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622 MRS BULLETIN/SEPTEMBER 2003

This year marks the centennial of theWright brothers’ first flight. In the secondhalf of the last century, aircraft poweredby jet engines came to dominate bothcivilian and military flights, and they con-tinue to have tremendous impact on theeconomy and on our lives (e.g., aircraftturbine engines are the single largest U.S.export product).

The history of the jet engine goes backmuch farther than one would suppose.Jacques Etienne Montgolfier was the firstto propose reaction propulsion for aircraftin 1783. His concept was intended for aballoon rather than an airplane and morefor steering than main propulsion. The firstpatent for a turbine engine appeared in1791; it was intended for use on a horselesscarriage (automobile). Charles de Leuvriéfirst suggested the idea for a jet-poweredmonoplane in 1865, but it was not until1928 that Frank Whittle, a 21-year-oldRoyal Air Force cadet, advanced the ideaof jet propulsion for aircraft in a publishedthesis. Although his concept was rejectedby the authorities of the time, he perse-vered and by April 12, 1937, had built and

successfully tested his first turbo-jet en-gine. Whittle’s engine first powered anairplane (the Gloster E2) on May 15, 1941.Meanwhile, an independent parallel effortwas going forward in Germany. Hans vonOhain obtained a patent for a jet engine onNovember 10, 1935. With backing fromErnst Heinkel, he built the He S3B engine,which successfully powered an airplane,the He 178, on August 27, 1939. Both ofthese developments came too late to havea significant impact on World War II, al-though some military jets were flown inthe 1940s. The commercial significance ofthe new mode of power was apparent,and in 1952, the British Overseas AirwaysCo. (BOAC) inaugurated the first sched-uled jet passenger service. In 1992, Ohainand Whittle shared the Draper Prize for“early jet development and contributionsto mankind.” Readers may be interestedin their biographies1,2 and in anotherbook3 that clearly explains the fundamen-tals of a jet engine.

The need in any engine for materialswith strength at high temperatures wasrecognized early, but the first step was to

use alloys already known for their modesthigh-temperature strength and oxidationresistance, such as the Ni-Cr alloys intro-duced by Marsh in 1906. Only in the late1930s and early 1940s, with the introduc-tion of the jet engine, was a concerted re-search effort launched, principally by theMond Nickel Co. in the United Kingdom,to develop alloys particularly for this pur-pose. The history of this development wassketched in a recent review.4 Present-dayalloys for this application, Ni-based super-alloys, evolved during a period of 70 yearsor more through small incremental changescontributed by engine manufacturers, ma-terials producers, and materials researchand development specialists. These alloysare composed of Ni3Al (�´) precipitates ina Ni (�) matrix with admixtures of 10–12other elements dissolved in one or both ofthe major phases. The current alloys oper-ate for thousands of hours under loads onthe order of 140 MPa at 85% of their meltingpoint. It is now clear that neither the in-creasing sophistication of our understand-ing of how such performance is achieved,nor the possibility of further tinkering withcomposition or processing, nor advancesin turbine design (e.g., more complexcooling systems) will yield the improve-ments demanded by engine designers. Westill need substantially improved high-temperature materials that can only comefrom a completely different materials class.

The jet engine is a very complex yet op-erationally simple device. Figure 1 showsa GE 90-115B engine, the most powerfuljet engine in the world. It consists essen-tially of a stationary, hour-glass-shaped,cylindrical case on which all of the vanes(nozzles) and the combustion chamber(combustor) are attached, and a rotatingmandrel on which a series of disks (rotors,wheels) are mounted. Attached to the pe-ripheries (perimeters/rims) of the disksare the blades (either compressor bladesor turbine blades). The vanes duct the airinto appropriate directions to effectivelypropel the blades. Alternating rows ofvanes and blades are arranged in both thecompressor and turbine sections. As theair is compressed, its temperature rises; itis then mixed with fuel and burned in thecombustor to raise the temperature. Thehigh-temperature, high-pressure (high-energy) gas coming out of the combustoris ducted by the first-stage, high-pressureturbine (HPT) vanes to propel the first-stage HPT blades. The efficiency and per-formance of the jet engine are stronglydependent on the highest temperature inthe engine—the inlet temperature of theHPT—and it is the high-temperature ca-pability of these parts that is critical. Toachieve higher thrust, higher operating

Ultrahigh-TemperatureMaterials for JetEngines

J.-C. Zhao and J.H.Westbrook, Guest Editors

AbstractThis introductory article provides the background for the September 2003 issue of MRS

Bulletin on Ultrahigh-Temperature Materials for Jet Engines. It covers the need for these ma-terials, the history of their development, and current challenges driving continued researchand development.The individual articles that follow review achievements in four different ma-terial classes (three in situ composites—based on molybdenum silicide, niobium silicide, andsilicon carbide, respectively—and high-melting-point platinum-group-metal alloys), as well asadvances in coating systems developed both for oxidation protection and as thermal barriers.The articles serve as a benchmark to illustrate the progress made to date and the challengesahead for ultrahigh-temperature jet-engine materials.

Keywords: coatings, composites, ductility, jet engines, oxidation, oxides, platinum-group-metal alloys (PGM alloys), silicides, strength, structural materials, thermal-barriercoatings, toughness, ultrahigh-temperature materials.

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MRS BULLETIN/SEPTEMBER 2003 623

temperatures must be realized. To achievehigher efficiency, engines must be madesignificantly lighter without loss of thrust.In either case, it is obvious that completelynew families of materials must be devel-oped, ones with higher melting points andgreater intrinsic strength.

There are only four categories of ma-terials that can be considered: refractorymetals, monolithic ceramics, intermetalliccompounds, and composites (natural orsynthetic).

The first category can be immediatelyruled out. None of the refractory metals issufficiently oxidation-resistant, and all ofthem, with the exception of chromium, aresubstantially denser than present-day Ni-based alloys. Chromium, while having theadvantage of a lower density than nickel,is only marginally tough at room tempera-ture and is subject to nitrogen embrittlementwhen exposed to air at high temperatures.Klopp5 and Ro et al.6 summarized the progress made with Cr-based alloys; these

alloys are currently not considered goodprospects for meeting the need. Perhapssignificantly, Cr-based alloys were not cov-ered in Sims et al.’s 1987 work, Superalloys II.7

Many monolithic ceramic materialspossess good strength at jet-engine oper-ating temperatures. However, their inher-ent brittleness poses a significant challengein withstanding the rigors of assembly andthe impact damage caused by foreign ob-jects that may pass through the engines inoperation. These materials will have limitedapplications in turbine engines withoutfurther development of improved mate-rials and innovative system architectures.

Thus, we focus on the remaining twoclasses of potential materials: intermetalliccompounds and composites. It is thesetwo groups that are the subjects of the de-tailed reviews that follow in this issue ofMRS Bulletin.

There are three families among the in-termetallics that have received serious at-tention for jet-engine applications: �-TiAl,NiAl, and the platinum-group metal (PGM)compounds. TiAl is considered from anengineering point of view to be the mostmature intermetallic for jet-engine appli-cations. Yet its modest melting point(�1500�C) precludes it from use in high-temperature blades and restricts it to thelow-pressure turbine and static parts ofthe engine. After more than 20 years of ef-fort on TiAl,8–11 it is not yet used in com-mercial jet engines, despite the fact that a1993 engine test of a low-pressure fan with98 TiAl blades was successful. The prob-lems that remain include low room-temperature ductility (1–2%), low fracturetoughness, high stress-sensitivity of fa-tigue life, and high manufacturing cost forfinished parts.

NiAl has a number of attractive proper-ties for jet-engine applications, such as ahigh melting point (�1650�C), good thermalconductivity, low density, and intrinsic oxi-dation resistance. With suitable alloying(Ta � Cr), good strength properties at tem-peratures higher than 1000�C can beachieved. Alloy parts based on this inter-metallic have been successfully made by avariety of processes (e.g., investment cast-ing, powder metallurgy, hot extrusion,and injection molding). Tests for applica-tion as static parts for stationary turbineshave been successful. In NiAl alloy devel-opment for jet-engine applications, bothdirectionally solidified eutectics and poly-crystalline multiphase structures havebeen explored. Serious consideration forengine applications will require bettertoughness at room temperature and highercreep strength at high temperatures. Re-cent summaries of the status of NiAl forengine applications may be found in Mir-

Ultrahigh-Temperature Materials for Jet Engines

Figure 1. (a), (b) Photographs of a high-pressure turbine (HPT) vane and a HPT blade of ajet engine. (c) Schematic arrangement of the stationary vanes relative to the rotating bladeswithin the engine. (d) Illustration of the GE 90-115B jet engine, showing its variouscomponents. (e) Pressure and temperature trends from the front to the back of the engine.






acle and Darolia,12 Noebe and Walston,13

and several other papers.14–17

The PGM-based intermetallic alloysthat have been studied for possible appli-cation as high-temperature structural ma-terials fall into two classes: those that areisomorphous with Ni3Al (e.g., Pt3Al), andthose that are isomorphous with NiAl (e.g.,RuAl). In both cases, the advantages ofPGM-based intermetallics over Ni-basedsuperalloys are a significantly higher melt-ing point (�1500�C for Pt3Al and �2100�Cfor RuAl) and inherent oxidation resis-tance, albeit with some increase in density.Recent reviews of these alloys are pre-sented by Wolff et al.18,19 and Yamabe-Mitarai et al.20 Most of the attention hasbeen focused on Pt- and Ru-based com-pounds, but there have been some studiesof Ir-based21 and Rh-based22 materials.Progress toward the desired properties hasbeen either by alloying to improve strengthand reduce density or by oxide-dispersionstrengthening (ODS). In this issue, Cornishet al. review current activities and achieve-ments with each approach.

Composite materials are defined23 as amacroscopic combination of two or moredistinct materials having a recognizableinterface between them. More particularly,structural composites are those in which acontinuous matrix phase bonds and pro-vides toughening characteristics to an arrayof pieces of a stronger, stiffer reinforcementphase. Structural composites may be formedby artificially bringing together a suitablecombination of matrix and reinforcementphase (as in the case of glass-fiber-reinforced polymers) or produced natu-rally by suitable processing of a carefullyselected composition (so-called in situ com-posites). All three composite systems re-viewed here fall into this category of in situcomposites. All are silicon-rich, which low-ers density and provides a basis for oxida-tion resistance, but they differ in the natureof the reinforcing phase or phases. Dimidukand Perepezko review achievements within situ composites in the Mo-Si-B system,Bewlay et al. address the Nb-Ti-Cr-Si sys-tem, and Naslain and Christin cover SiC/SiC ceramic-matrix composites (CMCs).The oxidation behavior and the density-normalized strength of these materials arecompared in Figures 2 and 3.24–37 Thereader is cautioned that the data for thedifferent materials were not necessarilyobtained under comparable conditionsand that all materials shown are undercontinuous development with progres-sively improving properties.

Although all of the materials discussedin this issue show promise as ultrahigh-temperature materials for advanced jet en-gines, there is no clear winner among them

so far. Relatively speaking, the develop-ment of Mo-Si-B, Nb-silicide-based com-posites, and PGM-based alloys is still in itsinfancy, while the development of CMCshas a much longer history. Each class ofmaterials has its own merits and draw-backs, as briefly summarized here anddiscussed in the respective articles.� SiC/SiC Ceramic-Matrix Compositesare the closest to the long-term engine test-ing stage; several engine tests with CMCsas combustion chambers have been per-formed on land-based gas turbines, andsimilar efforts for jet engines are currentlyunder way. Their strength is relatively low,even on a density-normalized basis. Forwell-designed systems, the good impactresistance and stability at high operatingtemperatures make this system an attrac-tive option; significant design effort willbe required to take full advantage of the

properties as well as to master the chal-lenges poised by mating CMCs withmetallic components. Significant progresshas been made in environmental-barriercoatings to combat the SiO2 evaporationproblem in high-velocity water-vaporenvironments. Cost, reliability, estimationof component life, and the manufacture of complex shapes are among the chal-lenges requiring continued attention anddevelopment.� Nb Silicide Composites show good oxi-dation resistance, good resistance to pesting(intermediate-temperature pulverization),reasonable fracture toughness, good fa-tigue resistance, good high-temperaturestrength, good impact resistance, and canbe cast reasonably well. Good coatingshave also been developed for these com-posites. However, combining high oxida-tion resistance with high strength in a


Figure 2.The oxidation/recession rate of various ultrahigh-temperature materials discussedin this issue of MRS Bulletin. The data were obtained from References 24–29.The bestpublished data were plotted for each class of materials.The recession rate is a good figureof merit for oxidation resistance, as it measures the material loss in thickness by oxidationat certain temperatures and time periods.The material loss is usually by formation andspallation of a thermally grown oxide scale, or by evaporation of the metal and oxide in thecase of platinum-group metal alloys and Mo-Si-B.The results on Mo-Si-B are only for onealloy (Mo-11at.%Si-11at.%B) and are only preliminary, sensitive to a variety of processing,composition, and microstructure variables.The SiC data were used as a proxy forceramic-matrix composites (CMCs), since the CMC data were not available in the literature.The data reported here for SiC were an average of both lean- and rich-burn combustionconditions.28 The oxidation data were not obtained under identical conditions, therefore thisfigure is only intended to show the approximate present performance for each class of ma-terials; such data are likely to get better with further materials development.






single composition remains a problem, asdoes manufacturability.� Mo-Si-B Composites exhibit excellenthigh-temperature creep strength, out-standing high-temperature yield strength,and excellent oxidation resistance at tem-peratures above 1000�C. Among theirproblems are less-than-desirable oxida-tion resistance at intermediate tempera-tures, poor manufacturability, poor fatigueresistance, poor impact resistance, and lowfracture toughness. Improvements on thesefronts are required.� PGM-Based Alloys show excellent oxi-dation resistance with low amounts of al-loying additions. Most of the alloys havelow strengths (both yield and creep rup-ture), very high density, and high cost. TheIr-based alloys show very high strength, butthey no longer have the oxidation resistanceof the PGMs due to high alloying. The de-velopment of PGM-based alloys is still inits infancy, and there is the potential forhigh strength by both alloying and ODS.In order for them to be used in jet engines,innovative designs will be required to takeadvantage of the excellent properties of

PGM-based alloys while avoiding theproblems of high density and cost.

The strength data of Al2O3/GdAlO3 Eu-tectic Composites are shown in Figure 3 asa benchmark of oxide–oxide composites.Initial work on this material29 shows greathigh-temperature strength, reasonable frac-ture toughness (5 MPa m1/2 at room tem-perature and 13 MPa m1/2 at 1600�C)38 andgreat oxidation resistance (no loss of mate-rial even after exposure at 1700�C for 1000h). But it has a serious drawback—a lackof the thermal-shock resistance requiredto survive engine startups and shut-downs. It would be a good potential high-temperature material if the thermal-shock-resistance problem were solved, either byengine design or by material improve-ment. In addition, the high strength of thismaterial only exists in the melt-grown,in situ composite where no glassy phaseexists along interfaces. It would greatlyimprove the manufacturability of this com-posite if formation of the glassy phase dur-ing a sintering process could be avoided,thus making complex, near-net-shapeblades possible.

For a bare material to survive in theoxidative environment of a high-temperature, high-velocity gas streamwithin a HPT, it needs either to form aprotective oxide scale or to be virtuallyinert, as are the precious metals. Two pro-tective oxides, Al2O3 and SiO2, are the bestcandidates as oxide scales. It is this factthat dictated the basic compositions of thecomposite materials reviewed here. SiO2grows much slower than Al2O3 at hightemperatures, thus conferring a clear ad-vantage, but it evaporates more quickly ina high-velocity, moist environment. Com-positional modification of the substratematerials has not yielded an attractivecombination of oxidation resistance andhigh-temperature strength. Thus, it is con-cluded that all prospective new materialsfor jet-engine blades will require coatingsto achieve acceptably long life. These coat-ings are quite complex materials systems.They are designed to serve two main func-tions: oxidation protection and thermalprotection of the substrate material. Otherlayers may be included to provide auxiliaryfunctions: bond coats between coatinglayers or between coating and substrate,or diffusion barriers to prevent degrada-tion of either substrate or coating by in-ward or outward diffusion of components.A series of recent symposia chaired by Da-hotre39 has recorded progress in this area.In the final article in this issue, Nichollsdescribes the current status of the field.

But what is the future? Despite theprogress made in understanding theproblems confronting high-temperaturestructural materials and the ingenious de-velopments in composition selection andprocessing for new base materials, the factremains that none of the systems describedhere is in use in aircraft flying today. Con-tinued developments will probably producesome further property improvements, butwhether they will be enough to instigatewide usage is difficult to say at this point.It is critical to have a combined effort bymaterials people and designers to learn towork with low-ductility materials. On thematerials side, we need materials and proc-ess improvements that will increase theconsistency and reliability of performance,even at low ductility and toughness levels;and on the design side, new concepts mustbe developed that are more forgiving oflower-ductility materials. An alternate routeto success may be to explore completelynew base systems, perhaps ternary orquaternary compounds.

For those who are new to this subjectfield, we provide this list of suggestedreadings. Superalloys are covered in twomonographs, those of Sims et al.7 and ofDonachie and Donachie,40 as well as in the


Figure 3. Comparison of the density-normalized strength of various ultrahigh-temperaturematerials.The data were obtained from References 30–37 and the articles published in thisissue of MRS Bulletin. The best published data for each class of material are plotted here.Some of the strength data are from compression and bending tests.The results on Nbsilicide composites, Mo-Si-B, and CMCs are only preliminary, and the low-temperature dataare mostly elastic-fracture strength, which is very sensitive to defects and microstructure.This figure is intended only to show the best published performance so far for each class ofmaterials. The MASC (metal and silicide composite) alloy has a composition ofNb-25Ti-8Hf-2Cr-2Al-16Si. Nb-Si Alloy C is an alloy patented by General Electric Co. and isdescribed in more detail in the article by Bewlay et al. in this issue. DPH Pt-10Rh is a“dispersion-hardened” (DPH) platinum alloy containing 10 at.% Rh. For more on platinum-group-metal alloys, see the article by Cornish et al. in this issue.






recurring Seven Springs Conferences onSuperalloys volumes.41 Intermetallic com-pounds are treated in monographs bySauthoff42 and by Stoloff and Sikka,43 as wellas in great detail in the three-volume trea-tise edited by Westbrook and Fleischer,44

and in a series of Materials Research Societysymposia proceedings.45 Composites arecovered in considerable detail in the re-cent ASM Handbook, Vol. 21.46 Finally, theInternational Symposium on StructuralIntermetallics series, three of which havebeen published so far,47 considers compos-ites, intermetallics, and other types ofhigh-temperature structural materials.

Background information and tutorials onjet engines and advanced high-temperaturematerials may also be found on the Inter-net. Some of these sites are� Ultra-Efficient Engine Technology(www.ueet.nasa.gov/Engines101.html);� Superalloys: A Primer and History(www.tms.org/Meetings/Specialty/Su-peralloys2000/SuperalloysHistory.html);and� AZoM—Metals, Ceramics, Polymers,Composites, An Engineer’s Resource(www.azom.com).

DisclaimerThe views, opinions, and conclusions

contained in this introductory article arethose of the guest editors for this issue andshould not be interpreted as representingthe official policies, positions, or endorse-ment, either expressed or implied, ofGeneral Electric Co. or of Brookline Tech-nologies, their employers. They alsoshould not be interpreted as representingthe opinions or positions of the other au-thors in this issue of MRS Bulletin or oftheir respective institutions.

AcknowledgmentThe authors are pleased to acknowl-

edge the benefit of critical reviews of adraft of this introduction by the authors ofthe other articles in this issue and by H. Lipsitt.

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Kobayashi, E. Bannai, and H. Harada, ScriptaMater. 46 (2002) p. 331.7. C.T. Sims, N.S. Stoloff, and W.C. Hagel, eds.,Superalloys II (John Wiley & Sons, New York,1987).8. S.-C. Huang and J.C. Chesnutt, in Intermetal-lic Compounds: Principles and Practice, Vol. 2, ed-ited by J.H. Westbrook and R.L. Fleischer (JohnWiley & Sons, New York, 1995) p. 73.9. Y.-W. Kim, R. Wagner, and M. Yamaguchi,eds., Gamma Titanium Aluminides (The Minerals,Metals and Materials Society, Warrendale, PA,1995).10. Y.-W. Kim, D.M. Dimiduk, and M. Loretto,eds., Gamma Titanium Aluminides 1999 (TheMinerals, Metals and Materials Society, Warren-dale, PA, 2000).11. Y.-W. Kim and A.H. Rosenberger, eds.,Gamma Titanium Aluminides 2003 (The Minerals,Metals and Materials Society, Warrendale, PA)in press.12. D.B. Miracle and R. Darolia, in IntermetallicCompounds: Principles and Practice, Vol. 2, editedby J.H. Westbrook and R.L. Fleischer (JohnWiley & Sons, New York, 1995) p. 53.13. R.D. Noebe and W.S. Walston, in StructuralIntermetallics 1997 (ISSI-2), edited by M.V.Nathal, R. Darolia, C.T. Liu, P.L. Martin, D.B.Miracle, R. Wagner, and M. Yamaguchi (TheMinerals, Metals and Materials Society, Warren-dale, PA, 1997) p. 573.14. M. Palm and G. Sauthoff, in Structural Inter-metallics 2001 (ISSI-3), edited by K.J. Hemker,D.M. Dimiduk, H. Clemens, R. Darolia, H. Inui,J.M. Larsen, V.K. Sikka, M. Thomas, and J.D.Whittenberger (The Minerals, Metals and Mate-rials Society, Warrendale, PA, 2002) p. 149.15. W.S. Walston and R. Darolia, in Structural In-termetallics 2001 (ISSI-3), edited by K.J. Hemker,D.M. Dimiduk, H. Clemens, R. Darolia, H. Inui,J.M. Larsen, V.K. Sikka, M. Thomas, and J.D.Whittenberger (The Minerals, Metals and Mate-rials Society, Warrendale, PA, 2002) p. 735.16. J.D. Whittenberger, S.V. Raj, I.E. Locci, andJ.A. Salem, in Structural Intermetallics 2001 (ISSI-3), edited by K.J. Hemker, D.M. Dimiduk,H. Clemens, R. Darolia, H. Inui, J.M. Larsen,V.K. Sikka, M. Thomas, and J.D. Whittenberger(The Minerals, Metals and Materials Society,Warrendale, PA, 2002) p. 775.17. S.V. Raj, I.E. Locci, and J.D. Whittenberger,in Structural Intermetallics 2001 (ISSI-3), editedby K.J. Hemker, D.M. Dimiduk, H. Clemens, R.Darolia, H. Inui, J.M. Larsen, V.K. Sikka, M.Thomas, and J.D. Whittenberger (The Minerals,Metals and Materials Society, Warrendale, PA,2002) p. 785.18. I.M. Wolff, G. Sauthoff, L.A. Cornish, H.DeV. Steyn, and R. Coetzee, in Structural Inter-metallics 1997 (ISSI-2), edited by M.V. Nathal, R.Darolia, C.T. Liu, P.L. Martin, D.B. Miracle, R.Wagner, and M. Yamaguchi (The Minerals,Metals and Materials Society, Warrendale, PA,1997) p. 815.19. I.M. Wolff, in Intermetallic Compounds: Princi-ples and Practice, Vol. 3, edited by J.H. Westbrookand R.L. Fleischer (John Wiley & Sons, NewYork, 2002) p. 53.20. Y. Yamabe-Mitarai, Y. Ro, T. Maruko, T.Yokokawa, and H. Harada, in Structural Inter-metallics 1997 (ISSI-2), edited by M.V. Nathal, R.Darolia, C.T. Liu, P.L. Martin, D.B. Miracle, R.Wagner, and M. Yamaguchi (The Minerals,

Metals and Materials Society, Warrendale, PA,1997) p. 805.21. Y. Yamabe-Mitarai, Y.F. Gu, and H. Harada,Platinum Met. Rev. 46 (2002) p. 74.22. Y. Yamabe-Mitarai, Y. Koizumi, H.Murakami, Y. Ro, T. Maruko, and H. Harada,Scripta Mater. 36 (4) (1997) p. 393.23. D.B. Miracle and S.L. Donaldson, in ASMHandbook Volume 21: Composites, edited by D.B.Miracle and S.L. Donaldson (ASM Interna-tional, Materials Park, OH, 2001) p. 3.24. M.R. Jackson (private communication).25. H.A. Lipsitt, M.J. Blackburn, and D.M.Dimiduk, in Intermetallic Compounds: Principlesand Practice, Vol. 3, edited by J.H. Westbrookand R.L. Fleischer (John Wiley & Sons, NewYork, 2002) p. 471.26. M.G. Mendiratta, P.R. Subramanian, T.A. Parthasarathy, and D.M. Dimiduk, (unpublished).27. Iridium Databook (International Nickel Co.,Mississauga, Ontario, 1960s).28. R.C. Robinson and J.L. Smialek, J. Am.Ceram. Soc. 82 (7) (1999) p. 1817.29. Y. Waku, Adv. Mater. 10 (1998) p. 615.30. G.L. Erickson, JOM 47 (4) (1995) p. 36.31. Y.F. Gu, Y. Yamabe-Mitarai, S. Nakazawa, Y.Ro, and H. Harada, Metall. Mater. Trans. A 33A(2002) p. 1281.32. G.S. Corman, M.K. Brun, and K. Luthra, inProc. ASME Int. Gas Turbine & Aeroengine Con-gress & Exhibition (ASME International, NewYork, 1999) paper No. 99-GT-234.33. G.S. Corman, A.J. Dean, S. Brabetz, M.K. Brun, K.L. Luthra, L. Tognarelli, and M.Pecchioli, Trans. ASME—J. Eng. Gas Turb. Power124 (3) (2002) p. 459.34. K.L. Luthra and G.S. Corman, in High Tem-perature Ceramic Matrix Composites, edited by W.Krenkel, R. Naslain, and H. Schneider (Wiley-VCH, Weinheim, 2001) p. 744.35. P.J. Hill, Y. Yamabe-Mitarai, H. Murakami,L.A. Cornish, M.J. Witcomb, I.M. Wolff, and H.Harada, in Structural Intermetallics 2001 (ISSI-3),edited by K.J. Hemker, D.M. Dimiduk, H.Clemens, R. Darolia, H. Inui, J.M. Larsen, V.K.Sikka, M. Thomas, and J.D. Whittenberger (TheMinerals, Metals and Materials Society, Warren-dale, PA, 2002) p. 527.36. B. Fischer, Adv. Eng. Mater. 3 (2001) p. 811.37. K. Ito, M. Kumagai, T. Hayashi, and M.Yamaguchi, Scripta Mater. 49 (2003) p. 285.38. Y. Waku (private communication).39. N. Dahotre, ed., Elevated Temperature Coat-ings, TMS Symposia I–IV, 1995, 1997, 1999, and2001 (The Minerals, Metals and Materials Soci-ety, Warrendale, PA).40. M.J. Donachie and S.J. Donachie, Superal-loys—A Technical Guide (ASM International,Materials Park, OH, 2002).41. Superalloys, proceedings of a series of con-ferences held at Seven Springs, PA, 1964–2000,with various editors (The Minerals, Metals andMaterials Society, Warrendale, PA).42. G. Sauthoff, Intermetallics (VCH, Weinheim,1995).43. N.S. Stoloff and V.K. Sikka, Physical Metal-lurgy and Processing of Intermetallic Compounds(Chapman and Hall, New York, 1996).44. J.H. Westbrook and R.L. Fleischer, eds., In-termetallic Compounds: Principles and Practice,Vols. 1 and 2 (1995), Vol. 3 (2002) (John Wiley &Sons, Chichester, UK).







Ji-Cheng (J.-C.) Zhao,Guest Editor of thisissue of MRS Bulletin, isa materials scientist atthe GE Global ResearchCenter in Schenectady,N.Y., where he hasworked since 1995. Hisresearch focuses on thedesign of advanced al-loys and coatings as wellas hydrogen-storagematerials. His particularemphasis is on phase di-agrams, thermodynam-ics, diffusion, andcomposition–structure–property relationships.He developed a diffusion-multiple approach forthe rapid mapping ofphase diagrams andphase properties.

Zhao received his BS(1985) and MS (1988)degrees in materialsfrom the Central SouthUniversity, China, andhis PhD degree in mate-rials from Lehigh Uni-versity (1995). He hasreceived several honors,including the GeislerAward from the EasternNew York Chapter ofASM International andthe Hull Award from GEGlobal Research, and hewas elected a fellow ofASM International in2003. Zhao has pub-lished approximately 45papers and co-editedone book. He also holds17 U.S. patents withabout 20 more pendingand is an associate edi-tor for the Journal ofPhase Equilibria.

Zhao can be reachedat the GE Global Re-search Center, K1-MB239,One Research Circle,Niskayuna, NY 12309,USA; tel. 518-387-4103,fax 518-387-6232, and

e-mail [email protected].

Jack H. Westbrook,Guest Editor of thisissue of MRS Bulletin, isowner and principalconsultant of BrooklineTechnologies, a consult-ing firm in Ballston Spa,N.Y. Westbrook consultsboth on materials andtechnical informationsystems. He was an earlypioneer in research onintermetallic compoundsas potential high-temperature structuralmaterials and has editedsix volumes of collectedworks on this topic.

Westbrook receivedBMetEng and MMetEngdegrees from RensselaerPolytechnic Instituteand a ScD degree inmetallurgy from theMassachusetts Instituteof Technology. He joinedGeneral Electric’s R&DCenter in 1949, where hewas engaged in materi-als research and pro-gram planning for over20 years. In 1971, he wasnamed manager of Ma-terials Information Ser-vices, then a unit ofCorporate Consulting,but subsequently trans-ferred to the R&D Cen-ter. After retiring fromGE in 1985, Westbrookand another ex-GE col-league established theconsulting firm Sci-TechKnowledge Systems,which specialized instudies of technical in-formation systems.When this firm dis-solved in 1991, West-brook foundedBrookline Technologies.

He is a fellow of fourprofessional societies

and a member of theNational Academy ofEngineering. He has re-ceived numerous na-tional and internationalawards for his work.Two of these, ASM’sCampbell Lecture andtheir Sauveur Achieve-ment Award, werespecifically for his workon intermetallics. West-brook has a strong inter-est in the history ofscience and technologyand has published ex-tensively in this field aswell. For several years,he has served MRS as amember of the MRSBulletin editorial boardand as a book reviewer.

Westbrook can bereached at BrooklineTechnologies, 5 Brook-line Road, Ballston Spa,NY, 12020-3523, USA;tel. 518-885-8840 ande-mail [email protected].

Bernard P. Bewlay is amember of the scientificstaff at General ElectricGlobal Research in Sch-enectady, N.Y. His workis focused on fundamen-tal and applied researchof processing–structure–property relationships in

high-temperature mate-rials, refractory metals,refractory-metal com-posites, coatings, and ti-tanium alloys. Afterreceiving his DPhil de-gree in metallurgy andmaterials science fromOxford University in1987, he joined Rolls-Royce, moving to GEGlobal Research in 1988.He is a member of theMaterials Research Soci-ety, the Microscopy So-ciety of America, andthe Institute of Materi-als. He is also a fellowof ASM International.He has published morethan 100 papers andholds 32 patents.

Bewlay can bereached at GE GlobalResearch Center, K1-MB271, One ResearchCircle, Niskayuna, NY12309, USA; tel. 518-387-6121, fax 518-387-5576,and e-mail [email protected].

François Christin is pro-gram engineer and man-ager of ceramic-matrixcomposites at SnecmaPropulsion Solide (SPS)in Le Haillan, France.He graduated in 1975from ENSCT (Toulouse)

and in 1979 obtained hisPhD degree from Uni-versité Bordeaux 1.

After graduation,Christin started workingfor SEP. For 10 years, hewas in charge of the de-velopment and industri-alization of a new processexecuted during his PhDthesis known as chemi-cal vapor densification ofsilicon carbide. He thencontinued as managerfor research and develo-pment in composite ma-terials for 10 years, duringwhich time he developeda new materials familywith his team and opti-mized characterizationmethods and modeling.Christin is currently incharge of the Researchand Technologies Pro-gram at Snecma Mo-teurs (Aeronautic andSpace Engines).

Christin can bereached at SnecmaPropulsion Solide, LesCinq Chemins, 33187 Le Haillan, France.

Lesley A. Cornish hasbeen Head of the Ad-vanced Materials Groupin the Physical Metal-lurgy Division at Mintek(Randburg, South Africa),


45. High Temperature Ordered Intermetallic Al-loys, various editors, Vols. I (1985), II (1987), III(1989), IV (1991), V (1993), VI (1995), VII (1997),VIII (1999), and IX (2001) (Materials ResearchSociety, Warrendale, PA).46. D.B. Miracle and S.L. Donaldson, eds., ASMHandbook Volume 21: Composites (ASM Interna-

tional, Materials Park, OH, 2001).47. R. Darolia, J.J. Lewandowski, C.T. Liu, P.L.Martin, D.B. Miracle, and M.V. Nathal, eds.,Structural Intermetallics (ISSI-1) (The Minerals,Metals and Materials Society, Warrendale, PA,1993); M.V. Nathal, R. Darolia, C.T. Liu, P.L.Martin, D.B. Miracle, R. Wagner, and M.

Yamaguchi, eds., Structural Intermetallics (ISSI-2) (1997); K.J. Hemker, D.M. Dimiduk, H.Clemens, R. Darolia, H. Inui, J.M. Larsen, V.K.Sikka, M. Thomas, and J.D. Whittenberger, eds.,Structural Intermetallics (ISSI-3) (2002). ■■


Ji-Cheng (J.-C.) Zhao Jack H. Westbrook Bernard P. Bewlay





Madan G. Mendiratta Roger Naslain John R. Nicholls



since 2001 as well as anhonorary professor atthe University of theWitwatersrand in Johan-nesburg. From 1989 to2001, she lectured at theUniversity of the Wit-watersrand, and beforethat (1985–1989), sheworked for the UnitedKingdom Atomic EnergyAuthority.

Cornish studied met-allurgy and materials atthe University of Birm-ingham and also ob-tained her PhD degreethere. Her interests arein the calculation andexperimental derivationof phase diagrams, therelationship of structureand properties, and thedevelopment of alloysfor special applications.Among other areas, she has worked withplatinum-group-metalphase diagrams,platinum-based alloys,additions of vanadiumto WC-Co hard metals,and additions of PGMsto stainless steels.

Cornish can bereached at the PhysicalMetallurgy Division,Mintek, Private BagX3015, Randburg, SouthAfrica; tel. 27-(0)-11-709-4474; fax 27-(0)-11-709-4480, and [email protected].

Dennis M. Dimiduk isthe research leader foradvanced metallics atthe Materials and Manu-facturing Directorate ofthe Air Force ResearchLaboratory in Dayton,Ohio. He leads explo-ration and basic researchon high-temperaturestructural alloys, and hiswork has sought an un-derstanding of disloca-tion mechanisms inintermetallic alloys. Formore than a decade,Dimiduk’s work focusedon inserting the �-titanium aluminidesinto aerospace serviceand exploring refractory-metal silicides as high-

temperature structuralalloys for propulsionsystems. His researchalso seeks to understandthe influence of chemistryon microstructural evo-lution and deformationin alloys through simu-lation methods. Thosetechniques have beenapplied to advance �-titanium aluminides,and are now being di-rected toward superalloys.

Dimiduk received hisBS in materials scienceand engineering fromWright State Universityand his MS and PhD de-grees in metallurgicalengineering and materialsscience from CarnegieMellon University. For26 years, he has beenwith the AFRL (and itspredecessors). He hasauthored or co-authoredmore than 120 technicalpapers and 10 patentson advanced metals andprocesses. He is a mem-ber of the editorial boardfor the journal Inter-metallics and is an adjunctprofessor at Wright Stateand Ohio State. Dimidukis a fellow of ASM Inter-national and of the AFRL.Currently, he is continu-ing to investigate com-putational materialsscience and engineeringmethods for acceleratedinsertion of metals intoservice.

Dimiduk can bereached at USAF WrightLaboratory, WL-MLLM,2230 10th Street, Suite 1,Bldg. 655, Wright Patter-son Air Force Base, OH45433, USA; tel. 937-255-9839, fax 937-255-3007,and e-mail [email protected].

Bernd Fischer is a pro-fessor of materials sci-ence at the University ofApplied Sciences Jena inGermany. He studiedmaterials technology atthe Technical UniversityChemnitz and receivedhis doctorate degree in1971. After that, he

started to work in thefield of high-temperaturematerials, especiallyplatinum-group metals,at the Friedrich SchillerUniversity. He investi-gated the corrosion re-sistance of platinummaterials in glass-meltingplants and the interactionbetween molten glassand platinum materials,in particular, the influenceof molten glass on crys-tal structure and on thehigh-temperature prop-erties of platinum alloys.After more than 25 yearsof research and teachingat Jena, Fischer wasawarded the chair ofmaterials science in 1992.He was dean of the Fac-ulty of Materials Technol-ogy from 1992 to 1994and pro-rector for researchfrom 1994 to 1997. Duringthe last few years, his re-search focused on thedevelopment and char-acterization of platinumalloys, especially oxide-dispersion-hardenedplatinum materials. Hehas also investigatedmechanical high-

temperature properties(stress rupture strengthand creep behavior) ofrefractory metals (rhe-nium, tungsten, molyb-denum, and their alloys)at temperatures in therange of 1500–3000�C.

Fischer can be reachedat FH Jena—Universityof Applied Sciences,Dept. of Materials Tech-nology, Carl-Zeiss-Promenade 2, D-07745Jena, Germany; tel. 49-(0)-364-120-5475; fax 49-(0)-364-120-5476, ande-mail [email protected].

Melvin R. Jackson hasbeen a researcher in theCeramic and MetallurgyTechnology Laboratoriesof the General ElectricGlobal Research Centerin Schenectady, N.Y.,since 1972. After receivinga PhD degree in metal-lurgy and materials en-gineering from LehighUniversity, he workedwith INCO for a year.He has concentrated hisresearch on high-temperature systems,

phase equilibria, inter-diffusion, and interac-tion. His current areas ofinterest include the be-havior of refractory-metalcomposites, coatings,and metallic intercon-nects for solid-oxide fuelcells. He is the author orco-author of 105 papersand articles, holds 111U.S. patents, and wasawarded GE’s CoolidgeFellowship in 1995.

Jackson can be reachedat GE Global Research,Rm. MB223, P.O. Box 8,Schenectady, NY 12309,USA; tel. 518-387-6362,fax 518-387-7495, ande-mail [email protected].

John J. Lewandowski iscurrently the LeonardCase Jr. Professor of Ma-terials Science and Engi-neering and Director ofthe Mechanical Charac-terization Facility atCase Western ReserveUniversity, where he hasbeen on the faculty since1986. His publicationsand presentations num-ber in excess of 150 and

Dennis M. DimidukFrançois Christin Lesley A. Cornish






350, respectively, andare primarily in theareas of processing–structure–property rela-tionships in ferrous andnonferrous engineeringmaterials; the effects ofsuperposed pressure ondeformation and frac-ture; fatigue and frac-ture of intermetallics andcomposites, bulk metal-lic glass, and layered/laminated materials; de-formation processing;and blast-resistant mate-rials and structures.Lewandowski receivedhis BS, ME, and PhD de-grees in metallurgicalengineering and materi-als science at CarnegieMellon University,where he was a HertzFoundation fellow. Twoyears were spent as aNATO postdoctoral fel-low in the Departmentof Materials Science andMetallurgy at CambridgeUniversity, England,working with J.F. Knotton fracture and fatigueof engineering metals.He was recently elected

an overseas fellow atChurchill College, Uni-versity of Cambridge.Other honors includeASM fellow, the NSFPresidential Young In-vestigator Award, theSAE Ralph R. Teetor Ed-ucational Award, theASM Bradley StoughtonAward for Young Teach-ers, the ASM ResearchSilver Medal, the CTSCTechnical EducatorAward, and the CharlesHatchett Award fromthe Institute of Metalsfor work on Nb.

Lewandowski can bereached at Case WesternUniversity, Dept. ofMaterials Science andEngineering, CharlesWhite Metallurgy Bldg., Cleveland, OH44106, USA; tel. 216-368-4234, fax 216-368-8618,and e-mail [email protected].

Madan G. Mendiratta isdirector of the Materialsand Processor Divisionat UES Inc. in Dayton,Ohio. In this capacity, he

provides technical andadministrative manage-ment to a number of re-search programs for theU.S. Air Force. His re-search focus for the pastseveral years has beenon the development ofmaterials for high-temperature structuralapplications in ad-vanced jet engines.These materials includemetallic and intermetal-lic complex multiphasesystems. Mendiratta hasconducted research onprocessing, phase rela-tions, microstructuralevolution, mechanicalproperties, and oxida-tion mechanisms. Hehas published more than200 papers in interna-tionally refereed journals,written three book chap-ters, and holds fivepatents. Mendiratta re-ceived his PhD degreein materials science andengineering mechanicsfrom Rutgers Universityin 1970.

Mendiratta can bereached at UES Inc.,

Materials Research Divi-sion, 4401 Dayton-XeniaRoad, Dayton, OH45432-1894, USA; tel.937-255-9832, fax 937-656-7292, and [email protected].

Roger Naslain is profes-sor emeritus at the Uni-versité Bordeaux 1 inPessac, France. UntilSeptember 2002, he wasdirector of the Laboratoryfor ThermostructuralComposites (LCTS), ajoint institution involvingthe university, CNRS(the National Center forScientific Research),Snecma, and CEA (theFrench Atomic EnergyCommission). His re-search focuses on pro-cessing, materials design,and properties of ceramicfibers and ceramic-matrixcomposites and theirapplication in the spaceand aeronautic industries.He is a member of theAcademy of Ceramics(and laureate of its 2000prize), Academia Eu-ropae, the American Ce-ramic Society (fellowand associate editor),the European CeramicSociety, and the Euro-pean Society for Com-posite Materials (formervice president). He cre-ated and co-chaired aseries of InternationalConferences on High-Temperature Ceramic-Matrix Composites(Bordeaux, Santa Bar-bara, Osaka, Munich,and Seattle). He has edi-ted nine books or spe-cial issues of scientificjournals, published300 articles, and holds16 patents.

Naslain can be reachedat the Laboratoire desComposites Thermo-structuraux, UMR 5801(CNRS-SNECMA-CEA-UB1), Université Bor-deaux 1, 3 Allée de laBoétie, 33600 Pessac,France; tel. 05-56-844-

706 and e-mail [email protected].

JohnR.Nicholls is professorof coatings technology atCranfield University inthe United Kingdom. Hehas considerableexperience in high-temperature surface engineering and corrosionof materials at hightemperature and hasbeen involved in coatingstechnology since 1978.He is a materials scientistwho has undertakenwork in the areas of coat-ing deposition (PVD,CVD, and HIP surfacing),structure characterization,and the design of novelmultilayered and gradedstructures. He has astrong interest in the sta-bility of intermetallics aspart of a coating system,the design of smartcorrosion-resistant coat-ings, and the manufactureof low-thermal-conductivity thermal-barrier coatings. Thishas included studies ofthermal conductivity inTBCs, the role of dopantadditions and advancedprocessing, bond-coatoxidation, erosion, andforeign-object damage.John Nicholls is activelyinvolved in the designof corrosion life modelsthat take into accountthe stochastic nature ofhigh-temperature corro-sion processes. To thisend, he has also carriedout fundamental studieson oxidation, corrosion,and erosion mechanismsand their interactions.He has managed numer-ous research projects,published more than170 papers, edited sev-eral books, and is thejoint holder of two coat-ing patents. He is amember of the SurfaceEngineering and HighTemperature MaterialsPerformance Commit-tees of the Institute ofMaterials and immedi-


P.R. SubramanianJohn H. Perepezko Rainer Völkl

Melvin R. JacksonBernd Fischer John J. Lewandowski







ate past chairman of theInstitute’s Surface Engi-neering Committee.

Nicholls can be reachedat Cranfield University,Bldg. 61, Cranfield, Bed-fordshire, MK43 0AL,UK; tel. 44-(0)-123-475-4039 and [email protected].

John H. Perepezko is theIBM–Bascom Professorof Materials Science andEngineering at the Uni-versity of Wisconsin—Madison. His researchfocuses on phase-transformation behavior,especially during the nu-cleation stage of reactions,microstructure–propertyrelationships duringmaterials processing,high-temperature inter-metallic alloys and coat-ings, solidification, phasestability, modeling, andmaterials design. He re-ceived his PhD degreein metallurgy and mate-rials science from

Carnegie Mellon Univer-sity and has also workedat the U.S. Steel ResearchLaboratory. He washonored with theForschungpreise fromthe Alexander vonHumboldt Foundation.He is a fellow of ASMInternational and TMSand an editor for ScriptaMaterialia.

Perepezko can bereached at the Universityof Wisconsin—Madison,Dept. of Materials Scienceand Engineering, 1509University Ave., Madison,WI 53706-1595, USA; tel.608-263-1678, fax 608-262-8353, and [email protected].

P.R. Subramanian is amaterials scientist atGeneral Electric GlobalResearch in Schenectady,N.Y. After obtaining hisMS and PhD degrees inmaterials science andengineering from IowaState University, he didpostgraduate work at

Carnegie Mellon Univer-sity. Prior to joining GE,he worked for UES Inc.for 12 years in the areaof aerospace materialswithin the Air Force Re-search Laboratory atWright-Patterson AirForce Base, Ohio. Hehas also served as anadjunct professor in me-chanical and materialsengineering at WrightState University, wherehe has developed andtaught courses on high-temperature materials,corrosion, diffusion, andmulticomponent phasediagrams. His currentareas of research includeprocessing–microstruc-ture fundamentals innanostructured metallicsystems, structural ap-plications of refractory-metal systems, andfriction stir welding ofaerospace alloys. Subra-manian is a fellow ofASM International. Hehas over 70 publicationsin alloy development,

microstructure–propertyrelationships, phasetransformations, andprocessing, holds sixU.S. patents, and is theco-editor of Binary AlloyPhase Diagrams Handbook,published by ASMInternational.

Subramanian can bereached at the GE GlobalResearch Center, Schenec-tady, NY 12301, USA.

Rainer Völkl is a seniorlecturer and senior re-searcher at the Universityof Bayreuth, Germany.His main scientific inter-ests are the physicalmetallurgy and technol-ogy of platinum-groupmetals. Völkl studiedmaterials science at theTechnical University ofBerlin and Ecole Centralde Lyon, France. In1997, he received a PhDdegree in materials sci-ence for his work onconvergent-beam elec-tron diffraction and fi-nite element simulation

of internal stress fieldsin nickel-based superal-loys. From 1997 to 2003,he was at the Universityof Applied Sciences Jenaand the Friedrich SchillerUniversity in Jena, work-ing together with SchottGlas and W.C. HeraeusGmbH & Co. on severalR&D projects involvingplatinum, rhodium, andiridium alloys. For 2003and 2004, Völkl will jointhe research group ofDr. Harada at the Na-tional Institute for Mate-rials Science in Tsukuba,Japan, as a fellow of theJapan Society for thePromotion of Science.

Völkl can be reachedat the University ofBayreuth, Dept. ofMetallic Materials,Ludwig-Thoma-Strasse36b, D-95440 Bayreuth,Germany; tel. 49-(0)-921-55-5553; fax 49-(0)-921-55-5561, and [email protected]. ■■

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