The automotive industry is continuously investigating ways to reduce the mass of high volume production vehicles to improve fuel economy without compromising cost, styling or performance. In order to achieve this objective automakers have implemented high production volume superplastic forming (SPF) of aluminum sheet for certain components. Typically, the automakers have used the 5083 aluminum alloy for SPF because it is a relatively low-cost solid solution strengthened alloy where maximum strengths are achieved without a costly solution heat treatment and age process that often results in part distortion and re-strike. However, the 5083 alloy is limited to 150 MPa in yield strength and in order to further decrease vehicle mass a low-cost high strength superplastically formable alloy is required. This paper will discuss the strategy used to design and select an alternate alloy that can achieve strengths greater than 5083 while meeting the constraints of the automotive SPF process. Progress in the development of the new alloy for superplasticity will be reported including microstructural characterization, post SPF strength levels and high temperature tensile test results.
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