Unveiling the mechanical response and accommodation mechanism of pre-rolled AZ31 magnesium alloy under high-speed impact loading

Split Hopkinson pressure bar (SHPB) tests were conducted on pre-rolled AZ31 magnesium alloy at 150-350 degrees C with strain rates of 2150s(-1), 3430s(-1) and 4160s(-1). The mechanical response, microstructural evolution and accommodation mechanism of the pre-rolled AZ31 magnesium alloy under high-speed impact loading were investigated. The twin and shear band are prevailing at low temperature, and the coexistence of twins and recrystallized grains is the dominant microstructure at medium temperature, while at high temperature, dynamic recrystallization (DRX) is almost complete. The increment of temperature reduces the critical condition difference between twinning and DRX, and the recrystallized temperature decreases with increasing strain rate. The mechanical response is related to the competition among the shear band strengthen, the twin strengthen and the fine grain strengthen and determined by the prevailing grain structure. The fine grain strengthen could compensate soften caused by the temperature increase and the reduction of twin and shear band. During high-speed deformation, different twin variants, introduced by pre-rolling, induce different deformation mechanism to accommodate plastic deformation and are in favor for non-basal slip. At low temperature, the high-speed deformation is achieved by twinning, dislocation slip and the following deformation shear band at different deformation stages. At high temperature, the high-speed deformation is realized by twinning and dislocation slip of early deformation stage, transition shear band of medium deformation stage and DRX of final deformation stage. (C) 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

Automated summary

Split Hopkinson pressure bar (SHPB) tests were conducted to investigate the mechanical response, microstructural evolution, and accommodation mechanism of pre-rolled AZ31 magnesium alloy under high-speed impact loading. The results showed that twin and shear band deformation were predominant at low temperatures, whereas a combination of twins and recrystallized grains dominated at medium temperatures, and dynamic recrystallization (DRX) was almost complete at high temperatures. The competition among shear band strengthening, twin strengthening, and fine grain strengthening determined the mechanical response, which was influenced by the prevailing grain structure. Different deformation mechanisms, including twinning, dislocation slip, shear band formation, and DRX, were observed at different deformation stages and temperatures.