Long-period stacking ordered phase kinking, twinning behavior and dynamic recrystallization of Mg-Gd-Y-Zn-Zr alloy under severe shear deformation

A novel severe shear specimen with a maximum shear strain of 3 was designed to further clarify kinking and fragment behavior of long period stacking ordered (LPSO) phases, as well as their interaction with twinning behavior and dynamic recrystallization (DRX) behavior under severe shear deformation (SSD). The results indicate that promoted kinking and fragment behavior for LPSO phases is obseved for hihger activation of basal dislocations induced by shear deformation. Besides the known crack causd by LPSO kinking, a new fragment process without kink bands formation is found for block-shaped LPSO phases under SSD, which follows three stages of micro-crack at the interface of LPSO/alpha-Mg matrix, crack and crush. Moreover, the actvition of tension twinning detected at kinked boundaries is reveled to be controlled by the combined effect of LPSO kinking and shear stress state. Specifically, crystal rotation related to LPSO kinking reorient grains to be possbile for twinning, and then high effective Schmid factor (ESF) under shear stress furter prioritise the twining acivaiton. Additionally, orientation dependence of DRX behaviors was weakened due to the particle-stimulated nucleation (PSN) mechanism caused by interdendritic block-shaped LPSO phases, which can accelerate the formation of low angle grain boundaries and DRX grains by activated pyramidal slip systems even at basal grains.