HOT DUCTILITY OF AN AL-4WT-PERCENT-MG-0.5WT-PERCENT-CU ALLOY

The hot formability of an experimental Al-4wt.%Mg-0.5wt.%Cu alloy has been studied by means of hot torsion testing. The corresponding micros tructures have been evaluated using optical and transmission electron microscopy (TEM). It has been found that the addition of 0.5 wt.% Cu t o a commercial AA5182 alloy reduces the alloy's hot formability. It de creases the inherent ductility, shifts the ductility loss point toward s a lower temperature and has a negative influence on the strain rate sensitivity of the ductility. Based on microstructural investigations, it was concluded that the decrease in ductility is related to a decre ase in the size of the Mn-bearing dispersoids, which retards recrystal lization. A modified preheating has been tested. It successfully incre ases the dispersoid size and improves the hot ductility of the Cu-bear ing alloy.