although sotne lact()rs havu t l o t beeu con- sidered. Rcquirelnents \yore sho\'~n to be mcorporaiion of simuhmon techniques

into the r:mtilw ol design and develop-

inent a l ]d eLlsC t)f tlSl2 illpUt of data and

integration with press set up and control.

Numerical prediction of cracks in PM parts l.C.Cante, I.Oliver. (Technical University of Catalonia, Barcelona, Spain.) t:apability of a mnncrical simulation pro-

ccdure to predict crack formation in PM

par t s \va~ demonstrated. 1,1sc was made of

a Pow(:om program and experimental

results, The program incorporates finite

element smmlati(m codes based on large

plastic det;:wntation theory Reference parts

were simuiatcd and parts produced with 'L'

shapcd designs, to provoke cracking.

Modelling of spring-back in green compacts I.M.Prado et al. (Polytechnic University of Cataluna, Barcelona, Spain.) Elastic bchaviour of green dic' conlpactcd

samples was investigated using uniaxial

c()nlprcss ion tests ()n pr i s lna t ic specimens.

Linh)admg and i-cloadmg cvcles rcvealed

mm-l incai tx and anisotropy of elastic

responses. A model describing mechanical

behaviour in ter lns Of strain tensor was

proposed. ~.\ strtlcttn'al tensor was used to

accotnl t t:or [ r a n s \ e r s c a n i s o t r o p y during

compaction. Parantctcrs for the model

x~erc determined cxperimentall):

Advances in finite element modelling l.Oliver et al. (Technical University of Catalonia, Barcelona, Spain.) It was reported that a new, finite elcment

bascd nlethodology had been developed

fi~l" powder transfer, compaction and ejec-

ti(m of a PM part. A l)owCont program,

based on large plastic deformation, con-

tact-friction algorithms xxith remeshing

strategies to avoid distortion of finite ele-

ment nlesh was used. A user-friendly con>

putcr was used for data input and visuali-

sation of results. Details of the continuum

mechanics, development of the finite ele-

ment model and practical applications

were presented.

Numerical analysis and prediction of defects in die compaction M.Shtern, O.Mikhailov. (Inst. for Problems of Materials Science, Kiev, Ukraine.)

Die compaction was analysed with regard

to dcnsit~ variation. A modified model,

sensitive to density and eccentricity of

plastic potential was proposed. A finite

element version allows avoidance of

refreshing of the" mesh. Pressing diagrams

were examined and density distribution

defined. The significance of shear strain

rates for formation of cracks was noted.

High-density processing Green turning of warm compacted PM steels A.Benner, P.Beiss. (Aachen University of Technology, Aachen, Germany.) It was noted that there had been Little

study of machining of green warm com-

pacted PM parts. Two warm compacted

stccls were machmcd in thc green state.

Criteria for satisfactory machining were

shown to be surface quality and edge

integrity The object of the investigation

was to optimise the cutting process by

study of effects of process and tool

parametcrs.

Laboratory processing of steels to high density A.S.Wronski et al. (University of Bradford, Bradford, UK.) Means to incrcasc smtercd density of PM

steels were hwestigated. Compaction pres-

sures were 600MPa to 800MPa. One strat-

egy was warm compaction, sintering, slow

co(fling through the ferrite transition range

and cold repressing. The other was to add

B to promote liquid phase smtering. Cold

rcsizmg raised density to 7.6gm/cm 4. 0.1

to 0.4%B gave densities up to 7.Sgm/cm -3.

More than 0.4%B rcsuhed in formation of

brittle intergranular fihns. Mechanical

properties were described.

Influence of microstructure on fracture toughness of cold work tool steels W.Liebfahrt et al. (BOhler Edelstah[ GmbH, Kapfenberg, Austria.) Structure and mechanical properties of

cold work tool steels were discussed.

Structures of hard carbide particles in a

martensitic matrix confer hardness and

wear resistance and should have adequate

fracture toughness. Increase in carbide con-

tent increases hardness and wear resistance

but reduces toughness. Plane strain fracture

toughness was investigated with regard to

carbide particle content, size and distribu-

tion using quantitative scanning electron

microscopy. Sizes of crack tip plastic zones

were calculated and compared with car-

bide interparticle separation. Composition

was less critical than carbide particle

characteristics.

Effect of niobium on structure and properties of PM high-speed steels H.Chung et al. (Ajou University, Gyunggi, Korea.) It was noted that PM high-speed steels

could be made with higher %Nb than

cast/wrought alloys. F.ffects of 0 to

5wt%Nb on structure and properties of

PM high-speed steels were investigated.

Highest Rockwell hardness attained was

66C at l%Nb. Bcnd strength decreased

with increased %Nb. Hardness, wear

resistancc and resistance to thermal soft-

ening at 600"C was greater than fi,r steels

without Nb.

Impact resistance and properties of PM high-density stainless steel G.L.Garagnani, M.Rosso. (Polytecnico of Torino, Torino, Italy.) Porosity was shown to impose a limita-

tion to good propertics in sintcred mate-

rials. Means of reducing porosity were

identified. A novel method involving reac-

tive sintering of stainless steel was pre-

sented. Studics to optintise processing to

cause reactive sintermg were described.

Pressing was at 500MPa or 7f)0MPa.

Sintering was either, I hour at l I g0"(] in

pure H, 1 hour in vacuum at 1250"C or 30

minutes at less than 1275<'(i in a pusher

furnace in N-50%H. Samples with

increased density and rcsistancc proper-

ties were obtained.

Isostatic pressing A high-pressure cell for isostatic pressing of ceramic powders C.S.Dumitru et al. (University of Craiova, Craiova, Romania.) Aspects of high pressures, experimental

problems and industrial practice of isosta-

tic pressing were reviewed. A high-pressure

cell fnr isostatic pressing was described.

Working method, performance and test

results were presented. Solutions were

given for industrial exploitation.

Rapid tooting and prototyplng Advances in materials for direct metal laser sintering F.Petzold et aL (Fraunhofer Inst., IFAM.,Bremen, Germany.)

metal-powder.net February 2003 ~ 37

it was reported that an improved metal

powder had been developed for direct metal

laser cintering. The powder is a blend

designed to decrease surface tension of the

melt during laser irradiation, optimise vis-

coslty of the melt, reduce the melting point

of the powder and improve properties of

the sintered part. Structures and properties

of the laser-sinrered alloys were presented.

PM prototype component

manufacture by direct metal

laser sintering

J.Kotila et al. (Electra Optical Systems

Finland, Rusko, Finland.)

New steel and bronze, non-shrinking,

po\vders for direct metal laser sintering

were described. These could be used ro

make true net-shape parts in a single stage

by ube of high-power computer controlled

lascm to \lntcr rhe powders, layer-by-layer.

Clo5c dimensional tolerances, fO.OSOmm,

.Ind dcrnil tolerance, 20mm, could be eco-

nomically attained.

Features of three-dimensional printing

of metal powders

F.Petzold et al. (Fraunhofer Inst.,

IFAM.,Bremen, Germany.)

A novel technique for rapid prototyping and

tooling, three-dimensional printing, was

descrl bed. Computer-controlled

print heads apply liquid binder to a

stationary powder hed through nozzles

building up layer-by-layer, to fabricate a

green part. The green part is debound

and sintcred. The method has potential

for production of high performance

part\. Properties of 3161. stainless

srccl .~nd a bronze were given. An applica-

tion, production of tooling for plastic injec-

tlon moulding machines, was described.

Dependence of densities and contours

on layer thickness during sintering of

iron powder

R.Karlsen. (Norwegian University of

Science and technology, Trondheim,

Norway.)

Durtng conaolldation, of metal powders,

in the metal printing process thin layers of

Ioo\c powder are progressively builr up

in10 enplneering parts by passage of elec-

tric currem. Energy developed is related to

IIIC rcsI\tdncc of the powder and the layer

thickness. An in\,estlpation of the effects of

IJ!CT rhickws, 011 mucture and contours

111 utllplc\ m:tdc from differenr powders

I\‘., \ clc\cri hcd.

Self-pro ! tempera

agating high- ure synthesis

Production of composite powders by

self-propagating high-temperature syn-

thesis

T.L.Talako et al. (Powder Metallurgy

Research Inst., Minsk, Belarus.)

Investigations of synthesis of double

(Cr,Ti) carbides, by self propagating high

temperature synthesis were described. The

object of adding Cr was to increase oxida-

tion resistance. Materials with fine struc-

tures were obtained which were deposited

011 substrates, with good adhesion

attained. The coated materials had long

service lives.

Production of iron aluminide powder by

self propagating high temperature

synthesis

T.L.Talako et al. (Powder Metallurgy

Research Inst., Minsk, Belarus.)

Properties of Fc aluminides were dis-

cussed. It was shown that FeAl has good

resistance to wear and oxidation but that

rhere is a risk of cmbrittlement by N.

Samples of E‘eAI were produced by self

propagating high temperature synthesis at

compositions which allowed Fe2AI,5 and

PeAI, to form. These were reported to

reduce cracking.

Metal matrix composites and dis ersion- strengt R ened materials Requirements for electronics packaging

G.Lefranc et al. (Siemens AG, Miinchen,

Germany.)

Requirements, thermal conductivity, ther-

mal expansion and mechanical properties,

of materials used in electronics packaging

were reviewed. Thermal fatigue was identi-

fied as a cause of failure. Development of

Cu-SiC composites was described. Cu-(40

to i’O)vol”/oSiC composites were prepared

by PM methods. Cu-Sic has high thermal

conductivity, due to the Cu, and low ther-

mal expansion and high elastic modulus,

due tn the SiC. Ti was added to improve

bond strength between Cu matrix and Sic.

Properties were discussed.

Development of copper-based metal

matrix composites for electric motor

commutator rings

S.A. El-Badry et al. (AIAzhur University,

Cairo, Egypt.)

It was reported that Cu-based metal

matrix composites had been developed for

DC motor commutator rings, to reduce

wear on the part. Ring samples were made

by PM methods with different types and

amounts of hard particles and solid lubri-

cants. Wear characteristics were deter-

mined on a friction test rig that could be

used with or without electric current. Best

commutator performance was found for

Cu-I % graphite. Wear properties were

better when hard particles had been added

to the composite.

Thermodynamics of in situ processing of

metal matrix composites

R.Orban. (University of Cluj-N apoca,

Cluj-Napoca, Romania.)

Thermodynamics of in situ processing of

metal matrix, Fe, Cu, Al and Ti, with

oxide, nitride, carbide and boride rein-

forcements were investigated. It was

deduced that compositional design was

feasible. PM processing variants, taking

process and material parameters into

account, were discussed.

Surface treatments and coatings Preparation and characterisation of

nano-scale multi-layered ceramic

structures

T.Kimura et al. (Ryukoku University, Seta,

Otsu, Japan.)

Polycrystalline multi-layered films of TiN-

ZrN, TiN-CrN and TiN-SiN were

deposited on glass substrates by dual ion

beam sputtering. The properties and crys-

tallographic relationships were investigat-

ed. Superlattice structures were detected.

Th ere was enhancement in hardness at

film thicknesses of 15 to 20nm.

Mechanisms were discussed in terms of

free energies of nitride formation and

residual stresses.

Hypervelocity powder deposition by flux

compression devices

M.D .Driga et al. (University of Texas at

Austin, Austin, USA.)

A method for deposition of powders at

very high velocities was described. This

uses a military railgun as the drive for

powder and flux compression rotating

electromagnetic converters. Powder

velocity was shown to be more than dou-

ble that attained in conventional thermal

spray techniques. Mean power was said

to be 25OkW with 80,OOOkW peaks. A

fusion bond with the substrate was

dcmonstratcd.

38 AP February 2003 metal-powder.net