Ceramic-metal interfaces and the spreading of reactive liquids

A number of solid-state and liquid-state processing techniques are available for tailoring the properties of a ceramic-metal interface. While many of the techniques are successfully used in industry, the mechanisms for their microstructural formation are not well understood. For situations where a liquid metal is in contact with a solid ceramic substrate, the wetting and spreading behavior of the liquid is critical in determining the final microstructure and properties of the interface, which may control the properties of the component or system. Alan Meier earned his Ph.D. in metallurgical and materials engineering at the Colorado School of Mines in 1994. He is currently an assistant professor of metallurgy and materials engineering in the Ceramic Engineering and Materials Science Department, New York State College of Ceramics, Alfred University. Daniel A. Javernick is a Ph.D. candidate at the Colorado School of Mines. He is currently a graduate research assistant in the Department of Metallurgical and Materials Engineering, Colorado School of Mines. Glen R. Edwards earned his Ph.D. in materials science and engineering from Stanford University. He is a professor in the Department of Metallurgical and Materials Engineering and director of the Center for Welding, Joining and Coatings Research at Colorado School of Mines.     

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.     

Materials challenges in interconnection: Trade-offs for rapid deployment

This article addresses the subtle changes necessary to achieve a margin against an intrinsic failure mechanism in a highly time-constrained development world. The problem of a coefficient of thermal expansion mismatch between a liquid crystal polymer connector and a FR4 substrate was exacerbated by the size, dimensions, and ball-grid array attachment for such a connector. By carefully controlling the solder-mask wall profile, opening, and overhang, it was possible to avoid the time- and resource-consuming option of changing the connector materials. Kris Frutschy earned his Ph.D. in mechanical engineering at Brown University in 1997. He is currently a senior mechanical engineer at Intel Corporation. Ken Kinsman earned his Ph.D. in materials science at Standford University in 1966. He is currently a technology platform manager at Intel Corporation. Dr. Kinsman is also a member of TMS. Zezhong Fu earned his Ph.D. in materials science at the California Institute of Technology in 1993. He is currently a senior engineer at Intel Corporation. Deepak Goyal earned his Ph.D. in materials science and engineering at SUNY at Stony Brook. He is currently a staff packaging engineer at Intel Corporation. Gay Samuelson earned her Ph.D. in biochemistry at the University of Wisconsin-Madison in 1969. She is currently a lab manager at Intel Corporation. Ryan Vogt earned his M.S. in materials science and engineering at the University of Arizona in 1995. He is currently a package quality and reliability engineer at Intel Corporation.     

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.     

The present status of dental titanium casting

Experimentation in all aspects of titanium casting at universities and industries throughout the world for the last 20 years has made titanium and titanium-alloy casting nearly feasible for fabricating sound cast dental prostheses, including crowns, inlays, and partial and complete dentures. Titanium casting in dentistry has now almost reached the stage where it can seriously be considered as a new method to compete with dental casting using conventional noble and base-metal alloys. More than anything else, the strength of titanium’s appeal lies in its excellent biocompatibility, coupled with its comparatively low price and abundant supply. Research efforts to overcome some problems associated with this method, including studies on the development of new titanium alloys suitable for dental use, will continue at many research sites internationally. Toru Okabe earned his Ph.D. in metallurgical and materials engineering at the University of Florida in 1969. He is currently professor and chair of biomaterials science at Baylor College of Dentistry. Dr. Okabe is a member of TMS. Chikahiro Ohkubo earned his Ph.D. in removable prosthodontics and his D.M.D. in dentistry at Tsurumi University in 1989 and 1985, respectively. He is currently an instructor at the School of Dental Medicine at Tsurumi University in Yokohama, Japan. Ikuya Watanabe earned his Ph.D. in dental science at Nagasaki University in 1995. He is currently working at Nagasaki University, Japan. Osamu Okuno earned his Ph.D. in engineering at Waseda University in 1976. He is currently a professor and chair in the Department of Dental Materials Science, School of Dentistry, Tohoku University, Japan. Yukyo Takada earned his Ph.D. in engineering at Waseda University in 1991. He is currently assistant professor in the Department of Dental Materials Science, School of Dentistry, Tohoku University, Japan.     

The strength properties of iron aluminides

For the development of Fe−Al alloys as structural materials, a deep understanding of slip and deformation properties is necessary. In particular, since mechanical properties of the iron aluminides are affected by excess vacancy strengthening as well as the positive-temperature dependence of yield stress, controlling these strength features is essential. In this article, the strength properties of iron aluminides are reviewed. Author’s Note: All compositions are provided in mole percent. Kyosuke Yoshimi earned his Ph.D. in materials science and engineering at Tohoku University in 1997. He is currently a research associate at Tohoku University. Shuji Hanada earned his Ph.D. in materials science and engineering at Tohoku University. He is currently a professor at Tohoku University. Dr. Hanada is also a member of TMS.     

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.     

The effect of preaging on the delayed aging of Al−7Si−0.3Mg

Al−7Si−0.3Mg is a commonly used commercial casting alloy because of its excellent castability combined with good mechanical properties. The post-casting heat treatment isone factor that affects the mechanical properties; during heat treatment, a delay between solutionizing and artificial aging (delayed aging) leads to a reduction in hardness, ultimate tensile strength, and yield strength in the alloy. The investigation reported here was aimed at understanding the extent to which the harmful effect of delayed aging on hardness/strenght can be nullified. The results obtained were explained using Pashley’s kinetic model. S. Murali earned his Ph.D. in physical and mechanical metallurgy from the Indian Institute of Science (Metallurgy Department) in 1994. He is currently a postdoctoral fellow at the Indian Institute of Science. Y. Arunkumar earned his M.E. in mechanical engineering from the Indian Institute of Science in 1993. He is currently a lecturer at Malnad Engineering College, India. P.V.J. Chetty earned his M.E. in metallurgical engineering from the Indian Institute of Science in 1993. He is currently manager of Mineral Pulverising Mills in India. K.S. Raman earned his Ph.D. in mechanical metallurgy from the Indian Institute of Science in 1970. He is currently a professor in the Department of Metallurgy at the Indian Institute of Science. K.S.S. Murthy earned his Ph.D. in foundry metallurgy from the Indian Institute of Science in 1969. He is currently a professor in the mechanical engineering department at the Indian Institute of Science.     

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.     

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.     

Producing lower-cost titanium for automotive applications

Although titanium has attractive properties that can improve the performance and economy of automobiles, at its current cost, it cannot compete with steel in most applications for which it is suited. It is readily apparent that titanium cannot be considered a viable mass-market automotive materials alternative as long as it is produced with the Kroll process. A look at existing and new technologies (as well as some that have been found lacking) in terms of applicability toward high-volume, low-cost titanium production for automotive applications indicates other options. A.D. Hartman earned his B.S. in chemical engineering at the South Dakota School of Mines and Technology in 1983. He is currently a chemical engineer in the Thermal Treatment Technologies Division at the Albany Research Center, Department of Energy. S.J. Gerdemann earned his B.S. in engineering science at the University of Virginia in 1976. He is currently a chemical engineer in the Thermal Treatment Technologies Division at the Albany Research Center, Department of Energy. Mr. Gerdemann is a member of TMS. J.S. Hansen earned his B.S. in metallurgical engineering at Oregon State University in 1972. He is currently a metallurgist in the Thermal Treatment Technologies Division at the Albany Research Center, Department of Energy. For more information, contact P.C. Turner, Albany Research Center, Department of Energy, 1450 S.W. Queen Avenue, Albany, Oregon 97321; 541-967-5863; fax 541-967-5958; e-mail turner@alrc.doe.gov.     

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.     

Additives and the corrosion resistance of aluminosilicate refractories in molten Al-5Mg

Additives such as BaSO₄, CaF₂, and AlF₃ have been used in aluminosilicate refractories to reduce the detrimental reactions (corrosion) occurring between molten aluminum alloys and these refractories. In this article, the effects of these additives and Na₂O on the behavior of a simple aluminosilicate ceramic in molten Al-5Mg are presented. Because these refractories usually contain several oxides in addition to aluminum and silica, the analysis of their corrosion behavior can be complicated or even inconclusive. Thus, only aluminosilicates with a mullite-like composition were selected for study. M. Allahevrdi earned his Ph.D. in materials engineering at McGill University in 1995. He is currently a postdoctoral associate at Rutgers University, Center for Ceramic Research. Dr. Allahevrdi is also a member of TMS. S. Afshar earned his Ph.D. in metallurgy at école des Mines de Saint-étienne, France, in 1986. He is currently a researcher at école Polytechnique de Montréal. C. Allaire earned his Ph.D. in metallurgy and materials science at école Polytechnique of Montréal in 1985. He is currently a professor at école Polytechnique of Montréal. Dr. Allaire is also a member of TMS.     

The direct metal deposition of H13 tool steel for 3-D components

The rapid prototyping process has reached the stage of rapid manufacturing via the direct metal deposition (DMD) technique. The DMD process is capable of producing three-dimensional components from many of the commercial alloys of choice. H13 tool steel is a difficult alloy for deposition due to residual stress accumulation from martensitic transformation; however, it is the material of choice for the die and tool industry. This article reviews the state of the art of DMD and describes the microstructure and mechanical properties of H13 alloy deposited by DMD. J. Mazumder earned his Ph.D. at Imperial College, London University. He is a professor at the University of Michigan. J. Choi earned his Ph.D. in mechanical engineering at the University of Illinois at Urbana-Champaign in 1994. He is currently a research fellow at the University of Michigan. K. Nagarathnam earned his Ph.D. in mechanical engineering at the University of Illinois at Urbana-Champaign in 1994. He is currently a research fellow at the University of Michigan. Dr. Nagarathnam is a member of TMS. Justin Koch earned his M.S. in mechanical engineering at the University of Illinois at Urbana-Champaign in 1985. He is currently a project engineer for Caterpillar. Daniel Hetzner earned his Ph.D. in metallurgical engineering at the University of Tennessee in 1980. He is currently a research specialist.     

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.     

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.     

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.     

The intelligent processing of materials: An overview and case study

The intelligent processing of materials is an emerging methodology for simulating and controlling the processing and manufacture of materials. It involves model-based process optimization, in-situ microstructure sensing, and the control of both the process variables and the performance-defining microstructural attributes of a material during its synthesis and processing. It is finding widespread application in the manufacture of electronic, photonic, and composite (i.e., high-performance) materials, as well as primary metals. Authors’ Note: This article is based on AGARD SMP lecture series 205, Smart Structures and Materials: Implications for Military Aircraft of New Generation, held in Philadelphia, Pennsylvania, on October 30–31, 1996; in Amsterdam, Netherlands, on November 18–19, 1996; and in Paris on November 21–22, 1996. Haydn N.G. Wadley earned his Ph.D. in physics at the University of Reading, England, in 1979. He is currently the Edgar A. Starke, Jr., research professor in materials science and associate dean for research at the School of Engineering and Applied Science at the University of Virginia. Dr. Wadley is a member of TMS. Ravi Vancheeswaran earned his Ph.D. in mechanical and aerospace engineering at the University of Virginia in 1996. He is currently a research assistant professor at the School of Engineering and Applied Science at the University of Virginia. Dr. Vancheeswaran is also a member of TMS.