Effect of pre-aging treatment on microstructure and mechanical properties of hot compressed Mg–9Al–1Zn alloy

Hot compression tests were performed on the as-cast and aged Mg–9Al–1Zn (AZ91) alloy specimens at temperature of 300 °C to investigate the influence of pre-aging treatment on microstructure and mechanical properties of the hot compressed AZ91 alloy. The results show that the pre-aging treatment can be effective in increasing the precipitation number of Mg17Al12 phase and enlarging the discontinuous precipitates area, in which the dynamic recrystallization (DRX) occurs with discontinuous precipitates pinning at the newly-DRXed grain boundaries, leading the DRX ratio and (0 0 0 1) 〈1 1 2¯ 0〉 basal slip Schmid factor of the compressed specimens being increased. Both the ultimate tensile strength (UTS) and elongation to failure are higher in the age-compressed specimens. After compression at 300 °C and a strain rate of 0.2 s−1 with a compression ratio of 50%, UTS of the age-compressed specimen (336 MPa) is 44 MPa higher than that of cast-compressed specimen (292 MPa), and elongation to failure of the age-compressed specimen (9.8%) is three times as that of cast-compressed specimen (3.3%).