Effect of pre-induced precipitations on microstructure evolution and the mechanical properties of pre-twinned ZK61 Mg alloys at elevated temperatures

Abstract

To examine the effects of pre-induced precipitations on microstructure evolution and mechanical properties of pre-twinned ZK61 Mg alloy at elevated temperatures, the commercially rolled ZK61 Mg alloy sheets (AR samples) were pre-twinned and {10−12} tensile twins were added (PT samples). Some samples were aged, precipitated phases were introduced (PTA samples), and subsequently uniaxial tensile strain was applied. The results reveal that at elevated temperatures, the interactions of detwinning, dynamic recrystallization (DRX), and precipitation have a distinctive impact on the microstructure evolution. At room temperature (RT) and 100 ℃, strain is dominated by detwinning, while the precipitation phase impedes the detwinning behaviors. DRX influences the evolution of the microstructure at 150 ℃, 200 ℃, and 250 ℃. The presence of precipitated phases promotes recrystallization nucleation. Continuous DRX (CDRX), detwinning, and precipitated phase deformation are coordinated at 150 ℃. DRX in aged samples has a limited effect, while detwinning plays a dominant role. The ultimate tensile strength (UTS) value increment of PTA sample relative to PT sample reaches 31.8 MPa. The deformation is generated by the discontinuous DRX (DDRX) at 250 ℃, and the precipitation and DDRX have a higher impediment on detwinning, resulting in more twins restraining in the PTA sample. The UTS value of PTA sample only increases by 7.7 MPa compared with PT sample.