Tensile deformation behaviour of two aluminium alloys at elevated temperatures

The tensile deformation behaviour of two recently developed aluminium alloy s in the temperature range 200-550 degrees C is characterized in this paper . The aluminium alloys studied here are an automotive stamping grade Al-Mg- Mn alloy and an Al-Li-Cu alloy. Tensile properties at elevated temperatures were determined under different temperature-strain rate combinations. An a nalysis of deformation and fracture behaviour at elevated temperatures is a lso presented. The Al-Mg-Mn alloy and the Al-Li-Cu alloy exhibited extended ductility or mild superplasticity at elevated temperatures. Metallographic and fractographic studies revealed appreciable grain growth and cavitation at elevated temperatures. The fracture elongation of Al-Mg-Mn alloy decrea sed beyond 430 degrees C. Pronounced apparent strain hardening was observed in the case of the Al-Li-Cu alloy in the temperature range 525-550 degrees C at a very low strain rate. This could be due to dynamic grain growth and /or dislocation structure evolution.