Effects of Thermal Treatment on Microstructure and Mechanical Properties of Free Wrought AZ91 Magnesium Alloy

摘要

One-off isothermally free wrought forming of AZ91 Magnesium alloy from cuboids of 30 × 30 × 80 mm~3 to sheets of thickness of 5 mm at the temperature of 400℃ and initial strain rate of 1.0 s~(-1) were carried out followed after as-cast, solid solution for 4 hours at 415℃ and homogenization for 6 hours at 380℃, respectively. Static aging at 220℃ was followed by mechanical properties measurement. The experimental results show that no recrystallized microstructure but coarsely elongated original grains and Mg_(17)Al_(12) phase was found in sheet wrought by as-cast AZ91. However, solid solution before wrought led to refined microstructure duo to dynamic recrystallization (DRX), which improved mechanical properties. Homogenization before wrought also resulted in extra refined grains recrystallized between elongated Mg_(17)Al_(12) phase, which markedly improved mechanical properties and ageing response due to the cooperated strengthening role of refined DRX grains and Mg_(17)Al_(12) phase.