Microstructure Evolution in Al-Mg Alloys during and after Hot Deformation

Controlling the microstructure developed during hot rolling is of great importance to controlling final material properties. Changes in processing parameters and chemical composition alter the recovery-recrystallization-grain-growth processes that control microstructure evolution. To better understand these processes in two Al-Mg alloys, cylindrical specimens were subjected to hot compression at temperatures from 300 to 500°C with a fixed strain rate of 1.0 s−1. Upset specimens were immediately quenched by He gas to preserve their deformed microstructures. Specimen sections were then annealed to separate the dynamic and static components of microstructure evolution. Specimen microstructures were characterized by optical and electron microscopy. Grain size and the degree of recrystallization were measured as functions of specimen chemistry, compression-test conditions and annealing conditions. The experimental results are interpreted to better understand the mechanisms of microstructure evolution and to evaluate new paths to microstructure refinement during hot rolling.