High-temperature superconductors for electric power and high-energy physics

The various devices currently being constructed for electric power and high-energy physics applications demand different performance, cost, and geometry requirements of high-temperature superconductors. At Intermagnetics General Corporation, four types of high-temperature superconductors (powder-in-tube Bi-2223, surface-coated Bi-2212, powder-in-tube Bi-2212, and γBa₂Cu₃O_x) are at various stages of development to meet this demand. V. Selvamanickam earned his Ph.D. in materials engineering at the University of Houston in 1992. He is currently a senior materials scientist with Intermagnetics General Corporation. Dr. Selvamanickam is a member of TMS. D.W. Hazelton earned his M.Sc. in mechanical engineering at Union College in 1984. He is currently a senior engineer with Intermagnetics General Corporation. L. Motowidlo earned his Ph.D. in solid state physics at the University of Connecticut in 1981. He is currently a senior staff scientist with Intermagnetics General Corporation. Dr. Motowidlo is a member of TMS. F. Krahula earned his B.S. in mechanical engineering at Hudson Valley College. He is currently a manager with TDO. J. Hoehn, Jr., earned his B.S. in physics at Sienna College in 1990. He is currently a development engineer with Intermagnetics General Corporation. M.S. Walker earned his Ph.D. in physics at Carnegie Mellon University in 1970. He is currently a senior staff scientist with Intermagnetics General Corporation. P. Haldar earned his Ph.D. in materials science at Northeastern University in 1988. He is currently a manager in the Advanced Devices and Systems Division with Intermagnetics General Corporation. Dr. Haldar is a member of TMS.     

The high-volume production of heterojunction bipolar transistors

The insertion of advanced microwave devices into high-volume applications is critically dependent upon a robust and reproducible epitaxial growth technology accompanied with a reproducible process technology. The precise control of the material and device parameters is essential to maintain a high-yield process, which leads to a low-cost product. Although AlGaAs/GaAs heterojunction bipolar transistors have been widely demonstrated in many company research laboratories and universities, the transition from a laboratory environment to high-volume production requires a thorough understanding of the metalorganic chemical vapor deposition growth process and its correlation with device performance. In this work, high-performance AlGaAs/GaAs heterojunction bipolar transistors grown by MOCVD with excellent control in the device parameter tolerances have been demonstrated in very high volumes. N. Pan earned his Ph.D. in electrical engineering at the University of Illinois in 1988. He is currently chief scientist at Kopin Corporation. Dr. Pan is a member of TMS. D. Hill earned his M.S. in materials science at the Polytechnic Institute of New York in 1986. He is currently vice president of epioperations at Kopin Corporation. Mr. Hill is also member of TMS. C. Rose earned his M.S. in advanced manufacturing engineering at Worcester Polytechnic Institute in 1990. He is currently a quality assurance engineer at Kopin Corporation. R. McCullough earned his A.S. in mechanical design engineering at Wentworth Institute of Technology in 1970. He is currently engineering manager at Kopin Corporation. P. Rice earned his BSEET in electrical engineering at Wentworth Institute of Technology in 1990. He is currently a characterization engineer at Kopin Corporation. D.P. Vu earned his Ph.D. in solid-state physics at Louis Pasteur Institute in 1983. He is currently a principal scientist at Kopin Corporation. K. Hong earned his Ph.D. in electrical engineering at the University of Michigan in 1996. He is currently an electronic design engineer at Rockwell Semiconductor Systems. C. Farley earned his Ph.D. in engineering at the University of Texas at Austin in 1986. He is currently manager, advanced device technology, at Rockwell Semiconductor Systems.     

A metallurgical assessment of SnPbAg solder for GaAs power devices

In this study, solder-based die-attach processes used to affix GaAs devices to heat-spreading carriers were investigated. The solder microstructures were assessed, focusing on void formation, the response of the solder, the backsurface metallization, and the carrier plating to die attachment and reflow thermal processes. Voided regions were found in all solder joints, with a dramatic sensitivity to temperature cycles. Gold-tin alloy phases were found to dominate the solder microstructure for all of the configurations. The total thermal budget was a critical issue in the formation and transformation of various phases as expected for low-melting-point alloys. The NiV-Au backmetal system was investigated to determine the suitability for die attachment. J.M. Parsey, Jr., earned his Ph.D. in materials science at the Massachusetts Institute of Technology in 1982. He is currently a section manager, advanced materials, at Motorola ESTL. Dr. Parsey is also a member of TMS. S. Valocchi earned her M.S. in mechanical engineering/thermal sciences at Arizona State University in 1989. She is currently a process engineer at Motorola. W. Cronin earned his B.Sc. in electrical engineering at Arizona State University in 1979. He is currently a section manager, metals and thinning, at Motorola. J. Mohr earned his M.S. in materials science at Arizona State University in 1990. He is currently a senior technologist at Motorola. B.L. Scrivner earned his B.S. in business administration at the University of Phoenix in 1994. He is currently a product manager at Motorola. K. Kyler earned his B.S. in chemistry at Brigham Young University in 1987. He is currently a process development engineer at Motorola PCRL.     

Advancements in MEMS materials and processing technology

From achievements in display imaging to air bag deployment, microelectromechanical systems are becoming more commonplace in everyday life. With an abundance of opportunities for innovative R&D in the field, the research trends are not only directed toward novel sensor and actuator development, but also toward further miniaturization, specifically achieving micro- and nanoscaled integrated systems. R&D efforts in space, military, and commercial applications are directing specific research programs focused on the area of materials science as an enabling technology to be exploited by researchers and to further push the envelope of micrometerscaled device technology. These endeavors are making significant progress in bringing this aspect of the microelectro-mechanical field to maturation through advances in materials and processing technologies. John D. Olivas earned his Ph.D. in mechanical engineering and materials science from Rice University in 1996. He is currently a program element manager and staff engineer senior for the Advance Interconnect and Manufacturing Assurance Program at the Jet Propulsion Laboratory. Stephen R. Bolin earned his M.S. in materials science from Stanford University in 1970. He is currently staff engineer senior and supervisor of the Applications Engineering Group in the Quality Assurance Office at the Jet Propulsion Laboratory.     

Characterizing and monitoring thin-film processes with spectroscopic ellipsometry

Spectroscopic ellipsometry is routinely used for characterizing and monitoring thin-film processes; currently, the technique is used to monitor a gamut of thin-film processes used in the manufacturing of integrated circuits. In this article, the principles of the technique are reviewed, major requirements for production-worthy tools are discussed, and examples are provided to illustrate the technique’s diverse capability. Arun R. Srivatsa earned his Ph.D. in materials science and engineering from North Carolina State University in 1989. He is currently a staff applications engineer at the FaST division of KLA-Tencor Corporation. Dr. Srivatsa is also a member of TMS. Carlos L. Ygartua earned his M.S. in physics from the University of Texas in Austin and an M.S. in materials science and engineering from Stanford University. He is currently a staff applications scientist at the FaST division of KLA-Tencor Corporation.     

Industrial in-pulp Co-Ni alloy electrowinning at the gecamines Shituru plant

Gecamines is a large mining company in Congo and has been one of the world’s leading cobalt producers for many years, having some of the richest cobalt deposits in the world. This article summarizes cobalt production and process flow-sheet data at the company’s Shituru plant in Congo. As much as 300 tonnes of cobalt alloy with 5–20% nickel content has been produced monthly at the plant through an in-pulp electrolysis process developed by Gecamines. K. Twite earned his Ph.D. in metallurgical engineering at Brussels Free University in 1982. He is currently Shituru plant director at Gecamines. J.-M. Dereydt earned his degree in metallurgical engineering at Liege University in 1967. He is currently plant superintendent at Gecamines. K. Mujinga earned his degree in metallurgical engineering at Lubumbashi University, Congo, in 1982. He is currently a senior metallurgical engineer at Gecamines. P. Louis earned his Ph.D. in chemistry at Brussels Free University in 1976. He is currently project manager at Union Miniere. Dr. Louis is also a member of TMS.     

Computational tools for alloy design: Solid solutions in Gamma-TiAl

Since the early days of quantum mechanics and computer science, computationally based materials design has been the dream of the materials community. Computational methods have become an integral part in the design of drugs, optical, and electronic devices. While computational tools have been developed to study specific structure-property relationships in structural materials, the overall materials problem has remained, for the most part, in the domain of empirical metallurgy. Computational methods can help to identify and understand basic technical factors controlling and limiting the performance of high-temperature structural materials. We have used several computational methods to study the influence of alloy chemistry on the flow behavior of monolithic γ-TiAl. Here, the results of several of these studies and how these insights have or may impact the alloy design process are reviewed. C. Woodward earned his Ph.D. in solid state physica at the University of Illinois, Champaign-Urbana in 1986. He is currently a senior scientist at UES. S.I. Rao earned his Ph.D. in materials science and engineering at Virginia Polytechnic Institute and State University in 1984. He is currently a research scientist at UES. Dr. Rao is a member of TMS. D.M. Dimiduk earned his Ph.D. in materials science and engineering at Carnegie Mellon University in 1989. He is currently a materials engineer at the Air Force Research Laboratory, Wright-Patterson Air Force Base. Dr. Dimiduk is also a member of TMS.     

Applications for grain boundary engineered materials

Advances in automated electron diffraction techniques, microstructural modeling, and the understanding of structure-property relationships for grain boundaries have resulted in the emergence of grain boundary engineering as a formidable tool for cost-effectively achieving enhanced performance in commercial polycrystalline materials (i.e., metals, alloys, and ceramics). In this article, some applications for grain boundary engineering technology that have been developed during the past several years are presented. G. Palumbo earned his Ph.D. in metallurgy and materials science at the University of Toronto in 1989. He is currently a principal research scientist at Ontario Hydro. E.M. Lehockey earned his M.Sc. in materials engineering at the University of Western Ontario in 1988. He is currently a senior research scientist at Ontario Hydro. P. Lin earned his Ph.D. in metallurgy and materials science at the University of Toronto in 1997. He is currently a research scientist at Ontario Hydro.     

Low-cost titanium armors for combat vehicles

The U.S. Army has been using more and more titanium to either increase armor or reduce the weight of current combat vehicles. Future plans call for the development of combat vehicles that are 30 percent lighter. To achieve this target, the future-vehicle hull and turret will have to be manufactured using more ballistically efficient materials than rolled homogeneous steel armor. Lowcost titanium, with its good mechanical, ballistic, and corrosion properties and acceptable fabricability, offers the overall best afternative to achieving this objective. Jonathan S. Montgomery earned his Ph.D. in materials science at Northwestern University in 1990. He is currently a materials research engineer at the Army Research Laboratory. Dr. Montgomery is a member of TMS. Martin G.H. Wells earned his Ph.D. in physical metallurgy at the Royal School of Mines, Imperial College, London University, in 1961. He is currently a team leader of metallurgy at the Army Research Laboratory. Dr. Wells is also a member of TMS. Brij Roopchand earned his Ph.D. in metallurgical engineering at the University of Kentucky in 1976. He is currently a materials engineer at the U.S. Army TACOM-TARDEC. James W. Ogilvy earned his B.A. in engineering at Wayne State University in 1951. He is currently retired from his position as a materials engineer at TARDEC.     

The stochastic modeling of solidification structures in alloy 718 remelt ingots

A stochastic numerical approach was developed to model the formation of grain structure and secondary phases during the solidification of nickel-based alloy 718 remelt ingots. The significance of the present stochastic approach is that the simulated phases can be directly compared with actual phases from experiments at two different scales: grain characteristics can be visualized at the macroscale, while the amount, size, and distribution of secondary phases can be viewed at the microscale. The computer becomes a “dynamic metallographic microscope.” Stochastic modeling was applied to simulate the formation of solidification phases (γprimary phase and NbC and eutectic γ-Laves secondary phases) during the solidification of vacuum-arc-remelted and electroslag-remelted alloy 718 ingots. Modeling results, such as pool profile, grain-growth pattern, grain structure (both columnar and equiaxed grains), columnar-to-equiaxed transition, grain size, and secondary dendrite arm spacing, as well as amount, size, and location of both eutectic γ-Laves and NbC phases compared well with experimental data for cast alloy 718. This research demonstrates that the stochastic approaches are relatively fast, comprehensive, and more accurate than the deterministic approaches in predicting the solidification characteristics of remelt ingots and are mature enough to be used effectively by the metal industry for process development and optimization. Laurentiu Nastac earned his Ph.D. in metallurgical and materials engineering at the University of Alabama at Tuscaloosa in 1995. He is currently a senior staff engineer at Concurrent Technologies Corporation. Dr. Nastac is a member of TMS. Suresh Sundarraj earned his Ph.D. in mineral engineering at the University of Minnesota in 1994. He is currently a process modeling engineer for Concurrent Technologies Corporation. Dr. Sundarraj is also a member of TMS. Kuang-O Yu earned his Ph.D. in metallurgical engineering at the University of Kentucky in 1978. He is currently director of research and development at RMI Titanium Company. Dr. Yu is also a member of TMS. Yuan Pang earned his M.S. in mechanical engineering at the University of Akron in 1977. He is currently a principal engineer at Concurrent Technologies Corporation.     

The formability of austenitic stainless steels

This article reports the results of a study to determine the effects of austenite stability, with respect to the strain-induced transformation to martensite, on the formability of 300 series stainless steels. The effects were evaluated as a function of alloy content, deformation temperature, and deformation rate. Three stainless-steel alloys with different nickel contents were evaluated as commercially cold-rolled and annealed sheet products. Tensile tests were performed at temperatures between −60°C and +125°C and at strain rates from 0.00167 s⁻¹ to 0.167 s⁻¹. The combined effects of strain, strain state, deformation-induced temperature changes, and strain rate are considered to explain the interrelationships between martensite formation and limit strains as observed in forming-limit diagrams. S.F. Peterson earned his M.S. in metallurgical and materials engineering from the Colorado School of Mines in 1997. He is currently an engineer at Case Corporation. M.C. Mataya earned his Ph.D. in metallurgy and materials science from Marquette University in 1976. He is currently an engineer at the Rocky Flats Technology Site. D.K. Matlock earned his Ph.D. in materials science and engineering from Stanford University in 1972. He is currently a professor at the Colorado School of Mines. Dr. Matlock is also a member of TMS.     

The heredity of Al-Si-Mg-Mn before and after Remelting

This article reviews the heredity of metals and alloys that occurs in the casting process by studying the relationship of Al-Si-Mg-Mn alloy prior to and following a remelting process. The microstructure and mechanical properties of the samples are discussed. L. Xiangfa earned his Ph.D. in materials science and engineering at Shandong University of Technology in 1996. He is currently a staff member of the Liquid Metals and Heredity Engineering Laboratory (LMHEL) at Shandong University of Technology. B. Xifang earned his M.Sc. in materials science and engineering at Shandong University of Technology in 1983. He is currently a professor and president of the LMHEL. Q. Xiaogang earned his M.Sc. at Shandong University of Technology in 1997. He is currently a staff member of the LMHEL. M. Jiaji earned his Ph.D. in Russia in 1963. He is currently a staff member of the LMHEL.     

Using SALDVI and SALD with multi-material structures

Selective-area laser deposition and selective-area laser-deposition vapor infiltration are two gas-phase solid-freeform techniques capable of the direct fabrication of arbitrary structures. The wide range of available gas precursors allows unique combinations of materials to be achieved in the final shape. Tailoring of the local microstructure can be achieved by carefully controlling processing temperature, gas partial pressure, and other variables. The versatility of the two techniques can be seen in the fabrication of a structure comprising multiple materials. James E. Crocker earned his M.S. in materials science at the University of Connecticut in 1997. He is currently a graduate research assistant at the University of Connecticut. Mr. Crocker is a member of TMS. Shay Harrison earned his B.S. in materials science and engineering at Rice University in 1994. He is currently a graduate research assistant at the University of Connecticut. Mr. Harrison is a member of TMS. Lianchao Sun earned his M.Sc. in materials science and engineering at Central-South University of Technology in 1986. He is currently a Ph.D. candidate at the University of Connecticut. Mr. Sun is a member of TMS. Leon L. Shaw earned his Ph.D. in materials science and engineering at the University of Florida in 1992. He is currently an assistant professor in the Department of Metallurgy and Materials Engineering at the University of Connecticut. Dr. Shaw is a member of TMS. Harris L. Marcus earned his Ph.D. in materials science at Northwestern University in 1966. He is currently director and professor of the Institute of Materials Science at the University of Connecticut. Dr. Marcus is a member of TMS.     

The properties and uses of fluxes in molten aluminum processing

Gaseous and solid fluxes play an important role in the degassing, demagging, and fluxing of aluminum and its alloys. Inert as well as reactive gases, or hexachloroethane, may be used to remove dissolved hydrogen and sodium. Magnesium may be removed by chlorine or an aluminum-fluoride-containing flux. Fluxes based on a KCl-NaCl mixture may be used to cover and protect the metal from oxidation. To recover aluminum from drosses, a more reactive flux containing cryolite or some other fluoride may be used. In this article, the thermodynamics of aluminum melting and refining are analyzed in terms of the behavior of sodium, magnesium, and calcium. The coalescence of aluminum drops in salt fluxes improves with fluoride additions. With increasing MgCl₂ contents in the flux, the effects of NaF and KF additions become much less pronounced. T.A. Utigard earned his Ph.D. in metallurgy at the University of Toronto, Canada, in 1985. He is currently an associate professor at the University of Toronto. Dr. Utigard is a member of TMS. K. Friesen earned her M.A.Sc. in metallurgy and materials science at the University of Toronto in 1997. She is currently a plant metallurgist at Scepter. R.R. Roy earned his Ph.D. in materials science and engineering at Ohio State University in 1994. He is currently a research associate at the University of Toronto. J. Lim earned his M.A.Sc. in metallurgy and materials science at the University of Toronto in 1997. He is currently a Ph.D. candidate at McMaster University. A. Silny earned his Ph.D. in chemistry at the Slovak Academy of Sciences in 1998. C. Dupuis earned his M.Sc. in metallurgical engineering at Laval University in 1997. He is currently a senior scientist at Arvida Laboratories, Alcan International Ltd. Mr. Dupuis is also a member of TMS.     

Using intense plastic straining for high-strain-rate superplasticity

Ultrafine grain sizes may be introduced into bulk samples by using the intense plastic straining technique equal-channel angular pressing. This article describes the principles of equal-channel angular pressing and demonstrates the application of this procedure to attain ultrafine grain sizes in an Al-3Mg solid-solution alloy and a commercial cast Al-Mg-Li-Zr alloy. Provided there is stability of these ultrafine grains at elevated temperatures, as in the Al-Mg-Li-Zr alloy, equal-channel angular pressing may be used as a processing tool to achieve high-strain-rate superplasticity in materials that are not potentially superplastic. These results have important implications for reducing the long production times that are associated with the fabrication of complex parts using superplastic forming. Terence G. Langdon earned his Ph.D. in physical metallurgy at Imperial College, University of London, in 1965. He is currently professor of materials science and mechanical engineering at the University of Southern California, Los Angeles. Dr. Langdon is a member of TMS. Minoru Furukawa earned his D.Eng. in metallurgy at Kyushu University in 1988. He is currently an associate professor at Fukuoka University of Education, Munakata, Japan. Dr. Furukawa is also a member of TMS. Zenji Horita earned his Ph.D. in materials science at the University of Southern California in 1983. He is currently an associate professor of materials science and engineering at Kyushu University, Fukuoka, Japan. Dr. Horita is also a member of TMS. Minoru Nemoto earned his D.Eng. in materials science and engineering at Tohoku University in 1966. He is currently a professor of materials science and engineering at Kyushu University, Fukuoka, Japan. Dr. Nemoto is also a member of TMS.     

The use of titanium in production automobiles: Potential and challenges

Titanium offers a number of attractive features for use in high-production-volume automobiles; however, high cost has been a barrier to application, thus far. This article discusses the potential and challenges for the use of titanium in the family automobile. A.M. Sherman earned his Ph.D. in metallurgy at the Massachusetts Institute of Technology in 1972. He is currently senior staff technical specialist at Ford Motor Company. Dr. Sherman is a member of TMS. C.J. Sommer earned his B.S. in metallurgical engineering at University of Pittsburgh in 1982. He is currently manager of automotive marketing at Timet. F.H. Froes earned his Ph.D. in physical metallurgy at Sheffield University in 1967. He is currently the director of the Institute for Materials and Advanced Processes at the University of Idaho. Dr. Froes is also a member of TMS.     

Metallurgical techniques for more reliable integrated circuits

One of the primary concerns in the manufacture of advanced microelectronic devices is to ensure that metallic contacts and interconnects do not fail by electromigration or stress-induced voiding. This article discusses the possibility of implementing two kinds of beneficial treatments within normal manufacturing processes—treatments that modify grain structure to minimize failures through diffusional flux divergence and treatments that control solute and precipitate distributions in order to avoid undesirable, overaged microstructures at the end of manufacturing. S.H. Kang earned his Ph.D. in materials science and engineering at the University of California at Berkeley in 1996. He is currently a member of the technical staff at Bell Laboratories, Lucent Technologies. J.W. Morris, Jr., earned his Sc.D. in materials science at the Massachusetts Institute of Technology in 1969. He is currently a professor of metallurgy and principal investigator at Lawrence Berkeley National Laboratory. Dr. Morris is a member of TMS. A.S. Oates earned his Ph.D. in physics at the University of Reading, United Kingdom, in 1985. He is currently a manager at Bell Laboratories, Lucent Technologies.     

The development of low-cost TiAl automotive valves

This paper presents the results of a project funded by the Edison Materials Technology Center to develop low-cost titanium aluminide automotive valves. In the course of the project, more than 800 valves were produced using several variations of the permanent-mold casting process. Applying pressure during solidification improved the casting fill; however, none of the permanent mold casting methods produced pore-free as-cast valves. The as-cast microstructures of the valves were much finer than investmentcast microstructures of similar section sizes. The room-temperature tensile properties of the permanent mold castings were superior to those of investment castings of a comparable section size. M.M. Keller earned her M.Sc. in materials engineering at the University of Dayton in 1993. She is currently a Ph.D. student in materials engineering. She is also a member of TMS. P.E. Jones earned her M.Sc. in materials at the University of Dayton in 1993. She is currently a Ph.D. student in materials engineering. She is also a member of TMS. W.J. Porter III earned his M.Sc. in materials engineering at the University of Dayton in 1990. He is currently project engineer at the University of Dayton Research Institute. He is also a member of TMS. D. Eylon earned his D. Sc. in materials engineering at Technion, Haifa, Israel, in 1972. He is currently a professor of graduate materials engineering at the University of Dayton. He is also a member of TMS.     

Fatigue behavior in nickel-based superalloys: A literature review

In this literature review, the present understanding regarding the effects of microstructure, loading conditions, and environments on the fatigue behavior of nickel-based superalloys is reviewed. Authors' Note: Inconel, Incoloy, and Nicalon are registered trademarks. L. Garimella earned his M.S. in materials science and engineering at the University of Tennessee in 1997. He is currently working at an Internet company. Mr. Garimella is a member of TMS. P. K. Liaw earned his Ph.D. in materials science and engineering at Northwestern University in 1980. He is a professor and Ivan Racheff Chair of Excellence in the Department of Materials Science and Engineering at the University of Tennessee. Dr. Liaw is also a member of TMS. D.L. Klarstrom earned his Ph.D. in metallurgical engineering at the University of Wisconsin-Madison. He is currently director of Haynes International. Dr. Klarstrom is also a member of TMS.