Statistical aspects of grain coarsening in a fine grained Al-Sc alloy

A supersaturated Al-0.3 wt.% Sc alloy was cold deformed by ECAP to an equivalent von Mises strain of 9.2 then pre-aged at 350 degrees C to generate a fine-grained alloy with an average grain size of 1 mu m. The rnicrostructure was highly resistant to grain coarsening at temperatures up to 500 degrees C with a detailed statistical analysis showing that the initial grain size distribution was very close to lognormal and, throughout annealing, remained lognormal and the normalized frequency distribution was time/temperature invariant despite a moderate broadening of the size distribution. This behaviour is largely similar to subgrain coarsening during recovery and grain growth after recrystallization. The homogeneous evolution of the microstructure during annealing, coupled with no appreciable change in texture, is also consistent with the advanced stages of continuous recrystallization.