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`Ultrahigh-Temperature Materials for Jet
`Engines
`
`ARTICLE · AUGUST 2003
`
`DOI: 10.1557/mrs2003.189
`
`CITATIONS
`96
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`1 AUTHOR:
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`Ji-Cheng Zhao
`The Ohio State University
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`Available from: Ji-Cheng Zhao
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`GE-1017.001
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`...a...m.::';i;*,%;'::.:".é::.':::L°;.':t“J
`
`A Publication of the Materials Flasaarch Society
`
`September 2003, Volume 28, No. 9
`
`Ultrahigh-Temperature
`Materials for Jet Engines
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`GE-1017.002
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`

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`www.mrs.org/publications/bulletin
`
`Ultrahigh-
`Temperature
`Materials for Jet
`Engines
`
`J.-C. Zhao and J.H.Westbrook, Guest Editors
`
`Abstract
`This 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 research
`and development.The individual articles that follow review achievements in four different ma-
`terial classes (three in situ composites—based on molybdenum silicide, niobium silicide, and
`silicon carbide, respectively—and high-melting-point platinum-group-metal alloys), as well as
`advances 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 challenges
`ahead 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-barrier
`coatings, toughness, ultrahigh-temperature materials.
`
`This year marks the centennial of the
`Wright brothers’ first flight. In the second
`half of the last century, aircraft powered
`by jet engines came to dominate both
`civilian and military flights, and they con-
`tinue to have tremendous impact on the
`economy and on our lives (e.g., aircraft
`turbine engines are the single largest U.S.
`export product).
`The history of the jet engine goes back
`much farther than one would suppose.
`Jacques Etienne Montgolfier was the first
`to propose reaction propulsion for aircraft
`in 1783. His concept was intended for a
`balloon rather than an airplane and more
`for steering than main propulsion. The first
`patent for a turbine engine appeared in
`1791; it was intended for use on a horseless
`carriage (automobile). Charles de Leuvrié
`first suggested the idea for a jet-powered
`monoplane in 1865, but it was not until
`1928 that Frank Whittle, a 21-year-old
`Royal Air Force cadet, advanced the idea
`of jet propulsion for aircraft in a published
`thesis. Although his concept was rejected
`by 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 an
`airplane (the Gloster E2) on May 15, 1941.
`Meanwhile, an independent parallel effort
`was going forward in Germany. Hans von
`Ohain obtained a patent for a jet engine on
`November 10, 1935. With backing from
`Ernst Heinkel, he built the He S3B engine,
`which successfully powered an airplane,
`the He 178, on August 27, 1939. Both of
`these developments came too late to have
`a significant impact on World War II, al-
`though some military jets were flown in
`the 1940s. The commercial significance of
`the new mode of power was apparent,
`and in 1952, the British Overseas Airways
`Co. (BOAC) inaugurated the first sched-
`uled jet passenger service. In 1992, Ohain
`and Whittle shared the Draper Prize for
`“early jet development and contributions
`to mankind.” Readers may be interested
`in their biographies1,2 and in another
`book3 that clearly explains the fundamen-
`tals of a jet engine.
`The need in any engine for materials
`with strength at high temperatures was
`recognized early, but the first step was to
`
`622
`
`use alloys already known for their modest
`high-temperature strength and oxidation
`resistance, such as the Ni-Cr alloys intro-
`duced by Marsh in 1906. Only in the late
`1930s and early 1940s, with the introduc-
`tion of the jet engine, was a concerted re-
`search effort launched, principally by the
`Mond Nickel Co. in the United Kingdom,
`to develop alloys particularly for this pur-
`pose. The history of this development was
`sketched in a recent review.4 Present-day
`alloys for this application, Ni-based super-
`alloys, evolved during a period of 70 years
`or more through small incremental changes
`contributed by engine manufacturers, ma-
`terials producers, and materials research
`and development specialists. These alloys
`are composed of Ni3Al (␥´) precipitates in
`a Ni (␥) matrix with admixtures of 10–12
`other elements dissolved in one or both of
`the major phases. The current alloys oper-
`ate for thousands of hours under loads on
`the order of 140 MPa at 85% of their melting
`point. 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 with
`composition or processing, nor advances
`in turbine design (e.g., more complex
`cooling systems) will yield the improve-
`ments demanded by engine designers. We
`still need substantially improved high-
`temperature materials that can only come
`from a completely different materials class.
`The jet engine is a very complex yet op-
`erationally simple device. Figure 1 shows
`a GE 90-115B engine, the most powerful
`jet 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 rotating
`mandrel on which a series of disks (rotors,
`wheels) are mounted. Attached to the pe-
`ripheries (perimeters/rims) of the disks
`are the blades (either compressor blades
`or turbine blades). The vanes duct the air
`into appropriate directions to effectively
`propel the blades. Alternating rows of
`vanes and blades are arranged in both the
`compressor and turbine sections. As the
`air is compressed, its temperature rises; it
`is then mixed with fuel and burned in the
`combustor to raise the temperature. The
`high-temperature, high-pressure (high-
`energy) gas coming out of the combustor
`is ducted by the first-stage, high-pressure
`turbine (HPT) vanes to propel the first-
`stage HPT blades. The efficiency and per-
`formance of the jet engine are strongly
`dependent on the highest temperature in
`the engine—the inlet temperature of the
`HPT—and it is the high-temperature ca-
`pability of these parts that is critical. To
`achieve higher thrust, higher operating
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`MRS BULLETIN/SEPTEMBER 2003
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`Ultrahigh-Temperature Materials for Jet Engines
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`alloys are currently not considered good
`prospects for meeting the need. Perhaps
`significantly, Cr-based alloys were not cov-
`ered in Sims et al.’s 1987 work, Superalloys II.7
`Many monolithic ceramic materials
`possess good strength at jet-engine oper-
`ating temperatures. However, their inher-
`ent brittleness poses a significant challenge
`in withstanding the rigors of assembly and
`the impact damage caused by foreign ob-
`jects that may pass through the engines in
`operation. These materials will have limited
`applications in turbine engines without
`further development of improved mate-
`rials and innovative system architectures.
`Thus, we focus on the remaining two
`classes of potential materials: intermetallic
`compounds and composites. It is these
`two groups that are the subjects of the de-
`tailed reviews that follow in this issue of
`MRS 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 an
`engineering point of view to be the most
`mature 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 the
`low-pressure turbine and static parts of
`the 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 a
`1993 engine test of a low-pressure fan with
`98 TiAl blades was successful. The prob-
`lems that remain include low room-
`temperature ductility (1–2%), low fracture
`toughness, high stress-sensitivity of fa-
`tigue life, and high manufacturing cost for
`finished parts.
`NiAl has a number of attractive proper-
`ties for jet-engine applications, such as a
`high melting point (⬃1650⬚C), good thermal
`conductivity, low density, and intrinsic oxi-
`dation resistance. With suitable alloying
`(Ta ⫹ Cr), good strength properties at tem-
`peratures higher than 1000⬚C can be
`achieved. Alloy parts based on this inter-
`metallic have been successfully made by a
`variety of processes (e.g., investment cast-
`ing, powder metallurgy, hot extrusion,
`and injection molding). Tests for applica-
`tion as static parts for stationary turbines
`have been successful. In NiAl alloy devel-
`opment for jet-engine applications, both
`directionally solidified eutectics and poly-
`crystalline multiphase structures have
`been explored. Serious consideration for
`engine applications will require better
`toughness at room temperature and higher
`creep strength at high temperatures. Re-
`cent summaries of the status of NiAl for
`engine applications may be found in Mir-
`
`Figure 1. (a), (b) Photographs of a high-pressure turbine (HPT) vane and a HPT blade of a
`jet engine. (c) Schematic arrangement of the stationary vanes relative to the rotating blades
`within the engine. (d) Illustration of the GE 90-115B jet engine, showing its various
`components. (e) Pressure and temperature trends from the front to the back of the engine.
`
`temperatures must be realized. To achieve
`higher efficiency, engines must be made
`significantly lighter without loss of thrust.
`In either case, it is obvious that completely
`new families of materials must be devel-
`oped, ones with higher melting points and
`greater intrinsic strength.
`There are only four categories of ma-
`terials that can be considered: refractory
`metals, monolithic ceramics, intermetallic
`compounds, and composites (natural or
`synthetic).
`
`The first category can be immediately
`ruled out. None of the refractory metals is
`sufficiently oxidation-resistant, and all of
`them, with the exception of chromium, are
`substantially denser than present-day Ni-
`based alloys. Chromium, while having the
`advantage of a lower density than nickel,
`is only marginally tough at room tempera-
`ture and is subject to nitrogen embrittlement
`when exposed to air at high temperatures.
`Klopp5 and Ro et al.6 summarized the
`progress made with Cr-based alloys; these
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`MRS BULLETIN/SEPTEMBER 2003
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`Ultrahigh-Temperature Materials for Jet Engines
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`acle and Darolia,12 Noebe and Walston,13
`and several other papers.14–17
`The PGM-based intermetallic alloys
`that have been studied for possible appli-
`cation as high-temperature structural ma-
`terials fall into two classes: those that are
`isomorphous with Ni3Al (e.g., Pt3Al), and
`those that are isomorphous with NiAl (e.g.,
`RuAl). In both cases, the advantages of
`PGM-based intermetallics over Ni-based
`superalloys are a significantly higher melt-
`ing point (⬃1500⬚C for Pt3Al and ⬃2100⬚C
`for 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 has
`been focused on Pt- and Ru-based com-
`pounds, but there have been some studies
`of Ir-based21 and Rh-based22 materials.
`Progress toward the desired properties has
`been either by alloying to improve strength
`and reduce density or by oxide-dispersion
`strengthening (ODS). In this issue, Cornish
`et al. review current activities and achieve-
`ments with each approach.
`Composite materials are defined23 as a
`macroscopic combination of two or more
`distinct materials having a recognizable
`interface between them. More particularly,
`structural composites are those in which a
`continuous matrix phase bonds and pro-
`vides toughening characteristics to an array
`of pieces of a stronger, stiffer reinforcement
`phase. Structural composites may be formed
`by artificially bringing together a suitable
`combination of matrix and reinforcement
`phase (as in the case of glass-fiber-
`reinforced polymers) or produced natu-
`rally by suitable processing of a carefully
`selected composition (so-called in situ com-
`posites). All three composite systems re-
`viewed here fall into this category of in situ
`composites. All are silicon-rich, which low-
`ers density and provides a basis for oxida-
`tion resistance, but they differ in the nature
`of the reinforcing phase or phases. Dimiduk
`and Perepezko review achievements with
`in 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 are
`compared in Figures 2 and 3.24–37 The
`reader is cautioned that the data for the
`different materials were not necessarily
`obtained under comparable conditions
`and that all materials shown are under
`continuous development with progres-
`sively improving properties.
`Although all of the materials discussed
`in this issue show promise as ultrahigh-
`temperature materials for advanced jet en-
`gines, there is no clear winner among them
`
`Figure 2. The oxidation/recession rate of various ultrahigh-temperature materials discussed
`in this issue of MRS Bulletin.The data were obtained from References 24–29. The best
`published data were plotted for each class of materials. The recession rate is a good figure
`of merit for oxidation resistance, as it measures the material loss in thickness by oxidation
`at certain temperatures and time periods. The material loss is usually by formation and
`spallation of a thermally grown oxide scale, or by evaporation of the metal and oxide in the
`case of platinum-group metal alloys and Mo-Si-B. The results on Mo-Si-B are only for one
`alloy (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 for
`ceramic-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 combustion
`conditions.28 The oxidation data were not obtained under identical conditions, therefore this
`figure 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.
`
`so far. Relatively speaking, the develop-
`ment of Mo-Si-B, Nb-silicide-based com-
`posites, and PGM-based alloys is still in its
`infancy, while the development of CMCs
`has a much longer history. Each class of
`materials has its own merits and draw-
`backs, as briefly summarized here and
`discussed in the respective articles.
`䊏 SiC/SiC Ceramic-Matrix Composites
`are the closest to the long-term engine test-
`ing stage; several engine tests with CMCs
`as combustion chambers have been per-
`formed on land-based gas turbines, and
`similar efforts for jet engines are currently
`under way. Their strength is relatively low,
`even on a density-normalized basis. For
`well-designed systems, the good impact
`resistance and stability at high operating
`temperatures make this system an attrac-
`tive option; significant design effort will
`be required to take full advantage of the
`
`properties as well as to master the chal-
`lenges poised by mating CMCs with
`metallic components. Significant progress
`has been made in environmental-barrier
`coatings to combat the SiO2 evaporation
`problem in high-velocity water-vapor
`environments. Cost, reliability, estimation
`of component life, and the manufacture
`of complex shapes are among the chal-
`lenges requiring continued attention and
`development.
`䊏 Nb Silicide Composites show good oxi-
`dation resistance, good resistance to pesting
`(intermediate-temperature pulverization),
`reasonable fracture toughness, good fa-
`tigue resistance, good high-temperature
`strength, good impact resistance, and can
`be cast reasonably well. Good coatings
`have also been developed for these com-
`posites. However, combining high oxida-
`tion resistance with high strength in a
`
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`MRS BULLETIN/SEPTEMBER 2003
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`Ultrahigh-Temperature Materials for Jet Engines
`
`For a bare material to survive in the
`oxidative environment of a high-
`temperature, high-velocity gas stream
`within a HPT, it needs either to form a
`protective oxide scale or to be virtually
`inert, as are the precious metals. Two pro-
`tective oxides, Al2O3 and SiO2, are the best
`candidates as oxide scales. It is this fact
`that dictated the basic compositions of the
`composite materials reviewed here. SiO2
`grows much slower than Al2O3 at high
`temperatures, thus conferring a clear ad-
`vantage, but it evaporates more quickly in
`a high-velocity, moist environment. Com-
`positional modification of the substrate
`materials has not yielded an attractive
`combination of oxidation resistance and
`high-temperature strength. Thus, it is con-
`cluded that all prospective new materials
`for jet-engine blades will require coatings
`to achieve acceptably long life. These coat-
`ings are quite complex materials systems.
`They are designed to serve two main func-
`tions: oxidation protection and thermal
`protection of the substrate material. Other
`layers may be included to provide auxiliary
`functions: bond coats between coating
`layers 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, Nicholls
`describes the current status of the field.
`But what is the future? Despite the
`progress made in understanding the
`problems confronting high-temperature
`structural materials and the ingenious de-
`velopments in composition selection and
`processing for new base materials, the fact
`remains that none of the systems described
`here is in use in aircraft flying today. Con-
`tinued developments will probably produce
`some further property improvements, but
`whether they will be enough to instigate
`wide usage is difficult to say at this point.
`It is critical to have a combined effort by
`materials people and designers to learn to
`work with low-ductility materials. On the
`materials side, we need materials and proc-
`ess improvements that will increase the
`consistency and reliability of performance,
`even at low ductility and toughness levels;
`and on the design side, new concepts must
`be developed that are more forgiving of
`lower-ductility materials. An alternate route
`to success may be to explore completely
`new base systems, perhaps ternary or
`quaternary compounds.
`For those who are new to this subject
`field, we provide this list of suggested
`readings. Superalloys are covered in two
`monographs, those of Sims et al.7 and of
`Donachie and Donachie,40 as well as in the
`
`Figure 3. Comparison of the density-normalized strength of various ultrahigh-temperature
`materials. The data were obtained from References 30–37 and the articles published in this
`issue 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 Nb
`silicide composites, Mo-Si-B, and CMCs are only preliminary, and the low-temperature data
`are 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 of
`materials. The MASC (metal and silicide composite) alloy has a composition of
`Nb-25Ti-8Hf-2Cr-2Al-16Si. Nb-Si Alloy C is an alloy patented by General Electric Co. and is
`described 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.
`
`single composition remains a problem, as
`does manufacturability.
`䊏 Mo-Si-B Composites exhibit excellent
`high-temperature creep strength, out-
`standing high-temperature yield strength,
`and excellent oxidation resistance at tem-
`peratures above 1000⬚C. Among their
`problems are less-than-desirable oxida-
`tion resistance at intermediate tempera-
`tures, poor manufacturability, poor fatigue
`resistance, poor impact resistance, and low
`fracture toughness. Improvements on these
`fronts are required.
`䊏 PGM-Based Alloys show excellent oxi-
`dation resistance with low amounts of al-
`loying additions. Most of the alloys have
`low strengths (both yield and creep rup-
`ture), very high density, and high cost. The
`Ir-based alloys show very high strength, but
`they no longer have the oxidation resistance
`of the PGMs due to high alloying. The de-
`velopment of PGM-based alloys is still in
`its infancy, and there is the potential for
`high strength by both alloying and ODS.
`In order for them to be used in jet engines,
`innovative designs will be required to take
`advantage of the excellent properties of
`
`PGM-based alloys while avoiding the
`problems of high density and cost.
`The strength data of Al2O3/GdAlO3 Eu-
`tectic Composites are shown in Figure 3 as
`a benchmark of oxide–oxide composites.
`Initial work on this material29 shows great
`high-temperature strength, reasonable frac-
`ture toughness (5 MPa m1/2 at room tem-
`perature and 13 MPa m1/2 at 1600⬚C)38 and
`great oxidation resistance (no loss of mate-
`rial even after exposure at 1700⬚C for 1000
`h). But it has a serious drawback—a lack
`of the thermal-shock resistance required
`to survive engine startups and shut-
`downs. It would be a good potential high-
`temperature material if the thermal-shock-
`resistance problem were solved, either by
`engine design or by material improve-
`ment. In addition, the high strength of this
`material only exists in the melt-grown,
`in situ composite where no glassy phase
`exists along interfaces. It would greatly
`improve 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-shape
`blades possible.
`
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`Ultrahigh-Temperature Materials for Jet Engines
`
`recurring Seven Springs Conferences on
`Superalloys volumes.41 Intermetallic com-
`pounds are treated in monographs by
`Sauthoff42 and by Stoloff and Sikka,43 as well
`as in great detail in the three-volume trea-
`tise edited by Westbrook and Fleischer,44
`and in a series of Materials Research Society
`symposia proceedings.45 Composites are
`covered in considerable detail in the re-
`cent ASM Handbook, Vol. 21.46 Finally, the
`International Symposium on Structural
`Intermetallics series, three of which have
`been published so far,47 considers compos-
`ites, intermetallics, and other types of
`high-temperature structural materials.
`Background information and tutorials on
`jet engines and advanced high-temperature
`materials may also be found on the Inter-
`net. Some of these sites are
`䊏 Ultra-Efficient Engine Technology
`(www.ueet.nasa.gov/Engines101.html);
`䊏 Superalloys: A Primer and History
`(www.tms.org/Meetings/Specialty/Su-
`peralloys2000/SuperalloysHistory.html);
`and
`䊏 AZoM—Metals, Ceramics, Polymers,
`Composites, An Engineer’s Resource
`(www.azom.com).
`
`Disclaimer
`The views, opinions, and conclusions
`contained in this introductory article are
`those of the guest editors for this issue and
`should not be interpreted as representing
`the official policies, positions, or endorse-
`ment, either expressed or implied, of
`General Electric Co. or of Brookline Tech-
`nologies, their employers. They also
`should not be interpreted as representing
`the opinions or positions of the other au-
`thors in this issue of MRS Bulletin or of
`their respective institutions.
`
`Acknowledgment
`The authors are pleased to acknowl-
`edge the benefit of critical reviews of a
`draft of this introduction by the authors of
`the other articles in this issue and by
`H. Lipsitt.
`
`References
`1. J. Golley, Genesis of the Jet: Frank Whittle and
`the Invention of the Jet Engine (Airlife Publica-
`tions, the Crowood Press, Wiltshire, UK, 1998).
`2. M. Conner, Hans Von Ohain: Elegance in Flight
`(American Institute of Aeronautics and Astro-
`nautics, Reston, VA, 2002).
`3. K. Hunecke, Jet Engines: Fundamentals of The-
`ory, Design, and Operation (Motorbooks Interna-
`tional, St. Paul, 1998).
`4. J.H. Westbrook, in Dislocations in Solids,
`Vol. 10, edited by F.R.N. Nabarro and M.S.
`Duesbery (Elsevier, Amsterdam, 1996) p. 3.
`5. W.D. Klopp, in The Superalloys, edited by C.T.
`Sims and W.C. Hagel (John Wiley & Sons, New
`York, 1972) p. 175.
`6. Y. Ro, Y. Koizumi, S. Nakazawa, T.
`
`626
`
`Kobayashi, E. Bannai, and H. Harada, Scripta
`Mater. 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 (John
`Wiley & 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 (The
`Minerals, 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 Intermetallic
`Compounds: Principles and Practice, Vol. 2, edited
`by J.H. Westbrook and R.L. Fleischer (John
`Wiley & Sons, New York, 1995) p. 53.
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`
`MRS BULLETIN/SEPTEMBER 2003
`
`GE-1017.007
`
`

`
`
`
`Ultrahigh-Temperature Materials for Jet EnginesUltrahigh-Temperature Materials for Jet Engines
`
`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 Research
`Society, Warrendale, PA).
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`tional, Materials Park, OH, 2001).
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`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,
`Guest Editor of this
`issue of MRS Bulletin, is
`a materials scientist at
`the GE Global Research
`Center in Schenectady,
`N.Y., where he has
`worked since 1995. His
`research focuses on the
`design of advanced al-
`loys and coatings as well
`as hydrogen-storage
`materials. His particular
`emphasis is on phase di-
`agrams, thermodynam-
`ics, diffusion, and
`composition–structure–
`property relationships.
`He developed a diffusion-
`multiple approach for
`the rapid mapping of
`phase diagrams and
`phase properties.
`Zhao received his BS
`(1985) and MS (1988)
`degrees in materials
`from the Central South
`University, China, and
`his PhD degree in mate