Intergranular Fracture Behaviour of ZK60 Magnesium Alloy Sheet by Combined CPFE-CZM and In-Situ SEM Method

Magnesium alloy has the superiority of low density, excellent machinability and admirable dimensional stability, however, cause by it has the closely-arranged hexagonal crystal structure, there are a small amount independent slip systems at room temperature, that means poor plastic deformation ability. This investigation revealed the plastic deformation and fracture characteristics of magnesium alloy sheets by procedures of crystal plasticity (CP) and in-situ SEM experiments. The influence of the occurrence of the second-phase particles, grain boundaries distribution on the grain boundary cracks and grain boundaries damage on the microstructure morphology was analyzed by the observation and simulation. Results demonstrate that the damage evolution regulation along grain boundary of ZK60 magnesium alloy was verified by using investigation during plastic deformation, and the generation and propagation of microcracks on grain boundaries showed little difference with the experiments results. The presence of the second-phase particles is more likely to motivate the initiation of cracks at the grain boundary, which enables it easily to originate grain boundary fracture, and the crack predominantly distributes at the junction of grain boundaries or multiple grain boundaries. The final overall fracture is both related to the influence of local large cracks and the damage accumulation of the whole fracture path. Regulating the local damage distribution is beneficial to coordinating the overall damage. This study deepens the understanding of intergranular fracture, mechanical response and microstructure evolution of ZK60 magnesium alloy sheets during tensile deformation at room temperature.