Hot deformation and dynamic recrystallization in Al-Mg-Si alloy

The hot deformation behavior of Al-Mg-Si alloys was investigated by isothermal compression tests in a temperature range from 400 °C to 550 °C and a strain rate range from 0.001 to 1 s−1 with a true strain of 1.2. Flow behaviors were investigated and processing map was established. The microstructure of deformed samples was characterized by electron back scattered diffraction (EBSD) techniques. Geometrically necessary dislocation (GND) density and grain orientation spread (GOS) maps were calculated in order to investigate the dynamic recrystallization (DRX) mechanisms. It was found that the deformed microstructure strongly depends on the Zener-Hollomon (Z) values. Both sub-grain size and DRX fraction increased with decreasing ln Z. Both dynamic recovery (DRV) and DRX happened during deformation at elevated temperatures. DRV dominated at high ln Z, while DRX dominated at low ln Z. Three different DRX mechanisms, continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and geometric dynamic recrystallization (GDRX) were observed in the experimental materials. The main DRX mechanism depended on ln Z, i.e., GDRX dominated at low ln Z, CDRX dominated at middle ln Z, while DDRX dominated at high ln Z. •The microstructure depended on the Zener Holloman value upon hot deformation.•DRV dominated at high ln Z and DRX dominated at low ln Z.•DDRX, CDRX and GDRX dominated at high, middle and low ln Z, respectively.•Both subgrain size and DRX fraction increased with decreasing ln Z.