ . !y)a; * (*)ar (r)do: \E)d'* \or / \dt /or in a functionalsystemof strainstateequations:

lo : f (e, , T)\ (uniaxial)

54 1and their alteration(or evolution) with deformationprocessing.At high temperatures,h-es9microstruc-iur., ut. alteredsignificantly y annihilation, ecovery,or growth processes.Correspondingly, he perfor-mancedata s changed ccordingly'Figure 12 and 13 will serve o illustratesomeofthesemicrostructural eaturesand act as a basis ounderstand therelements f the mechanical quationof state.For example,Fig' 12 not only illustrates heconcept f thermal ecovery or graingrowth),but alsorecrystallization,vhich s depictedby reverse rrowsindicatinga grain size eductionor recrystallizationothe righior grain growth to the left' Actually graing.o*tf, "utt foll,ow recrystallization as rvell'h.ecrystallization will occur when grains are"def6rmed" significantlycreating a high degreeofinternal (stored)energywhich drives nucleationandgrowth of nervgrains.This is a kind of grain refine-irent, and can eitheroccur by heavydeformation atlarge strains)such as in wire drawing followed byannealing t elevatedemperaturecalledstatic ecrys-tallfzatii) or by clynamic ecrystallization,where theprocess occurs essentially simultaneously with theieformation. Suchdeformation s said o be adiabaticbecause t creates ocal temperature increasesvhichinduce recrystallization.Such adiabaticdeformationrequires igh strainat high strainrate:

L,T : Kei (3 )whereK is a constant.Often extremelyhigh strainingcreates egionsof intense ocal shearingwherehighdislocationdensit iesnucleateverysmallgrainswarethemselves eformed.These egionsate calledadia-baticshearbands.Figure l2 also illustrates some rather obviousmicrostructuraldifferencesbetween BCC tantalumand FCC copperand stainless teel' n addition' theannealingu'irusn copper'whichcontribute o its char-acteristiJstraight ani parallel boundaries'are alsocharacteristi. f th" FCC stainless teeland especiallapparentor the arger-grain tainlessteel'Thesewinbbundaries respecial oundaries aving ow ^energYncontrast o the regular grain ^boundaries20 mJ/m-'compared o aboui 800;J/m2 in stainleissteel)andareco inc iden tw i th the{ l1 l } c lose-packeds l ippin FCC metalsand alloys'These eatures'of coursealso contribute to fun-damentaldifferencesn themechanical ropertiesof BCC and FCC metalsandalloys(see ig.-g). Finally, with regard o the microstructural eaturesevealedn Fig' 12'we shouldpoinout that the surface tching o reveal hesemicrostrutures constitutesa u.ty o1d and powerful techniqu

d'-d . =:o o , q \v=_ l * lPeiss6n7 Irotroi-v/ / |t t Tvu*u.2TRIAXIAL

f)ttorsronl--{--- rotioue)

lo : f(e,i, Z)lnr (triaxialor multiaxial)Suchequations an be writtenas so-called onstittttiverelationstrips hichcanbe teratedon a computer or arangeof pio"... and/or performance-ata to modelamanufacturing forming)process' t low temperatures(near room temperature)orming processes re veryiependentupon microstructures suchas grain struc-ture and size,dislocations, nd other defect eatures)


14/38

542Mu

Figure12 Grain sizech " ' E(*.. ',.raitarm,n .'i.i 1.'fiiff # :j Xlll:;f f::ll* tionri h)o gan: ronmicrosapt',o..., fJl}*fYtl ::d (b)sh w.opicalmicrographsftantalum, hile c)and d);;;;;;#:,;;XliJ:jli1tion (right) r grain rowrhrerr).a)and b)tronmicrograpr,r.-o....pondingrograin tructur::::,:,p:i"il,Tjcrographsles n (a) and (b) respectivelv.called light metalloqraphy.Selectedetchanrscreateurface elief which;.,',X,,",1*#ffil":;",TJi1,,iJ"'1,#.".::1"ff;:^-.lljo-n!."st to Fig. 12,\iF,l3 shows arious islo_arronmicrostructures.witf,in iriliJ;. grains nesponseo variousmodes f d.i;r;;iJn, in"tuoinn

i,Ti1",Thecreation j highdensitiesf suchdisloca-rons reares subsrainJr_rit. _i";o;;r;;;"r" whichan also be regard-edxi:fFffiil:; :: "l[xi"-'i,1i,iff:,ornred r unprocessedmetal: -"- vrr6'ro : oo+ KD-t/2 + K,d-t g)


15/38

543Industrial \{aterials

AK,o.ll,n

\ . tt \'to\\r. \tu\..\

0 . 51 2 5 - , 1 0 npt/2(0ccni)-

whered is themeancellsreellustratedn Fig' 13'This"qt"ii"t is a simplemodificationof the Hall-Petchil;;i;; shown in Fig' 5' The constant'K" in Eq'(4) can vary in ,.rpoi'" to the thicknessof the cell)7r, &"",Jd aK' in Fig' 13' The formationof suchairiiritio" cellsndeformedmetalsandalloys s a con-;;;;;;;; of multiple slip (or slip on.more than oneolaneor parallelsystemof planessuchas on all fourii'tr,. ii f il pru*i shownsaThompsonetrahedron

t 'Il 6I\\ - 4\F\g\\

0.1

, 0 1 0 n 3 0 4 0 5 0] PQeal-Figure 3 Dislocationellstructuren copper ndnickelnfluencedy stressndstrain. a)coppershockoaded t a

peakDressuref l5 Gpa plane tress).b)cast.opp...rod -ultiaxialtr."rl t.icopp". rtro.t loaded.af0 Gpa or comparison

itht").(d) coppershockedepeatedlyt 15.Gpa. ti. tr,. wide and tti.tiaii"""ti"n^ce]l lalls (aK') in

contrasto (a)'(e)Dislocation ellsizea u.rrri Jirtocation ensity io, a.u*n andshocked1 "1a^ryi (f) Reciprocal islocationellsize

ersuplane_wavehockpressu'rl*1"s"rrtri"ru andNi. [Data n (e)and(l) afterRef.2'l

in Fig. 9) and the formation of a kind of equilibrium;;;;.;;t both within the cellwall' and in establishi.g itr"" "ff itself. Thesearrangements ependupon theu,iro",ior, and repulsion of dislocationsand minimiz-i"g itt.it ,",a1 iniernal energy'Consequently'ncreasing thestress r strar" increiies he dislocation ensitand this reduces he sizeof the dislocationcells'd' In;;;,, ;;. (4) K'/d - K" J1yher.e " isan'*::l:,i"",-".4-, is the dislocationdensity'An increasen

i,L/

/"; ' A/ . , / '/ . /

'./


16/38

544temperature duringdeformation will cause he cell wall tials sen*oto.r L.. r^_ - -

Muthicknesso declinei,"1 ..1"h""irr;;il" sufficientty o,rifflu,ed bv rong talki,nsaurts.when hiswi:trtHl"iTilT::'t r"el"'p"'uiu'e,"un.u."o."i.ir*o unor,.,ni"ri]iru.,ur"ischaracterir.J:*:tffilf;i$,'"",:',y,*hi::;*,r:xii*:k;tJ,i.;*T*1,.^:i."ei""ri""copper ndnicket.rti, a'"irlr,;;; "":#le ror both tttri"n"In ,.n; ;';J,#er tvpe or crvstaldereof microstr;;;;'evotution for severaltmonfeature cation_cells.of course" 'flff":i:'::j*, likedislstates sweilasr,."*1,""r,:;: Y:I"j stress/strain coincidenii;;i,':ji'^_"tt,srnce theseaults r1'r'h" B'n","ilr',!1":Til'ilJ[:i#*i#;*#fi;iiffi''}iiii]j.fti#tl microslntclure ev,air"."nt-.tr.rJ'rz;"ii*"* forcopperhockoaded-at .i""ii", faurts.ni, ,ir"ti*ship is mpricitn Fig. +l:l:"ili;i;'"#:"fi:"f"t",1i,".t91'XHi:.1Y-"'a. "r'i1 919'rv'i'**"J'lneimpre,eriodiceom:':::_ti,h ncreasingtressrstrainorainililt"l "?ll trl fo.r rr rt pra'e ilioti11i:i,'fi:r,:'{:,t:lilr".:;.;ll"iFTF'.iffigi,}i#;ilh*i,'i:tfr*tructure volution*" "ep;;; ,"^inr^,l"tr;: fi[::: (splitting)into two p"ariluiairro"urions.A fewexam;:H".i',HT,il:,f'u q: ;;;;;,'"ni'Jumetars::'r::;' #:8ffi:j"llir";?:il'y,i:il"j#rji::::iiiiiiiiii ::..::::::!::::!,?notherrwhere,snBcc,'"i;ip;rii v,t".,un :ii!!iiiiiii!! !i!:ll!.t!iiiiii!!!!!e ctivatedFie' )'r"*,,"""* ::"":,: .;:ii i*l!!ii i i: i i:..f+si:$#;iii ^ne abi l i ty f d is locat ions. tocross_st ipn Fcc : ! i : : : i i : i i i i : : ! ! ! : : : : : : : ro- r i i i offit:,1'aJ1,ll',ilo,o"i1j1dtherl"*'i'.0 auovs, ''i;::::::::::a :ii::::!:^iii:::ii:trJT;l'l'*"i:i.**'1:"f:,,ffJ,1"1:fTj:i,::=*,o,,,="#".;*;;;.hatgrain ounaaries'-.t#;1ffJ"""11J;1r"iTr"J .*-.S#p**^ e=o(rr?)/6=o(112)/6i:":Iitrfi.,'rei?ilf##J#:#1?r;:ffi*#i:di*,'*nr.:*n"."xf",*$itiffi be distocarionine)aG(b)2 (5) wsffiherea is a const"ll^r!*h will vary for an edgeor oActcrroB-otornsc-qtornrtffit*ffifif*ltffififfian be lowered by Irfr:#*K*5*t*lf,{"ffi

cregion(planar nterfa'rii pri'""J,;ffi':::1,'JJ":'illTr rlpranethel1q-1*"."or the tr r it ptan"s;il ;'";:r;';";::; lqr:,r:^"y:maticdia'ramsdepictingthecreationorparnese tackingaults hereforet;-;;r;;; rir;i;;"^ I"I gtrf:;11'"nsnd..stacr[i-r[lurtsn metarsndarroys.ta)specific in terfacial freeil:iT[:il:,";T#,;"":#*"1f,,]1il#iTe'*frtd.{ifi,ji-fi-'#ffi'j.:;ii?fT,;T:',"

.n*. d

high stacking fault' -vuevYqvu'v' rn metals with o 's!vu uv a reglon ol'stackine fault (6). (b) periodic atomic::l-1:'iffifi;-ffi[,;,['fl_''j,H,Ht,i #:i",:i]]"1.66,,rx;*l[ l#h:::nergvmetals,hedislocation,fo#;;;;;;:'j'a*,':"" or stacking""ro, i"-ioi';;;il.r. steer trained yo n ten_..,c


17/38

IndustrialMaterialsplesof extended nd overlapping tacking aultscom-monly observed n deformedstainless teelare alsotn"JilLItt;#ti,rr" cr,8o%i,balancee) ro-videsa good example or stacking aults in Fig' l4cbecauset has a very low stacking-fault ree energy(yse) n contrast o copper. n fact FCC alloys nvari-uUty tuu. lower stackingfault free energies han puremeials,and this feature s illustrated n Fig' l5 whichalso illustratesa very important aspectof adding ormixing metals o form alloys.Even dilute alloyssuchas Cu-Al whereonly small amountsof aluminum areadded o copper the aluminumsubstitutingor copperatoms)can pioduce a wide rangeof stacking-fault reeenergils und, correspondingly,a wide range ofmechanicalbehaviors and a correspondinglywiderangeof characteristicmicrostructuresand microstruc-ture-evolution. A simple analogy for the effectsofstacking-faultreeenergyon deformationbehaviorofmetalsand alloyscan be seen rom the cross-slip ia-gram n Fig. 15.Extended tacking aults can be ima-gined o resemble hook-and-ladderruck in contrastio a small sportscar for higherstacking-faultenergy

Fcc'ErALoRaLLoY:'11"'3il'*,*"," li"i""t,,l,l"irli"t'""

545which, when driven by a resolvedstress o,,) n theprimaryslipplaneduringdeformation,can-more asilynegotiateCross-slip.his phenomenon,when consid-"r.d in the contextof themechanical quationof state[Eq. (l)], can reasonably ccount or the mostpromi-nentasfectsof themechanical, s well as thephysicalprop.rti.. of crystalline r polycrystallinemetalsandalloys.6.2.2 Alloying Effectsand PhaseEquilibriaIndustrial metals are more often mixtures of ele-ments-or alloys-than pure elements uchascopper'silver,gold, nickel, ron,zinc,etc.Exceptiorrs f courseinvolvJmetalssuchascopper'as discussed reviously,which is required in a pure form for a wide rangeof commercialwire applications' Recycledmetals'which now constitutea hugeportion of the industrialmetalsmarket, are also largely elementalmixtures'Combinationsof elements reatea wide rangeof newor improvedproperties r performancequalities'andeven mall elementaladditions to a host metal cancreatea widerangeof propertiesand performanceea-tures.Exampleswhich come readily to mind includeadditionsof carbon o iron to createa wide rangeofsteels, nd smalladditionsof copper,magnesium' nd/or siiicon to aluminum to create a wide range ofstrong, ightweightalloys.In order t9-fot- an alloyit it ti"..t.ury that there s somesolubility of oneele-ment in another o createa solid solution'Some om-binationsof two elementsorming binary alloysarecompletely soluble over their entire range of mixing(O-fbOX)formingcomplete olid solutions; or exam-pl", .opp", and nickelot "opp"t and gold' Suchsolidsotutionscanbe eitherorderedor disordereddependinupon where the atoms are located in the unit cells'Figure 16 illustrateshis concept as well as the pro-found effectorder or disordercan haveon propertiesuchas electricalesistance.Solidsolutions uchas those epresentedn Fig' 16are referred o assubstitutionalsolid solutionsbecausthe two atomssubstitute reely for one anotheron the

latticesites.Of coursen thesedeal formsof alloyingas n manyothercircumstances,he relativdsizes f theconstituent tomsare mportant' In addition' heelectronic structuresof thJ elementsare important indetermining ompound-formingendencies swell asthe actual structural featuresas illustrated in specifiunit cell arrangementse.g.,Figs 3 and 4) 'Phaseequilibria (equilibrium states)as phase elationsdescriting hemiiing of two or moreelementsocomponents hi.h b.huue as singleconstituents) re

A INio,Cu-s . Al 'Cu-l0 ts. Al'Cu'30 # znStalnless Stol

(18frC.. gwNl, F. b .I f f . )

r 6 612 8

2 0

1 12 1

I . II - rI - - rI - - - - - rI - _ - - - - - - - - - - - - - - - - - I

l - _ - _ _ - r- L - - - - . LF 8' -r

Figure 15 The concept of stacking-fault free energy(ysp)un'd t, influenceon dislocationdissociationand cross-slipin FCC metalsand alloys.yspo< /6, where6' is the separa-tion of partials. For high stacking-fault reeenergy he par-tials are very closeand cross-slipeasilyto form "cells'" Forlow stackin!-fault free energy he partials split widely andthere s little or no cross-slipesulting n planar (straight)arrays of dislocations.*Aluminum atoms substitute or"opp". on a corresponding asis' Data from Ref' 3')


18/38

s46

I

Figure 16 Order_Disorderphenomenain a simplebinary.olid_solutionalloy. (a) eu.._.."i"#luUi", AirorOered0fi:;':l# fu].,f,ace-centeredubic, 'J",Ja.sou:50Au. c)50cu: to o"'*o11T,o,i;:f|!'*: orderednooisorderei

:,":l:tl"d.br "o":llgi]"T thermodynamics,andcanbersplayed in a vai:hic;;; ::+iiftr:;:tr:tr,T,:::;;,r::,!j:!*,:, Eeuilibriumil;;;t": impriesaria_rons f temperature(Z),n.".-r-u-i"filno "or..rpona_ll*.I?,t1.:. (14; r_concentrationsn' *componenrsn rhe systemexpressed s either jrn, percentortomic percent. n nig. 17 "u.i"t;";?f t.mpe.utr."and concentrationare.shown , "onuuri (or standard)ressure (260mmHg). Equilibrium boundariesashaseboundariesi:*.*_;"*il".i'*i^:Li:":11T'r;'J:111#,];;*rnarronshere he.metalsr" .("iifl in the iquidtate nd mmiscibleinthesJid "îf,ir,"r/rc forms,sllusrratedrr*,.Î 1oJ:;#;ilirisci bitiyand 1l att. l7c for puriiulsolubility.b".p"""a, also orms a consequenceof the air".ences'iilatenc.s. theore-etectropositivethe one "[;;r;'u;d the morerectronegativethe other rhe gt;;r;;;. ;e tendencyorvardompoundl:ryu:i

-dil;.rr,.*,may eorned by comnound.s,as- hown n-rig.,izo. Since, shown n the ieriodic,tablij;,rig. 3]Eerlmentsin thepper left portion of the table are"thl rirJst etectropo_itive n contrast o those.elec;;;;# elementsnhe upper right, the relativeb.h;;;;^;; phasedia_ramscanofrenbeestimatedh.;1"il;into account$:i:f :'fi ;:i;j #rovicilil: #lrauv, ,,ovsuna.ir"ruii"-,.#,'j'r"'#:#''J"":;:?,i#rTil,,H:

MurA metal or element) f lowervalenceends o dissolvne of highervalerrce. lloys oi..f".rn.n,. havingtheame alence ut different ir", t uu"limitedsolubilitiend usually0",:",,_r:T ;;*;;;;: while eremenF[tfr:5t:ences in valence"r- .t"ur."rn''"""i,Phaseequilibria s-an important issue n manufacuring processeswhich invoi-v;'ffi ;;etc., nct rora.,. o"".";:::';"::lôrng to thin layersbondeduuron,oa:ln:ctions'Thin layersuna roto.islnat elevatedn6"t-uljlts are oftenprone to diffusionil;; ffi.d;T,':Tffji,HT,:Tl,T;reae "-There are, of course,more complexbinary phasehenomenaas shown ;. i;'"rrj"'i'n"r*. l7c whichnvolves different. crystal ,ri*ru."r, solubilities.l'illlili;ll"ilr"'"/""'i"'i'"''" "aai,i"',,0i,"l:Ta;;;';;;rugT,$;.,i,'ff:'".'re also commormateriars, "';t:.1#?:,#J":r*:::3 ll.,ff]quilibriummateriatsy.i"_r,-"nj iin*n, altoyngs a contemporarv example. ln tfri, prosorbrer n orbre#;;;ili.;;#i,l""1llrtHl"lllmixed r milledig.i1., 1,'ii,rrrl.ri.,"oattritororoduce mechanically-bonded,nn._pi*a". mixtureshich can be sinterid-*;; f"ri;;;:l,"ou,u sysremst high temperatureand p.essur"-.--figu."lg showsn exampleof sucha system nuoiuinlirngsten andafniumcarbideo_p"r"J rJrn "" .n"i,orium alumi-um alloy ormins,"f G";-;;:;iii1: ""to"unds ascomplexprecipitates6.2.2.1 precipitationandphaseTransformationsFigure l8b illustrateshe_formationof second-phaseprecipitatesin a dilute ,lumi;;;'lioy'1zoz+;, unohese eatures re al.r,o*niin;:;;;i{!!'l1ll,:l,lTfli'""#:il:lfrecipitationand phasetransformation"*tiUit funda_entalsimilarities: othcan ha""'"i"r"f""i or compo_itional as well as crystallographicdifferences nontrast to the matrix in wf,icfr' fr-eyoil. no,n ,nuynvolvedifwion of one-ormore elementshroughtheatrix ro thesiteof rutcteation,ri6;;;involve theass transport of "lor: inio n.*,"oili.idences byhear(stresses)or other i";";;;"il#; phenom_erta.These.aregenerallyrererreo " L'iiu"rionlessll1._rfol"3rions.he "r_"ti", .f' " "ri,i""f nucleusor precipitationor transformati", i, "i,* illustratedll":,,t^". shown n Fig.-I9,which nvolves he forma_ton of a new (sphericar) rt"* *iiii"^ u""-u,.,* u, "


19/38

547IndustrialMaterials

sr]--

F

e,

Figure 17 Binary phasediagrams. a) Solid-solution diagramfor Ni-cu. (b) Simpleeutecticdiagram for Pb-Sn' (c) copper-zincphasediagram.Singlephases reden-oted , p etc.resp-ectively.+ y is u *o-pitutt region'(d) Systemsoined by compoundformation n the Al-Ni itir. aiugrum. e) ron-carbon hase diagramportion' (Based n data n Ret' 4' )

consequence f either homogeneousr heterogeneoLtsnucleition. n homogeneousucleation, spontaneousprecipitateor newphase ormswhile n heterogeneousnucleationa surfaceor substrate rovidessomeaddi-tional energy o initiate the process, nd as a conse-quence the- overall energy to drive the process sconsiderably educed rom homogeneous ucleation'The volume of new phase o createa critical nucleusis also reduced n heterogeneous ucleation'as illu-strated n Fig. 19.

As illustrated n Fig. 17,phase ransformationsanoccur in moving through a temperature. radientatsome ixedcomfositioniand this is espccially otablein thecaseof the ron-carbondiagram Fig' l7e)whereheatingand coolingalter the constitutionof steeland'ultimalely, the properties.The iron-carbon diagramrepresents'he limiting conditionsof equilibriu-,19isbasictoanunderstandingofheat- treatmentpr |plesasapplied o steel "nttfu"t"te andbehavior'The'"onu.rrti^o.tuliron phase s BCC ferrite (a)' But iron

s(e).S(F)

r + 'GRlpnr tE sTAELE HASE), * 'r ,ur*r,r, lurrosrorae'ptt tel


20/38

s48Mu

*

alsoexistsas FCC austenite7). These arecalled llo_ropic forms of iron. wr,.n'a pio;;;;;"" sreerofpproximately0.8o/oulb:l i, ;;l; ,0"r",, from theemperatureranse at.which uur;;i; l.".tuut., utr orhe fe_rrite nd a precipi,"r" "iiC"utt.l ""n'.ntit.orm a newprecipitatephase."li l;;;Iu", which sa:1T^"9 structur;. ementite, *"turi"ii., und unecomposeinto iron and hexagonui*lior._pu.t.o(HCp) carbon (o. n.u.rt;i., ";^:::1: -t:.srowryil' #,:l?i,l'?;rfi:'in::il"n#;;,hase constituent at room temperature.Like the

' O.Sprnt a

,e'

Figure 8 SecondphaseRennedy,UTEP). (b) (Fe,particlesn a matrix. :c", ou sio.""ittil'ir1a) Hafnium arbide u.,i*:^i: a tungsten atrix(courtesyf christinea dilute luminumiloy (zoz+).ic"r?"r, #ilaria posada,UTEP.)graphiren a pencil.sheets j(OOl) carbon[actually0001) in theHCp structurel i ide ne ;;er theothero producea solid ubricant"'tre-ct'l;;,ii. tuuri"uting:1u1itfo{gastron ihich.m"k;;il;il"irarry us"rurnenginelock nd elated,*rr._" -*lffipu"ationr.Pl ::: 1".. u egraphi. p ;,,;;; ;;';j,; ;;;, onsoridubrrcant.

*,^Ot*yr. 20 illustrates-someof the more commonmlcrostructureswhiclotherphase h.no,n"nt^]1-rlteriz,e precipitationandabouel;;;i;;;ffiJiii:Tl*arbon auovsescribedsnolvs notherexample f iron_


21/38

IndustrialMaterials- 4Ttocu'a"

sf=1 [ ,I L'",o,..s\,--NN.," \a

Figure19 Simple,dealizedeatures f homogeneousa)uni h.t.rog"neous b) nucleation.AG, is the volume reeenergy, 5s s thesolid S) precipitate-liquidZ) interfacialf.e" !n.tgy, r isthe adius, ndQ" sthecontact ngleor thenucleusormingon a solidsubstraten (b)'

carbonprecipitates hichcan orm in ferrite'CommonprecipitatesioichiometriesncludeFeC..,Fe3C6,zlrdFe6C.Heat treatmentcan also produceother crystalstrirctures.Martensite s a common exampleand ischaracteristicof transforming FCC austenite o abody-centered etragonalphase or a body-centeredcubic phase. Martensite, like cementiteand otheriron-


22/38

s50M

carbonn solution.rt. rr.rt'rt, ffiilr"'.tt;:t*n allovs' a)Bcc *:::,:. yl:n^*rbon n sorution.b) FCCausreniteithlternatinglamellaeorrerrite-andce;;;;;;annealing twin boundaries.c) c.rn.ntit.-6".'r-C)precipiratesin r"rril. to iec*) n ferrite-vLrtretrLrrereatrngearlite'e)Graphite "t.r ro".r.ii"'i..ltr!lil IroncarbidesM4c6 and

tion-inducedmicrostructurethe greater the residual::::: "r hardness work harderi-"r1.'ir,"." featuresre rncremenraland "1n b: ittustrate"in u ,iigrrrfyAif_erent orm of Eqs. 4) and (6): ----*'" * "

Deformationcan tselfadd ncrementalstrength rardnesso a materiat ycreatinglirir""i,"r. or dis_f :i,:T,":ff dli,x1'ine.i,-ul';;* s ackigdeformation-inducedlti:*it]"n twins)' or evenaIl"::6";fi ;ilrL*,,#;T;;,ll,il';,,,,r_mg thegrainstructure:he_;;-;;;;',ilr. o.ror_n_ o : oo lx,x, _ mi (7)


23/38

InilustrialMaterials 55 1

Figure2l Sensitizationnd carbide recipitation t grainboundariesn 304stainlessteel ged50h at 25'C' (a)Mill processedp.t, to aging. b) Detailsof carbides t grain boundariesn (a) (TEM image). c) Mill processednd deformedn tension yitraining 20yoprior to aging.Note enhanied ntergranular orrosion n contrast o (a). (d) Detailsof carbides t grainbound-aries.The corrosionexnllUiteAn (a) and (c) s indicative f thedegree f sensitization.Courtesy f Julio Maldonado,UTEP')

rvhereK, is the associated aterialconstant or a par-titioning microstructure,, havinga meanspacing,'; ,andnt can vary from about 0.5 to l. Figure 23 illus-trates he general onceptof strengthening echanismsin classicalmaterialsscience, onsistentwith Eq. (7)'Figure 24 shorvssome additional examplesof thesestrengtheningmechanismsas strengtheningmicro-structureswhich partition the existinggrain structure.Each of the transmission-electronicrograph TEM)images n Fig. 24 corresponds o a region within apolycrystalline rain. They correspond o partitioningparameters, A, andZ in Fig' 23 (Figs.24a,b,andcand d respectively).It shouldbe noted hat microstructural artitioningin materialssystems lso usuallypromoteshardeningbecauseor many metals and somealloys) he hard-ness and yield stressare linearly related:oy: AH,where or pure metals ike copper,A=l/3. This isan important consequenceincehardness, s a manu-facturedproductquality canoftenbe mprovedby thesamekinds of microstructuraladjustments erformedto improve he overallstrengthof thematerialor mate-rial system.As a case n point, the W-HfC systemshown in Fig. l8a goes rom a Vickers hardness faround 600 rvith a loh addition of HfC to about1200with a 5% additionof HfC to theW matrix.

The addition of a dispersed hasesuchas HfC toa matrix as shorvnn Fig. l8a produces composite,often calleda metal-matrixcomposite MMC). Suchcomposites orm a unique class of materials vhichinvolve glass-reinforced lastics, ceramic-reinforcedmetalsand alloys,and othervariations.Suchcompo-sites can involve particleshaving a wide range ofsizesand size distributionsas well as fibers;eithercontinuous, discontinuous,unidirectional, bidirec-tional, etc. Thesevariations n materialscompositesproduce a wide rangeof new materialsand materialssystemsand applications as well as a range ofstrengthening mechanisms.Not only do fibersobstruct dislocation motion in the so-calledhostmaterial (or matrix) through the kind of partitioningas shorvn n Fig. 24,but intrinsicstrength s providedthrough the fiber itself n thecase f a fibercomposite'Very fine, single-crystalibersare especially seful ntailoring unique and very strongcompositesSiC inaluminum,BC in nickel,etc).For example,where on-tinuous fibers(f) are oriented n the directionof anapplied stress n a host (matrix) material (n) themodulus of elasticityof the composite E") is givenideallybyE,: EfVf * E^V^ (8)


24/38

552

{loF*

;sru=cCJoE

60cFigure22 (a) Invariantstrainproducing pecific,ntersectingaurtswhichproducea martensite ucleus.b) TEM imageof a, -artensitecreatedat strain-iniutta initti"t-t.i.*s shownr" r"il" ioq.rtoint.* steer. c) a,-Martensitevolume fra-ction tequivalenttrainordifferentttuitltui* ii"i.rot-.0 :oq ,iiir.r. iilt a.no,.a r"uiiil, i luiaxiat;, nd3 (triaxiar).d)tacking-faultnd psilon-martensiteodelsnF!c. -"1;.;;rt'G;i*rn ror-u,ionn {r l r};i;;, in FCC. I)TEM magesfeformationwinsn shock-loadedot-ri"i""r.rr,..r. --- ormationn {r l l} planwhich is oftencalled he rule of mixtures or-a binary where oJ ando^ are the correspon{ing fiber and;:Tt-:1n}fi:f,?:i."*"1fiff f;'sndingnber ;il vierdtrengthsstresses).correspondingbero' -';,r#;{,ili"r.;fijl: ,,"I:i"j,l"';;;,[fi,:::"1il":tr"j::,",r*espectively.Fromq8)tcane bservedhathe ierd ;fJfi{i1!T'i:'lll1liiffi['J,$ff[fr'J',#',:lTH:i.fli'rui:?riented'ber-reinrorcJ';;;;;-if,ili*:?fiif,:1,*yi",r"matrixhisisiear

Mu

o " = o 1 V 1 * o _ V ^ (9) E" = Ef E,,/(Vf E,, * V^E1) (10)


25/38

IndustrialMaterials

SI NGLEC R Y S T A Lo Y = o o

(a )I I

I . -f l l

I 1D- f ,. L . l J -

- L rI AI I

If ri p.L( c )

D

( b )

t t t t tI I I I I l .t , I " '

r f r r .l rr l r l - I l* Jj- r- r l r l1 1 1 J - J .1 r tr r f r r rr ? rr r i . r r l

l r l . t Ir l rI t J . l r tI I IIt r-. t- r( e )

t ao lo a

a

a a 'aaa aa a

o l 'o a

a a

Q .*-L.*

al a a

( f )

Figure23 Schematiciewsof microstructureartitioning/stingthening. a) Single rystal.b) Polycrystalline aterialwithlrain sizeD. (c) Polycrystallineaterialwith disloca-tions.141 olycrystallineaterialwith twinsor faultsspacedA. (e)Dlslocationellsofspacing) n polycrystallineate-.iat. tD Polycrystalline aterialwith precipitatesr disper-soidswithwearsPacing.

Thiskind of relationship analsoapproximatehecaseof dispersedparticlesor discontinuous ibers in amatrii as shown n Fig. l8a, which is clearlyan iso-stress ituation.6.3 CERAMIC AND POLYMERICMATERIALSUp to this point, we have reated ndustrialmaterials,.i.n." and engineeringn the context of primarilymetalsand metallurgybecauseheyare somewhat is-toricallyat the heartof the industrial evolution(andevolution)worldwide. n addition,metalscontinue odominate ndustrial materialsutilization, with metal

5s3castparts accounting or a significant raction of allmanufacturedproducts.Ceramicmaterialsare also asignificantmatirials componentbecause hey includeglassproductswhich constitutevery old and continu-ousmanufacturingand artisticcommoditybusinesses'In contrast o polymericor plasticmaterials, eramicsrepresent he extremen brittle behavior,while poly-*ar, ,.pr"t.nt theextremen "ductile" or plasticbeha-vior. Ceramicsarecharacterized y traditionalcrystalunit cells,whilepolymersareunique n their structure'constitutedprimarilyby complexandoftencontinuousmolecularchains.Ceramics re characterized y ionic(and covalent)bondsbetweenheir atomswhilepoly-mersare characterizedy covalentbonds'Both cera-mics and polymers are normally poor electricalconductors; some are excellent nsulators' On theother hand, the so-calledhigh-temperatutesupercon-chrctors uch as YBa2Cu3O7Qtttrium barium copperoxicte)which avesuperconductingransition empera-tures above 90K, are also oxides' Some oxidesaresemiconcluctorsnd simple structural differencescanhave a significanteffect.For example, he creationofan additionaloxygen acancyn theYBa2Cu3O7truc-ture (to YBa2Cu3O6) r the addition of oxygen ouu"uni sites in YBa2Cu3O7o produce YBa2Cu3Oscan havea dramaticiffect on the electronic ehavior'as illusirated in Fig. 25. Figure 25 also shows hefundamental features which differentiate (metallic)conductors, superconductors,semiconductors'and

insulators oth in terms of simpleelectronicorband

structureconsiderations,nd simple esistanceR) (orresistivity,p) versus emperature,T (R-T signature)curves.6f "o.rrr. the more popular and classical emi-conductor materials consist of silicon or galliumarsenicleGaAs), and devicesor chipswhich are fabri-cated rom them,constitutinga hugemicroelectronicsindustrysectorworldwide.q3.1 StructureandProperties f CeramicsCeramicmaterialsare norganiccompounds r similarmaterialsmixturesoftencharacterized y metaloxidesor other elements ondedby ionic or covalentbonds'or combinationsof ionic and covalentbonds'Theirpropertiesare often linked to the bondingwhich caninclude layer structuresor molecular sheetswith astrong covalentbonding in the sheetdirection' andweak van der Weals ot so-called h)'drogenbondingbetween he sheets.Micaciousmaterialsare commonexamplesof silicatesheetstructures'Talc is anothersheetstructure n which the silicatesheets lideoneover the other as a kind of solid-stateubricant'This

( d )


26/38

5s4M

- - . ' : . t-.r . ,-t**+

r r *r -1.St'.::lG.Figure24 Examples fruio"t'.-"tT;,"fi.1"1):LiF::Tl',ffii:'el'[ffi],[::jil:J?,,!,i;9,n.1,,n,rmateriarsa) isrocationersncoppeioxideispersedarticles2vot%)" ""-id'r'ri-r0Crarroy. ote irro"jf:'l,ll,:i l"lr.i'iolr t6 aruminum.d)Thoriumatronsanchoredon part iclea. r

1t_:1,ma,kes -abfn.o-yA.ers,sef1,,_1alcsheetstidingne over the orher.This s similar ,o ,i" Iff.., of g.u_hite lubricationrvhere he covalent-lr'f""O.Ocarbonayersslideoneover he. ther.This is rvl-atmakes astrons machineso easily,etc., as nor.J'pr"uiously.Many ceramicmaterials r" "ryr,uifirJo"ni t uu. ,t.u.-uresorunitcelts) trictrre iiil;;; it Jror* or,r,.ravais atticesshorvn n Fig. 4,-;; il;ral modifi_ationsof these undamentallattice urrong.rn.n,r_suchas thoseshown n Fig. 26. Fi;;"";"ro." ".ru_

mlcsarenot crystalline, nd have andomstructures.Glass n all of iti commonvarietiess thebestexample.Sonretimeslass s referred " ", " ?r"r#tiquid or aiqlid of veryhighviscosity.Figure27 llustrates omexamples f ceramic


27/38

55 )IndustrialMaterials

UN|TCELLOF YBarGuaOt UNITCELLOF YBarCu"O" UNITCELLOF YBarCuaO5

I vrrnuu; I arnrur'l: coPPER;Q oxveeN

vlEo(r

oEEoE.

VC

.-t-----r- c--]--" l - F "--\eF_ %SEMICONDUCTOR NSULATOR

Figure 25 High-temperatureceramicsuperconductorand relatedstructures llustrateexamplesof metallic conduction,semi-conduction, and insulating or very high-resistance ehavior as well as superconductivity-Resistance-temperatureiagramsillustrate correspondingsignatures or thesekinds of behavior. The simpie valence-conduction and sketchesbelow showfundamental electronic considerations. n semiconductorsand insulato., un "n.tgy gap (Eg) shown must be overcome'Temperatureprovides the driving energy n semiconductors. he (oe) structureshown top center s "ideal." It cannot exist'Only the (Os) structurecanexistl Resisiance-temperatureignaturesare shownbelowthe structureswhich are deallystackedperovskitecrystal"uu., i*l rig. xl. c and z in-bottom sequenceenote he bottom of theconductionbandand top of valencetand, respectively' n a metal, thesebandsoverlap'

YBa :Cu rOz

T(K)

METAL


28/38

556Mu

{ NaCl(Nio, Structure (cublc)Mgo, Bao) 4""?,,tg3;t"recubrc)

ZnS (Zincblende/Dlamond cublc)Structure (Sl , Ga As, BeO, SIC)IJ"";"1irtf',"rructre (tetrasona)

,"'il:.,[13::'li],f"u"'u"t",0,", i;:il;::'"J;;::':[., cubrc)Figure26 Examplesof ceramiccrystalstructures.ffil i'1'13rt;iti'^::^3,":'n:'""" highmertingt.v high-tempe,a;:::T:,X1ffi:":#';lruleramic engini materials ur" u "uri"ri, focus notnly in the automotive ndustrrl jri'""rrspace and^ther reas nvolving.materials-una aJ"", requiredto operateat vervhigh emperr,rr" f OOri3000.C).In additionto beingard, .orf ""lu-ics, incruding_g$:: ".: verybrittle..lni, *"onr;tra,;; is no plas_l'::y-1y veryrimitedelasticb"huui;;. M;ny ""ru.i.,lju" :"rV low fracture toughness . u .onr.quence ofhese eatures:heyshatterwith i_pu"t. inihe contextof crystaldefects iscussedo "artiJ. ,i"iionr, ceramicrystalsoften have u".y 19* a.n.;ii..-oi"jislocationsand therefore annotshp;hencq-ih-.;;iltr,; behavior.on theotherhand, hecreationof systematicacancies

tn atomic sites__especiallythe.cation (positive on)sites n.the crystal atticecan significantly lterotherropertiesof ceramics-.o_" ""iu_io'miteriats wittrood semiconductingbehaviorb;;; inluratorsandconduct ssentially],ur,."o_l;ffi i'*ll;3'ffTTHffi::."nd cation vacancy'i-pr"nai.;;#";r"ffi:":fiffi :f n,;:::::;any rystallineeramicsxhibit wije.uig" of opti_al properties having "";;;;; lfprcations.Substitutionalelements, gf"rr". """""", ii, theircol_-:.Tut y..tta.s pticat ropeiti", n ir-pioiochromism,where he degreeof transparencyor opacitychangeswith light ntensitysee ig. 27y.' - -' '-"rvranyceramiccrvstals,ncludingcommon quartz,exhibit a connectitn between polarizability and

rl-o*j " - 1 r

' { Y--lf:jsi'L i-'t)--IO


29/38

5 5 /IndustrialMaterials

Itj o ii) oO N O N

?,1(:) i:; oO N O Ni.-)o (l) o

stress(SJ)+r - r ' . ' . n\-,/ '..' \-/N O Nz1 ,l : A\-,/ .._,' -/N O No i i o+stress(:2)

l'd',ta,,\-/ +c(:)?l,iI n\J .,...i!:)

,o.lF. . - . r lo l,3v ax l.-.;-Ls i=T

II-o -si -o-IoIn,I_ a1l ,.ot tU

iijaio2 isi'4. o2i^ai, Y - - : bA^ ;4g+*6tfie{cu*

ph-sic bac.(rg

e

Figure 7 Examples f structure-property-perfonnanceeatures f ceramicmaterials.a)Piezoelectricrivesystemor scan-ning unnelingmicroscopeleft) operates y applying voltagev) to a perovskitetructureo cause orrespondingtressordisilacementi(right).u) pirotoctrromic fieciin-gtass.uur"dby light-inducediu) intervalenceransfer.The shading orre-spondso darkenedlass.c)Polarizationmagneiic;f ferrite.yttutt in magneticape ecording.d) Lightemitting, lectroluminescentevice.e)Ferioelectricight valve lead-zirconate-titanateeramic)(c)and(d) are rom Ref'5']mechanical orcesor stress.That is, a stressapplied biting this property are also termed ferroelectricalong somespecific rystalaxis (direction)can create materials. his ilectromechanical ffect s reversiblestructuralasymmetrieswhich polarize the structure. That is, the applicationof a voltagealongspecific rys-This creates corresponding lectrical oltage-a phe- tal directions n ferroelectricmaterialscan createanomenoncalled hepiezoelJcficefecr. Materialsexhi- corresponding isplacementr a mechanicalesponse

recdd sErol lN-Pbybck sErd Ottf

Ki @/ Y- [ Ilight50urce


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558as shown schema.ticallyin Fig. 27a.Micropositioningdevices utilize this princip; ;;i.'""celerometers,transducersetc. measuremechanical orce throughelectricalsignals reated,..,., t.f-.Jnverr a mechan-ical forceor soundpressurento an electricalesponse.Ferroelectric transparent)materialscan alsobe usedsopticalswitches r filtersUyuppfyrng nelectricieldo polarize he structure,treieUy^aeReitingor absorb_ing light (Fig.27e).Figure 27 illutappri-ationsi ;:1"# ffiiJ ii :::ff:i:'"#lics n a varietvof forms_sofia"r,orou,materials,l?:::, etc.areespecially.f."tiu"'rrr.fiul inrututo.,n,ti$lJ',, ", "lltr'lryll'"t'"t'i"uin'urto"' pu."thermari",rr",i"l,ILT;:,":?T'"",.*J;:',Hj:,:

_9::-:. o,t":elsing normally involvespowoe. proces_iii;x":ll?fJf:,,i;i.T:,,:f,."""":flrffisuspension,swell assol_gel ro".Jring of powdersnppropriate slurry gels. beramics ar! proAuceainoldsor cbsothershape or.r. -- -' -6.3.2 Structureandpropertiesof polymersIT:: ::" jwo genera.llasses f polymericmaterials:erasromersor rubbers)andprastics.piu.ti",are urtherclassified sthermosettingiastics(r;;;; epoxy esin_based.a eri rs) nd n i^ i t ^ i r.;i;;o*.r, canbetretchedelasticallyo.verextendedelongationsandhen relaxed, essentially .turn -tJ'lt eir originalshape.Consequentlyther! rnoy f" ;; ;;._"".nt (orlastic)deformation.ptastics,in iir" "in., hand,canhavea largeelastic angeor evenan elasticJikeangefollowedby an extendJ,u"s; ;i;;;;;", deforma_tion prior to failure-h.n." ih",*--pi.rri"s. plasticshavea srructure imilar o grurr, ;;';i.;_inated byhainlike molecular arrangements.These molecularchains an be oldedor braiched,ura ,il""un accountin part for thedeformationU"r,avioloifi"rti"r. fn.r.molecular chains are b.onded r""f.",ii_a processi: 1Io n ':. no rme.1zlo . Co;; ; n po'ry..,r,ur"rynave a -corresponding rystal st.ucture. The mosteneral eaturesof ooryme*t.r"tui.-ur" illustratedin Fig. 28 .Like ceramics,manythermoplasticsaremolded byinjeuion molclins\ from powdirs to form products.

|l.:::llng plasticsofien provide "-;;;; or matrix:ff:fr::":"j;iH"",'.iliH":;::lns[:il3ll.:l containingofr' .';bb;, "liopJn.n,, rroroctuceplastic compositeshaving u ,ria. range of

Murenergyabsorbance, tc. plasticsheetcontaininghard;,:.;It" particless alsoutilized n novetwearapplicaTheautomotivendustry s oneof the argerusers flasticmaterials,.otl lhe;To;"iii"g' "ra thermoplastic.A modernauromobil.of"r, uilitJ,not onlyof essentiallyu"ryLin;';i-,::lTt"TH:,:metals,alloyssemiconductors,".rurni"a,plastics, ndomposites_butalsoa wide u"ri.ty of eachof thesematerials ystems.Figure29 show-sor comparison he tensilestressstrain behaviorof a "_o-TTinpf"rri"'t"r"rial (poly_methyl methacrylate, MMA) ;;;;-;'.unge of tem_eratures omparedwith somecommonceramicandmetallicmaterials. hiscomparironnoionfy illustratesthe unique mechanicar to;.;r;';r"it.." materiarsbut also their comple-"nt"iity ou.. u^rvia. rangeofemperatureand stress nvironments.

6.4 -CREEP,FRACTURE, FATIGUE ANDRELATED INDUSTRIAT TVTATNNTAMPERFORMANCE ISSUES6.4.1 Creep n MetalsandplasticsS::t is-apropertyof metals andalloys)and ptastics\vnereprogressive lastic or permanent;'d.formationtakesplaceover a long period of time t some ela_tively constant oad or,stress.n effect, his is a time_,ojl"_"9."1 strain (or.elongation),;;;' is particularlyrmportant or materials peratin!at "t.,nut"Oempera_ture where he creep ate (or sta-in ate, ) is acceler_ated.Creep atesaciuallvuurv,iii- ri_", *o a typicalcreepcurve or a metalas shown n Fig. 30ausuaUfdemonstratesthree,weil_defineJi#. *?0,"g to frac_ture: primary, secondary,and tertiiry "rl"p. nrirnu.ycreep ollows an instantaneous lonjation (or strain,ea) and representsa stage where the creep ratedecreases ith time..s."oiaury fi."p'"r"pr"r.nt, usteady-statereepwith a constant r..p ,u,., while nthe third rtug. oi creep he "r.;;-r;;;;iiary u"""r"r_ates o fracture.As in other aefor_atioriprocessesin:,.I:l"tli". or polycrystalrinemetals ; ;iiJyr, disroca_trons lip o allow or straining

. Cr"-.p in plasticsalso occu"rs t elevated empera_tures but does not occur in discrete tug", b""uur"the mechanisms differe", i---".i;Jl# metalsoralloys,as shownon comparingFig. :0" ""a b. Creepof polymericmateriarsr rrt"rL""".;; #" so-cailedcreepmodulusdefined s he ratio of tne#tiat appliedstress, s, to the creepstrain after a purii"uru, ti_.,e(r),andat a constantemperature.lasticswith a hieh


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5s9IndustrialMaterialsT Tr lH H(c2H4)li:il-li-[]:thylene PolYethYlene rondom

#ternotinsblockgroft

homopolymenchoins[s ul1j-:t

po lyv lnyt ch lo r lde Po lyPtoPylene(Pvc)

CH,I-c -\,,oocH3

Jilr-i*polymethyl methacrylats(PMMA)

p o l y t e t t a f l u o r o e l h Y ls n s( T e t l o n )

T T T T T T T T Tt i l l l l , \ l l

Ji-i-ll'ololystrens

aHr\ agr\ aHr\,C:CHa ,C:CHa ,C:CHa-cHz cH2-cH2 cH2-cH2 cHr-

natural lubber polymer chaln (n=3)

Figure2g Structural ormulas llustrating ovalent onding n polymericmaterials longwith simpleschematicepresentationsof polymersand polymerchainstructures.

copolymdrchoins


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560

stroin%) 30Figure29 Tensile tress_strainurvesor several ifferentll{,nl*int materials r various *0.."i".... Temperatureegrmesreshorvn ariouslyhadedl Urrla.porymersareommonly sedn a variety f t"ir_rigr,t.i..ior..

creepmodulushave ow creep ates.Whenplastics reeinforcedwith other nu"r.'o, Orp.r."l'pr,ur"r, tfr"reep atedeclines..e,.,he "r""p _JJ"iuJi, in"."ared.For exampte,nyton rrls a_9re;n^;;qfi;'of aroundjfr9.*5',ffi;::: =''o: *r""r n vrparithe samenylon, "onrrtll *nile the- reepmodulus or:5d;,: ;;ff ;: ,:Hi::jI3il3]ll,,$ :estconditions.Creep n metalsand.alloyscan also nvolvediffu_ionalphenomenaand ..sliding,,of subgrain tructures

Mu:,1._.:.1tiding]l;y,$arrv smallsrains,hat s,stronggrain boundaries , oppor.jto sl,p ,; ;# :rystalplanes n the-matri_. rr"m.iently high temeratures,someor all of thesen..t unirrn,maybeverrominentAt tem_peraturesin "*..r, otf,oiiifr. ,.ir1ngpoint r > o.;_r,;,+;;;il;i ,t.rin,canchieved n ordincommonly.p..rii{ ltnsile esting'nis phettomenll :i** ;ffi;:.g,:'fiy,!:;"y,!;:,.l:il::irren concurrently by rotat-ion,-oi ,muff grainsuperplasticity is . arso--*;;;;;;" dependenor : K,iT, wherem is called l;;;;r*exponen,an he ubscript.;i.; ;'il: :HT.'.':il:lspecifico the straining.It is probably nstr-uctive o look back retrospectively at the mechani""i "qr"ii"i"ir'r,u,", Eq. (l).his equation llustratestur.ols ih ;; (2)l that forny particularstateof stiainiig fo, .t.l.rl, deforma_tion is very specificaily ;;;;;") il; not only thetrain (e) and strain rate (i), Uut ttre iemperatureathich the strainingoccurs.

6.4.2 Fractureof MaterialsTensile ractureor breakage-involving he separationof solidmaterialsoccurs n alt kinOsJf materials.Weoted n Fig. 30 rhat.fracture;;;;creep defor_ation.Fracturecan.be h"."";;;;;;; *un, mareri_lsby two extremes: "rtitrTrorirrii,i"j"r"u extensiveplastic deformation, lnd brittle lroriur" involvingessentially o plastica.tor_uiion.'i.l",ur" involvescrack developmentand propag";;;;;; in this con_extductile racture s crraractei;;;;;r1", crackpro-agation,whilebrittlefracture , "i#.r"rized by veryapid or catastroohic rackgrowth.B.;il fracture netalsncludesLurru^g"r separation n specific rys_al planes.However. o"rur.ln'i",r.ri"",rrre metalsan also nclude ntergranuta,uritu" f;;;;;r" on grainboundaries.This oftgateo he rain":H"TH'"IfiHyil*ilff;energies r thecorrespondingint.riu"iui f."" "n.rgi.r.Low temperaturesund u..y"rupia l"r"r^rr strainingsuchas impacr tend to ruul, uiittr. f;;;;r", and as_Y^.,l.nri9l.d previously,-some,,..1, unJ o,hermate_nals exhibita ductile o brittle .u.tu." t*nsition ashe temperatures decreased.his is utro tru. of plas_ticswhichalmostuniversally ecome e.y .ittte as t eemperatureis owered.9*;.i"q;;airs'e litneir gen_eral lack of plastic behavior, "f* -"t "#eristicallyexhibit brittle fractureover a_wide rangeof tempera-tures Modern desisnstrategiesor celmics in factincludeefforts o i.iprove theductilityof ceramics.

tnoU)

Figure 30 Idealizedcreepcurve for a metal (a) showingnmary, secondary,"0"_,.lliur, "r..0 ,;;;;'marked l, 2,, respectively.e1 s the, racturestrain.Nole-thatthe creepates i : de/d0'aredifferent.in,fr.*fr......i stages.n (by,n- dealized orymericmaterial ik; ;;l;.-,rdi.rt.uin, *ttt,lme n a somewhat ifferent ashion.


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IndustrialMaterialsFracture modes suchas ductileor brittle fracture,etc.) are implicit in the appearance f correspondingfracture ..ttfu." morphologies (or fractographs)andthese eaturesalong with simple fracture mode sche-

maticsare illustrated n Fig. 31.Note in Fig' 3la thatductile fracture is a cup and cone feature originatingfrom void developmentandcoalescences he materialnecks.Shearfracture is a geometricalmodification ofthis process s mplicit in Fig. 3lb' Figure 3lc is illu-stratid by intergranular brittle fracture of iridiumobservedn the scanning lectronmicroscope'6.4.2.1 FractureToughnessToughnesss measured s he amount of energya mate-rial can absorbwithout fracturing. Fracture toughnesstestingconsistsof impacting a notchedspecimenromthe rear of the notch with a hammer which swingsonan arrn (a pendulum) from various heights (&) abovethe specimin. If the energy s consideredo be thesimpG potential energyof the hammer (mgh; m is t}re*utt und g is the gravitationalconstant), hen testingover a rangeof temperatures an ndicatewhena mate-rial is brittle (lorv fractureenergy)or ductile (high frac-ture energy);or the appearance f a brittle-ductiletransition.6.4.2.2 FatigueFailureof Metalsand PlasticsRepeatedor cyclic stressingof materialscan causefatigtte racttu'eat stresses ften well below the static.tt."tt required or fracture.Thereader an elate o thisphenomenonby taking a steelwire-whichcannotbeiracturedby tensile training,but whichcanbe brokenby bendingbackand forth. In addition, f thecycles fbendingbick and orth arerapid, he materialwill alsobecomehot, and break sooner'This heatingoccursasa consequencefadiabaticheating haracterizeds heproduct of the strain and the strain (or cyclicstress)rate.For metals and plastics, atigue failure or corre-spondingly atigue ife can be characterized y cyclicsiress mplitude S or oo: (6m* - o^in)/2versus um-

ber of cycles o failure (N or N1),commonlycalledSNcurves.Figrrt" 32 illustratesseveral xamples f thesecurves. t ian be noted in Fig' 32a that for the steelcurve, there is a limiting minimum stressamplitudebelorvwhichtherewil lbenofai lure.Thisis i l lustratedby thedotted ineand s sometimesalled he atigueoreircluranceinit (o6). Both thecriticalstress mplitudeand the fatigue imit are alteredby the magnitudeofmean stress o-.un (o-u* * o^i)/2)'A simplerela-tionship s oftenused o relate he stress mplitude'on'

s6 lthe meanstress, -.un,and the fatigue imit (or criticalfatiguestress mPlitude, sul:

oa: ofat(l - o^" nf UTS) ( l 1)whereUTS is the ultimatetensilestrength or stress)'Fatigue fracture of both metals and polymers softencharacterized y striationsor so-called lamshellmarkings on a cleanfracture surface'The spacingsofthesesiriations reflect the random application of thecyclicstresshat causes low fatiguecrackgrowth, andbecomevery small for low stressor high cycle(higherfrequency) atigue. Figure 33 illustratesthese eaturesfor-metai fatigue fracture surfacesobserved n thescanning lectronmicroscoPe.6.4.3 Corrosionantl Wear PhenomenaCorrosionandwearof metalsandalloys nvolvemate-rial deteriorationor degradationby chemicaland phy-sical attack respectively.Corrosion and wear are alsointeractive, hai is corrosivewear involving the simul-taneouseffectsof both chemicalattack and physicalremoval of surface material may also occur'Electrochemicalttack nvolvingelectronlow throughcharacteristicanodic and cathodic cells or volumeelementson the metal surface s the most generalmechanism riving corrosionphenomena: xidation-reductionhalf-cell eactions. inc dissolutionn acid sa prime example:

Zn*lHCl -->ZnCl2* Hz t (12)or

Zn *H+ '- Znz+ Hz t (13)or

Zn--> Znz+*28 (oxidationhalf cell reaction)

2H+ + 2E --+H2 f (reductionhalf-cell eaction)+ cathodic eaction ( l 5)

rvhereE represents n electron.Table I lists he so-called lectromotiveeries r thestandardhalf-cellpotentials or someselectedmetalsreferencedo hydrogen standardhydrogenelectrode)Metals lvhich are more reactive han hydrogen areassigned egativepotentialsand are consideredo beanodic o hydrogen,.e.,M -+ Mn++ nE (metaloxidized o ion) (16)


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562Mur

$F aoN ' =8 FE 9r - 3isl ca l' EIr bt . 8r o ^I E v iI 9 eE G ; O| 3 el q aI s EI e ' :I H cI , ! r :I s . *I : . 5I & el ( d =I . E El : eF 3

o i i 9o o EE HF ^x 9F ' t-U >E Fp E

= !d odi v)o oo =! U6 @ g7 ao . =3 eF E5 &i i og 69 =a a

9 ao t 9E aE O9 AE 9. h 6Ec.) co OL !.9put r E5 s3 3 " " i3 F F ; F

lu tuJ c cF < f^ o u Jt r f E


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563IndustrialMaterialsTable 1 StandardSeries) t 25"C

Electrode Potentials (Electromotive

ElementElectrodepotential [in voltsversus he standardhYdrogen

electrodeSHE)IAuPtAgHgCu

(Lesscorrosive)CathodictI

Anodic(More corrosive)

+ 1.498+ 1.200+0.799+ 0.788+ 0.3370.000-0.126-0.136-0.250-0.277-0.403-0.440

-0.744-0.763-1.662-2.363

H2PbSnNiCoCdFeCrZnAIMg

Figure32 Stressamplitude (S) versusnumbet of cycles ofailure (nD for some common metals (a) and plastics(b)'(After Refs7-9.)

Figure33 SEMfractographshorvingatigue triations nthi fracture urfaceor coppera)anda stainless-steelcrew(b).The stainless-steelcrew urface lsoshowsntermixedductileeaturessaconsequencef failuren aprostheticegbone mplant.This rePresentselativelyow cycle atigue(FromRel.6)

2H+ + 2E -->H2 (hydrogen ons reducedohydrogengas) (17)Correspondingly,metalswhich are less eactive hanhydrogin are ssignedpositivepotentialsand arecon-sidered o be cathodic o hydrogen, 'e',

M'+ + n6+ M (metal ons reduced o atoms)(l 8)H, - > 2]H++ 2E (hydrogengas oxidized o

hydrogen ons) (19)As a consequence f thesepotentialdifferences'tcanbe observedn Table 1 that if two dissimilarmetalare coupledelectricallyor immersedn an electrolytthe moie negativemeial halt-cell eactionwill be oxi-dized, rvhile the more electropositivemetal will bereduced,and the overall electrochemicalotential ort h e c e l l r v i l l b e t h e s u m o f t h e h a l f - c e l l p o t e n t igalvanic ell of Zn (-0-763 V) -an! Cu.(+0'337 V)wiU producean overallpotentialof - l ' l V (becau

II5


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564the Cu half_celleduction equiresa signchange,.e.,0.7634.337). T .u gfuuni"'.r*,]'j the electrodehich is oxidized.is,.'tril;;iy-,"#unoo" while theeducedelectroderhsp;;;; ii g:T'J"?:*ll?,h:?:x?;,"-,or exampre,un.b. rlir;';;?;Juli.n,u, wayso:]jfi", or.deposit.moreelecrr"p;;i;; metarsromonrc oturions,r to.protect ;;;;;i asanothersacrificed.or exampli*pp.;; f;;iol." "r""troport_ive than merals suchas il --';; aluminum.onsequently,coDpern ,otutiorr.JittaJiositon FeorI: aurodepositionro'. io uioui'ibiil ,n,, process,attedemen unon.: | 1l:"q r;:;"; i;:,. "ac copperom coppersulfaiesolutions" _i'"y *ining opera_ionsn theUnited tates.ince ilrn?ri*,ras an ntrin_ic,andvery enacious,hin".id;;;l;;;rface, copperutfateotutionsequT: ;;l] "#ntt"nto.ia. ion- 75ppm) o reaciw_ith,t;;i;;Jia ""por" tr,"luminumsurfaceor autodepositionoi-"opp", frornotution. hecoating fsteelil;;ffi;nc to producealvanizedsteelsanotherrnrn"rt "_"."f".Corrosion ontrol..unui*'uJ.alfril;a by similarethods alled athoatcrotirtiori"i"r" .,"",.onsareuppliedo a metal tructureo U. ror".t'ed:galvanicouplingwith a moreanodic ","f i.". _ore anodicjl1 15 "1. bejns r,ote.cted.ndergroundsreelanksnd especiallyuried. ipeliner."ii-"*'""thodicallyprotectedby connectingthem" " ,*rii"iar anode::1:_or,.magnesil$ol "Ir.;" ll.. rabre ).orrespondingly,tanks and pipes "un'riro be con_ected o a d.c. source.throu;d"";;;; to form aimple circuit where:i:d,,.;;;'; 1;!e:"T,lT':;iiJJ:'"#linvolveo-callednodic rotectionh"r" passiveilmsre ormedon metals i "_r;;iir'r_orJ*ro anodicurrents.Corrosioncontrol .un ui.o-t-, -uiti.u.o uyH::T coa^tings,uch s paintso. pturii"i'of course.rowever,f these rackor p."r,-trri'!*ilr"o ,urru..ay hencorrode.The electrochemicaldifferences haracteristicofoupledmetals s also- featureoi "r.i^.ore funda_ff:;"t"f'H::,:::,t" tocattoictri"-.i'1"11"" h"s.

:*uTpl.",p,""ipii*r'l'it;fl:"T1,"","#oo?':::fi,1";r depletionof selectivebrn;;tr';;' J, n"u, g.uinoundariescan producefo"utunoai"7"uiroo,"coupleshich promote acceleratedorrosion-r"uJiio.r,1r"r",::":1r^_rl, f1 examl-I1).n addition,i?""r.uttonoreactronproductswithin a corrodini uni s.pu.utingrain bou-ndarycan createenormotis stresseswhichan accelerate boundary r"pu*iorr. "iirur" 34llustratesan exampleof u ,.tu6O-""rr".f", phenom_

Muenon called exfotiation corrosion,very common inarretyof rolled l-ur,:y_ "]oy, *f,.r," veryelongaterainsoccur n the rolling-dir"lri"".-ii.ilar phenomnacanoccur n ,....::i"l ,t "n 6"nrifjr,r.rr., applieo a corroding systemu"""t"rut" "rick advanceorrackopening, hereby"":.1..;;;; ir,l,"orrorton pro_essoverall.This latter ph"no_"o-on i-s eferred o astre-ssorrosio,nrackingfsCCj.'-"".. ,"Deformation"an ofien ..ihun"" corrosion n genllit. f* gxamfl;, sensitization"r U."," boundariean oftenbe accella,t"aUy str.rJgo?.ltruinl becausislocations rodrair,,in"i #,lii,i:: :il,HHT;ff: :t,lqir: 2l illustratesrris ,*d;,ff. rhis is anmportant issue because-rnu"uf""tir"O productswhich retain a large amount of stored energy,eventainless teel,may-be h, _;.;;;i."io .orrorion inomeenvironments.than.simita.proAu"is,rfri"t t uueeenannealedor otherwi." ,."u,Jili*."*u". disloca_iondensity,rc.welded "r.ri"i, Lri"il o. proneoarious orrosiont.no_.iu-ffiff of stoichioeficvariationsn the reat-ad"d ;;;".of coursehen xide t.;;;;;.'r?rrorion p.o_ucts on a material.uriir"" "r"'^"."0.0 away oremovedby mechanical ontaci- iirr-ir. surface,here s an accelerationr-ii.'"orr#oo reactions.tr::';:,:,:{:xi'#;,"i:::"1':',v,i"*,-,,"o-15;:;;;iffi:":;#:':",'"'"J"fflt'**"ilrpes ransportingslurries, tc.ln addition,erosivewea-r ithout corrosion analsoompromisemateriat performanc" ;i;;; with otheraterial surface removal ifrr""gfr-'rffif ng contactear. wear in a general nr. u"iou.,"ts;, an enor_,uH::Ti":#riil'g,l"ffii:$:l;mj:ncludingoxidation]ur.""l1r-;;'l""ri materialsearsoftermaterials, na of courr" r"ilril"r,s separ_tlngsurfaces ill retardcontact "u.'ft "norn.nu.The.appticatinof very r"rd ;;;;s; il', Ji,.. materi_ls, salsooftenutilizedo ,"turJ-ri.;;* andTiCputter-depositedcoatingso cyrinder*wutt,no ott..ngine artss a typical *u_pi". ---^ "-^:"6.5 CLOSUREMaterialsscience nd engineerings concernedwithhe.searchfor basic-materialsknowledgeand itspplicationin rheprodrrc,i* oi ";;;;; productsand manufacturedsoods. Th; thr";;; types ofa erias-me tals a id uttoyr, f u, i'"-r-poiy*.rr), una


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IndustrialMaterials

Figure34 Exampleof exfoliation orrosion n a 2024 luminumalloy sheet ample rom a section f a KC-I35 air cargoplanebody skin. (a) Optical microscopemageof sectionshouingelongated rain structureand the intergranular orrosionwhichcharacterizeshis phenomenon.b) Scanning lectronmicroscopemage. Photographsourtesy f Maria Posada,UTEP.)

!0 5

ceramicshave been the thrust of this brief overvierv,whilecomposites nd other materials ssues avebeendiscussed riefly. Lacking from this overview havebeen opics involving magneticmaterials-ferromag-netism, paramagnetism, tc., elaboration of opticalproperties f materials,and electronicmaterials, arti-cularly detailsrelating to deviceor integratedcircuitfabrication.Moreover, this introduction to materialsscience nd engineering as ncludedvariationsoffun-damentalssues hich were hought o be more mpor-tant in an industrialor manufacturing ontext han na broadermaterials ontext.While detailedmaterialsselection trategies nd materialsdesigncriteriahavenot beencovered n any specific vay, t is hoped hatthis presentationwill have provided sufticientsub-stance o guide he industrialor manulacturing ngi-neer toward appropriate selections nd adequate

understandingof contemporaryand new materials.In addition, it is hoped that the presentationhasevoked some sensitivitiesof the interrelationshipsbetrveenmaterials,manulacturing strategies, nergyrequirements,nd environmentalssues ither elatingto the materials hemselves,r the consequencesftheir manufacture.The readermight testhis or her basicappreciationof the role that materials cience nd engineering layin the industrialcontextby referring n retrospect ndin srrmmary o Figs. 2 and 5. While at the risk ofsounding fictitious, these tlvo schematics epresentthe essenceof the structure-properties-processing-performance "tetrahedron" which broadly charac-terizesmaterialsscience nd engineering his modelcan be applied to essentially all manufacturedmaterials omponentsnd products.


38/38

566The Further Reading ist will provide someaddi_tional insight nto areasdescribedn this ctrapter nAin the pursuit of more specificmateriaisssueswhichhavenot beenaddressed.he *"d;;i;;r"ouraged toperuse hese ecommendedreadings h.." n.a.rru.yand appropriate.

ACKNOWLEDGMENTThis work was supported by a Mr. and Mrs.Maclntosh Murchiion enAor""J Ci"i. at TheUniversityof Texasat EI paso.REFBRENCESl. J Marin. MechanicalBehaviourof EngineeringMaterials.Newyork: prentice_Hall, iDi), p Z+.2. LE Murr, CS Hiou, S pappu, frl Euu, and SA^ Qninones.hysicaStatus olidi1u1,iz,iS, tols.3. LE Murr.Interfacialt.no_.oa ii M;;"i; andAltoys.Reading, A: Addison_Wesley,g7l.4. MetalsHandbook.qlh ed.uol-t. Vfut..lals ark,OH:ASM International,973.5. LE Murr. Solid_Statelectronics.ew york: MarcelDekker, 97g.6. LE Murr. WhatEveryEngineer hould norvAbout:Material ndComoonentailure,aituieenalysis nd_ Litigation. ewyork: M"r".l;;ld;b;.7. HW Hayden,WG Moffatuof *oln'lnlif,. sr*.tur.andPropertiesf Materials,ol III. N.* Vorf,,Wit.y,1965, 15.8. P-Beardmore,Rabinowit. -freatMaterSciTechnol :267, 975.9. MN Riddell,Gp Koo,andJL O,Toole.olymerEngngSci6,363, 966.

FURTHER READINGBarsoumMW. Fundamentalsf Ceramics. ew york:McGraw-Hill, 997.

BerkowitzAE, Kneller E, eds.Magnetism nd Metalluol. New york: Academicpresi, 1969.Ceramics and Glasses, vol 4. Engineered Mateiliilr""u. Materialsark,oH: .isni lnt..nuCly]u KK- CompositeMaterials.New york: SpriVerlag, 9g7.CourtneyTH. MechanicalBehaviorof Materials.NewyMcGraw-Hill, 1990.Deboo GJ, Burrows CH. Integrated CircuitsSemiconductorDevices:Theory u'nOappfi."tions.ed. New york: McGraw_Hill, 9ll. --rrFontana MG. Corrosio" fogin."ring. :ra ed. New yoMcGraw-Hill, 1996.Hatfield MH, Miller. JH- High Temperature Su;;S.r.,trt Materiats. New york:

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Industrial Materials Science and Engineering