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.     

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.     

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 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.     

Dendrite fragmentation and the effects of fluid flow in castings

In the absence of grain-refining additions to a melt or of any significant heterogeneous nuclei, equiaxed grains can only originate in a casting from primary dendrite fragments. Thus, it is pertinent to understand how dendrites become fragmented and to explain why liquid stirring should appear to “break up” and refine the grain structure. Dendrite fragmentation occurs by local remelting, and fluid flow is important as a dispersal mechanism. A. Hellawell earned his D.Phil. in physical science at Oxford University in 1956. He is currently emeritus research professor at Michigan Technological University. He is also a member of TMS. S. Liu earned his M.S. in materials science and engineering at Northwestern Polytechnical University, China, in 1989. He is currently a Ph.D. candidate at Michigan Technological University. S.Z. Lu earned his Ph.D. in metallurgical engineering at Michigan Technological University in 1986. He is currently a research associate professor at Michigan Technological University. He is also a member of TMS.     

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.     

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.     

Simulating convection and macrosegregation in superalloys

Numerical simulations using a mathematical model of the dendritic solidification of multicomponent alloys that includes thermosolutal convection and macrosegregation were conducted on nickel-based alloys. The results show that segregation patterns vary greatly with cooling conditions, adopting several shapes and levels of intensity. In addition, the segregation patterns are particularly sensitive to the values of the equilibrium partition coefficients of the alloy components. S.D. Felicelli earned his Ph.D. in mechanical engineering from the University of Arizona in 1991. He is currently a research scientist at Centro Atomico Bariloche, Argentine Atomic Energy Commission. D.R. Poirier earned his Sc.D. in metallurgy from the Massachusetts Institute of Technology in 1966. He is currently professor of materials science and engineering at the University of Arizona. Dr. Poirier is a member of TMS. A.F. Giamei earned his Ph.D. from Northwestern University in 1967. He is currently principal scientist in the Materials and Structures Technology Department of the United Technologies Research Center. Dr. Giamei is also a member of TMS. J.C. Heinrich earned his Ph.D. in mathematics fromthe University of Pittsburgh in 1975. He is currently professor of aerospace and mechanical engineering at the University of Arizona.     

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.     

A strength evaluation of SiC fibers prepared by RFCVD

Large-diameter SiC fibers have been prepared using chemical vapor deposition by radio-frequency heating; this article focuses on the evolution of fiber strength in the preparatory and secondary treatment stages of this preparation. Fibers that are produced by this process show high tensile strength (>3,500 MPa) for various gauge lengths. Furthermore, these fibers exhibit good strength retention capability during a wide range of high temperatures. In keeping with the goal to develop cost-effective metal/resin matrix composites of high quality using such fibers, a substantial amount of work on surface modification has been carried out, and, in fact, also dominates the direction of radio-frequency chemical vapor deposition-SiC fibers developments. Y. Du earned his M.S. in physical metallurgy at Dalian University of Technology in 1990. He is currently an assistant professor at the Institute of Metal Research, Chinese Academy of Sciences. Mr. Du is a member of TMS. X. Chang earned his B.S. in powder metallurgy at Southcentral Polytechnic University in 1988. He is currently a research assistant professor in the State Key Laboratory for RSA, Institute of Metal Research. N. Shi earned his B.S. in physical chemistry at Northeastern University in 1966. He is currently a research professor in the Special Ceramic Laboratory, Institute of Metal Research. J.C.Y. Chung earned his Ph.D. in materials engineering at Hong Kong University in 1992. He is currently an assistant professor at the City University of Hong Kong. K.P. Rao earned his Ph.D. in metallurgical engineering at the Indian Institute of Technology, Madrid, in 1983. He is currently an associate professor at the City University of Hong Kong.     

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 effect of hot isostatic pressing on cast aluminum

Aluminum-silicon alloys are the most important commercial aluminum casting alloys, primarily because of their superior casting characteristics. This article discusses the effect of hot isostatic pressing on the mechanical properties of cast aluminum alloy A356. The effect of low-cost Densal hotisostatic pressing is also examined. C.S.C. Lei earned his Ph.D. in mechanical engineering/solid mechanics at Drexel University in 1987. He is currently a visiting scientist at the Naval Air Warfare Center, Aircraft Division. W.E. Frazier earned his Ph.D. in materials engineering at Drexel University in 1987. He is currently the head of metal, ceramics, and nondestructive evaluation at Naval Air Warfare Center, Aircraft Division. Dr. Frazier is also a member of TMS. E.W. Lee earned his Ph.D. in materials engineering at the Georgia Institute of Technology in 1982. He is currently propulsion materials team leader at Naval Air Warfare Center, Aircraft Division.     

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.     

Controlling remelting processes for superalloys and aerospace Ti alloys

Remelting is performed to facilitate the production of clean, fully dense, homogeneous castings of superalloys and aerospace titanium alloys and is crucial to the defect-free production of these important materials. Modern electroslag remelting and vacuum arc remelting control systems are closed-loop, single input-single output systems that oversimplify the physical properties of the processes; the ever-increasing demand for cleaner, more highly engineered, chemically tuned alloys has pushed these control methodologies to their limit. A new generation of these controllers is being developed by the Specialty Metals Process Consortium and Sandia National Laboratories to answer the challenges of remelting control for the next generation of alloys; these control systems will use multiple sensor inputs and apply material-specific system and process models. D.K. Melgaard earned his Ph.D. in computer science at Kansas State University in 1976. He is currently a member of the technical staff at Sandia National Laboratories. R.L. Williamson earned his Ph.D. in chemistry at the University of Washington in 1983. He is currently a principal member of the technical staff at Sandia National Laboratories. Dr. Williamson is also a member of TMS. J.J. Beaman earned his Sc.D. in mechanical engineering at Massachusetts Institute of Technology in 1979. He is currently the Andersen professor in manufacturing systems engineering at the University of Texas.     

The high-quality precision casting of titanium alloys

A technique for the high-quality precision casting of titanium alloys has been developed that consists of the instantaneous dissociation of oxide at the metal-mold interface, followed by the rapid absorption and diffusion of the dissociated oxygen into the subsurface of the cast parts during solidification and cooling. In centrifugal casting trials using less molten alloy than required to completely fill the mold, the results suggest that the melt flowing in the mold cavities maintains contact with the vertical inside walls and directionally solidifies from the far end of the cavity to the gate, corresponding to the gradient in the centrifugal force on the horizontal plane. This force enhances the removal of defects, such as entrapped gas bubbles and solidification shrinkage. The results have enabled the development of a two-dimensional model to simulate melt flow during centrifugal casting. Author’s Note: Unless otherwise indicated, compositions are given in weight percent. Ken-ichiro Suzuki earned his Ph.D. at Tohoku University, Faculty of Engineering. He is currently a visiting professor at the Graduate School of Iron and Steel Technology at Pohang University of Science and Technology.     

Deformation mechanisms and tensile superplasticity in nanocrystalline materials

Nanocrystalline materials provide a unique opportunity to investigate deformation mechanisms at an extremely fine microstructural scale. An intriguing question has been whether the deformation mechanisms scale with grain size to the nanocrystalline range or whether there are fundamental changes/transitions. The observations of low-temperature and high-strain-rate superplasticity in nanocrystalline materials with some unique features open up new possibilities for scientific and technological advancements. R.S. Mishra earned his Ph.D. in metallurgy at the University of Sheffield in 1988. He is currently adjunct assistant professor at the University of California at Davis. Dr. Mishra is also a member of TMS. S.X. McFadden earned his B.S. in materials engineering at California Polytechnic State University, San Luis Obispo, in 1996. He is currently a research associate at the University of California at Davis. Mr. McFadden is also a member of TMS. R.Z. Valiev earned his Dr.Sci. in solid-state physics from the Institute for Materials Science, Academy of Sciences of the USSR, Kiev, in 1984. He is currently the scientific director and professor at the Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Russia. Dr. Valiev is also a member of TMS. A.K. Mukherjee earned his D. Phil. in materials science at Oxford University in 1962. He is currently a professor of materials science at the University of California at Davis. Dr. Mukherjee is also a member of TMS.     

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.     

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.     

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.     

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.