R. Verma, S. Kim, General Motors, Warren, MI

Summary:

A 5083-aluminum alloy was modified with two different levels of copper additions, cast by direct-chill method, and thermo-mechanically processed to sheet gauge. Copper addition reduced sheet grain size, decreased tensile flow stress and significantly increased tensile elongation under most elevated temperature test conditions. The high-Cu (0.8 Wt.%) alloy had a grain size of 5.3 µm, a peak strain-rate sensitivity of 0.6 at a strain-rate of 1x10^-2 s^-1, and tensile elongation values between 336 and 584% over most of the temperature range, 400-525°C, and the strain rate range, 5x10^-4 - 1x10^-2 s^-1, investigated. In biaxial pan forming tests, only the copper-containing alloys successfully formed pans at the higher strain rate of 10^-2 s^-1. The high-Cu alloy showed the least die-entry thinning. Ambient temperature mechanical properties of the high-Cu alloy were compared with those of the commercial SPF alloy SKY 5083. The high-Cu alloy had significantly higher YS, UTS and ductility in both the pre- and the post-form conditions.