Superplastic Behavior of Copper-Modified 5083 Aluminum Alloy

An AA5083 aluminum alloy was modified with two different levels of Cu additions, cast by direct-chill method, and thermo-mechanically processed to sheet gauge. Copper additions 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 the finest grain size 5.3 μm, a peak strain-rate sensitivity of 0.6 at a strain-rate of 1 × 10⁻² s⁻¹, and tensile elongation values between 259 and 584% over the temperature range, 400-525 °C, and the strain rate range, 5 × 10⁻⁴ to 1 × 10⁻² s⁻¹, investigated. In biaxial pan forming tests, only the Cu-containing alloys successfully formed pans at the higher strain rate 10⁻² s⁻¹. The high-Cu alloy showed the least die-entry thinning. Comparison of ambient temperature mechanical properties in O-temper state showed the high-Cu alloy to have significantly higher yield strength, ultimate strength, and ductility compared to the base 5083 alloy.