The role of crystal orientation in cracking performance of HCP magnesium single crystals

Abstract

This work was committed to conducting atomistic simulations for exploring the crystal orientation dependence of fracture behavior in hexagonal close-packed (HCP) magnesium single crystals. Combined with the traction–separation (T–S) law of the cohesive zone model, microstructure evolutions with various orientations during crack propagation were investigated to probe the anisotropy of crack pattern. We discovered that stress concentrations at the crack tip led to dislocation emission, which was strongly dependent upon the Schmid factor. It was also found that for the (1_210) [10_10] crack orientation, the stress-induced phase transition occurring at the crack tip delayed the crack extension, indicative of the coupling between phase transition and crack propagation. Interestingly, there were several deformation twin types produced at various orientations, which duly affected the crack pattern. Especially for the (0001) [1_210] crack orientation, the formation and growth of {11_21} twins promoted the brittle-to-ductile cracking, which was different from other two orientations. Furthermore, the resultant T–S parameters together with microstructural evolution information revealed the contribution of crystal orientation to intrinsic fracture behavior. This study is expected to offer in-depth insights on the crack-tip behavior induced by crystal orientation, promoting the development of magnesium.