Damage evolution of extruded magnesium alloy from deformation twinning and dislocation slipping in uniaxial stress-controlled low cycle fatigue

The damage evolution of an extruded AZ31 magnesium alloy in uniaxial stress-controlled low cycle fatigue is investigated using a quasi -in-situ method. In the three studied samples, that is, slipping dominated (SD), twin-ning/detwinning/basal slipping (TDBS), and twinning/detwinning/slipping (TDS), the fractions of slip bands and/or twins keep increasing till a critical cyclic number, and are essentially unchanged in the subsequent cycles. Inter-granular micro-crack initiation is found to be favorable in the TDS and SD samples. While both the inter -granular and intra-granular micro-cracks are detected in the TDBS sample. Moreover, the non-Schmid behavior in the crack trans-granular propagation path is investigated.