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ORNL optimizes process to produce more consistent aluminum casting
OAK RIDGE, Tenn.,
March 4, 1997
Researchers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) have worked with Thompson Aluminum Casting Company (TAC) of Cleveland, Ohio, as part of a cooperative research and development agreement (CRADA) to optimize a process to produce a sounder and more failure-resistant aluminum component.
The project, funded by the Heavy Vehicle Technology program in DOE's Office of Transportation Technology, is aimed at enabling the wider use of lightweight materials in the transportation sector to reduce energy consumption in the form of fuel. It allows for the construction of a stronger engine mount in vehicles.
The fact that a cast aluminum part can have defects in the form of small cavities so concerned TAC that the company sought to develop a process called metal compression forming, a variant of the squeeze casting process, that could produce parts with fewer cavities reliably and consistently. In order to optimize the process to produce commercial components and to meet the cost and performance specifications of the transportation industry, Thompson teamed with ORNL researchers to take advantage of the computer modeling and simulation expertise not available in-house. The result of this unique collaboration is a metal forming process that not only produces a more consistent and sound aluminum part, but one that is more resistant to cracking that can be caused by service stress.
In some applications, aluminum components produced by this process will replace cast iron or steel components resulting in a substantial weight savings per vehicle. In other cases, substitution for more costly forged aluminum parts will provide an economic incentive for increased use of aluminum components.
"This development will enable parts suppliers to provide lower cost, lighter weight components to vehicle manufacturers, thereby improving the fuel economy of trucks and cars and reducing U.S. dependence on imported fuels," said James Eberhardt, director of DOE's Office of Heavy Vehicle Technologies. "The results of this project are an excellent example of what can be accomplished by such industry/government partnerships, each doing what it does best to achieve the project's goals."
The CRADA team headed by Srinath Viswanathan, a researcher in the Materials Processing Group of ORNL's Metals and Ceramics Division, used computer models of the casting process to find ways of pouring aluminum into the mold more smoothly and with fewer impurities.
"In this process, the metal flows slowly and the mold is not being filled at high pressure that often causes turbulence in the liquid metal, thus trapping gases and creating undesirable cavities in the final part," Viswanathan said. "In addition, the metal compression forming process uniquely allows for uniform pressure to be applied over the entire part, virtually squeezing out porosity that would normally be present."
In addition to developing the process for aluminum alloys, TAC and ORNL researchers, with continuing DOE funding, will be working to apply the process to a metal matrix composite alloy that would produce a stiffer component for other critical applications. Continued characterization and optimization of the process is expected to lead to much wider industrial application of the process in many non-transportation-related sectors.
This presents another often overlooked advantage of such research and development - a new material or process developed for one focused application that is found to possess more general applicability, thus expanding the usefulness and ultimate value of the original research project.
ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Research Corp.