Mechanical properties and deformation mechanism of AZ31B joints under cryogenic temperature and high strain rate loading

The microstructure and texture of many Mg alloys prepared by friction stir welding (FSW) have been investigated with associated to mechanical properties. However, the microstructure evolution and its correlation with mechanical properties are rarely studied in cryogenic temperature and high strain rate loading. In this work, the microstructure and mechanical behavior of Mg alloy joints, AZ31B, were investigated. The findings unveiled that the decrease of loading temperature promoted the compress twin activation, accompanied by an increase in ultimate strength and a slightly decrease in plasticity. The enhanced of ultimate tensile strength (about 60 MPa) from 25°C to −50°C is ascribed to twin-twin interactions and increased amount of compression twin({10-11}and{10-13}). The decrease of plasticity (about 4.5%) is associated to the stress concentration, due to the dislocation thermal activation is suppressed.