Interaction between crack and grain boundary in magnesium

ZY Xing and HD Fan and GZ Kang, ENGINEERING FRACTURE MECHANICS, 275, 108866 (2022).

DOI: 10.1016/j.engfracmech.2022.108866

In polycrystalline materials, grain boundaries (GBs) play an important role in resisting crack growth. In this study, the interaction of a crack on basal plane with GBs in magnesium was investigated by molecular statics simulations. Three types of GBs with different mis-orientation angles were considered, i.e., 2110 asymmetric tilt GB, (0110) twist GB and 0001 asymmetric tilt GB. Simulation results show that, for 2110 asymmetric tilt GBs, the crack always penetrates through the GBs but the crack growth path in neighboring grain changes from (0001) basal plane to (0111) pyramidal plane as the tilt mis-orientation angle increases. For (0110) twist GBs, the crack propagation mechanism changes from trans-granular fracture into inter-granular fracture with the increasing twist mis-orientation angle. For 0001 asymmetric tilt GBs, trans- granular fracture happens at small and high tilt mis-orientation angles, while inter-granular fracture occurs at intermedium mis-orientation angles. The critical stress intensity factor (SIF) for crack propagation across or along GB is correlated with the corresponding GB energy. Trans-granular fracture occurs when the GB energy is low, and the critical SIF also increases with the increasing GB energy. For high energy GBs, inter-granular fracture occurs and the critical SIF changes hardly with the increasing GB energy. The current work provides insights into understanding the behavior of cracks and ductility enhancement in magnesium.

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