Aluminum & Education: Reaching Out to Tomorrow's Engineers and Designers
Reprinted with permission from the Spring 2000 Aluminum Now magazine.
This continues a series on aluminum technology centers located at colleges and universities throughout the United States. The centers represent a partnership between the aluminum industry, academia and government agencies.
Our mission is to create knowledge and disseminate that knowledge," says Diran Apelian, Ph.D., director of the Metal Processing Institute at Worcester Polytechnic Institute in Massachusetts. "We are really a business, with customers and products. Like any business, we must build trust, relationships, credibility and good work."
The Metal Processing Institute (MPI) is comprised of four centers: the Aluminum Casting Research Laboratory, the Center for Heat Treating Excellence, the Powder Metallurgy Research Center and the Semisolid Metal Processing Center. With the exception of the Powder Metallurgy Research Center, each center conducts research and development (R&D) programs pertaining to aluminum. Approximately 80 percent of the work is done at MPI; the rest is outsourced to other universities and laboratories.
The Worcester Polytechnic Institute is essentially the "parent company" of the entire enterprise. It has forged partnerships with all segments of the aluminum industry. Primary and secondary producers, suppliers, equipment manufacturers, product manufacturers and processors and end users have joined the institute to form center consortiums.
Much of the institute's research centers on "advancing the state of the art in near-net-shape manufacturing," or as Apelian asks, "How do you make a component close to its final shape?" Each research center conducts steering committee projects, proprietary projects sponsored by individual companies, and precompetitive fundamental research funded by the institute's 130 corporate members. A center may also conduct basic research, funded by the federal government, pertaining to emerging technologies that may prove useful to its particular subject area.
Aluminum Casting Research Laboratory
Founded in 1984, the Aluminum Casting Research Laboratory was actually established at Drexel University. Apelian was on the faculty of that Philadelphia institution when he and his colleagues were approached to establish the center by Ray H. Witt, president of CMI International (now Hayes-Lemmerz) and other industry leaders. The center moved to Worcester with Apelian in the late 1980s.
One of the center's current programs concerns the interactions between porosity and fatigue performance in aluminum castings. Aluminum cast alloys, specifically aluminum-silicon-magnesium alloys, are being increasingly used in automotive applications. Their excellent castability, corrosion resistance and high strength-to-weight ratio make them ideal for this application, yet they can be prone to porosity formation, or microscopic gas pockets caused by the alloys' susceptibility to excessive hydrogen uptake and shrinkage.
This program was established to understand the relationship between porosity and fatigue fracture resistance. Apelian likens the relationship during casting to tension and compression. If any object is pulled (tension) and pushed (compression) beyond its capacity, it will break. The same holds true for castings with excessive porosity. Those pores can make the alloys vulnerable to fatigue fractures following the casting process. Among the program's goals is to reduce porosity by controlling the hydrogen content in the melt and changing the mold temperature. "The dynamic properties of cast aluminum components is a critical area, and one which requires much fundamental work," Apelian emphasizes. "The structural features and the distribution, shape and size of permissible defects in cast components need to be established to expand the use of castings for high-integrity, net-shaped applications."
"The Aluminum Casting Research Laboratory's success is founded in its close, direct ties with industry and its exceptional understanding of industrial needs," says John Jorstad, the center's director-at-large and president of Formcast Inc., the leading producer of non-automotive semisolid engineered components. "The aluminum foundry industry depends on technology centers like this for R&D that individual companies simply could not afford to do alone."
Center for Heat Treating Excellence
Seventy corporate members participate in the Center for Heat Treating Excellence, which was founded last year. Established in 1999, the center is an alliance between the industrial sector and university researchers to collaboratively address the heat-treating industry's short- and long-term needs. The center's intent is to enhance the industry's position by applying fundamental research to solve industrial problems and advance heat-treatment technology.
The center is pursuing several projects. Two are being investigated by the WPI team. The first concerns quenching, the method of arresting the heat-treating process. The WPI team is studying the entire field of quench media, as well as controlling the quenching process. The second project addresses predictive tool development for part temperature control during the complex loading of furnaces. At the Illinois Institute of Technology in Chicago, a team is studying the control of residual stresses and distortion. And at the University of Connecticut, Hal Brody and John Morrall are studying the heat treatment of cast and wrought aluminum alloys.
In general, heat treating is the process by which an aluminum alloy is elevated to a high temperature, thereby changing its microstructure to improve performance. Apelian uses cooking as a metaphor in explaining the evolution of microstructure-property relationships during processing. The temperature at which an omelette is cooked will influence the resultant property--the taste of the end product. Similarly, through thermal treatment, the resultant properties and performance of a component can be manipulated.
The center has the full support of both ASM International (the industry's professional association) and the Materials Technology Institute of the Chemical Process Industries. In addition, the center has established a relationship with the national laboratories, most notably Oak Ridge National Laboratory.
Semisolid Metal Processing Center
Semisolid metal processing involves working with metal that is not completely solidified. The processing of materials in the semisolid state is a relatively new technology that offers distinct advantages over the near-net-shape manufacturing processes.
This process is ideally suited for die casting. In fact, a number of automotive components are currently produced using semisolid metal technologies. The raw material is melted, then allowed to cool and solidify. The dendrites (branching, tree-like figures within the material) formed during solidification are broken up, and their shape is changed using mechanical forces. The material then has a microstructure made up of round, rosette-like crystals. The process is called "rheocasting."
A major benefit to the die-casting industry is that the rheocast ingot has significantly lower viscosity than the solid counterpart. This is important because upon heating the rheocast ingot to the two-phase region (50 percent solid and 50 percent liquid temperature), the semisolid material flows easily into the die. In essence, the semisolid material exhibits both solid-like and liquid-like behaviors. As a "solid," the material maintains its structural integrity. Therefore, during processing it is handled like a solid. As a "liquid," the material flows with relative ease and fill the die cavities well.
The center's goal is to produce a concentrated effort toward achieving a better understanding of fundamental issues concerning semisolids. The laboratory addresses issues related to increased yield and improved quality through consistent microstructure control. The ultimate objectives are to improve the knowledge base of semisolid technologies and to realize the process' full potential.
Earning the Industry's Trust
Apelian stresses the importance of nurturing the relationships he has established over the last 30 years. "We are committed to the industry and the educational mission of the industry," he says. But he cautions that the partnership between industry, academia and government requires commitment and a great deal of hard work. "You have to earn credibility. You have to earn trust. You have to earn them almost on a daily basis."
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