An investigation of microstructural stability in an Al-Mg alloy with submicrometer grain size

The microstructural stability of an Al-3%Mg solid solution alloy with a submicrometer-grained (SMG) structure (similar to 0.2 mu m) was evaluated using both static annealing and transmission electron microscopy over a range of temperatures from 443 to 803 K and differential scanning calorimetry (DSC) up to 773 K. The results show that the SMG structure contains many non-equilibrium grain boundaries but recrystallization occurs at the higher temperatures giving large grains with boundaries having high-angle equilibrium configurations. There are significant differences between the DSC curves of the SMG alloy and a standard cold-rolled Al-3%Mg alloy, due primarily to the advent of significant heat release at low temperatures in the SMG alloy because of recovery at the non-equilibrium grain boundaries. A temperature of similar to 500 K, close to half the absolute melting temperature, represents an effective upper limit for utilization of the SMG structure in this material. Copyright (C) 1996 Acta Metallurgica Inc.