Structural and kinetic aspects of continuous grain coarsening in a fine-grained Al–0.3Sc alloy

A supersaturated Al–0.3 wt.% Sc alloy was produced by equal channel angular pressing to an equivalent von Mises strain of 9.2 then pre-aged at 350 °C to generate a starting grain size of 1 μm. The microstructure was highly resistant to grain coarsening at temperatures up to 500 °C with discontinuous coarsening only occurring after extended annealing. A detailed statistical analysis showed that the initial grain size distribution was very close to lognormal, and remained lognormal throughout annealing, with the normalized size distribution not affected by time and temperature despite a broadening of the distribution. The homogeneous evolution of the microstructure during annealing, coupled with no appreciable change in texture, is consistent with the advanced stages of continuous recrystallization, and also structurally and kinetically similar to conventional subgrain growth/grain growth in high-stacking fault energy, low-solute alloys.