Plastic deformation response during crack propagation in Mg bicrystals with twin boundaries

Abstract

The present study is committed to exploring the intergranular crack performance of magnesium (Mg) bicrystals with typical twin boundaries (TBs) by molecular dynamics simulations coupled with finite element method. Atomic modeling is conducted to determine the traction–separation (T–S) law in a cohesive zone. Importantly, the T–S curves together with microstructure evolutions are employed to investigate the plastic response during crack propagating. Afterwards, the obtained T–S parameters are embedded into cohesive elements along grain boundaries of polycrystalline structure, which is efficiently characterized by the Voronoi tessellation. As consequence, the simulation of intergranular fracture in Mg bicrystal is successfully realized by finite element analysis with failure criteria. Eventually, the critical stress intensity factors of compact tension specimens with various TBs are predicted availably. The results demonstrate that the crack propagation is strongly sensitive to twin boundary and resultant plastic deformation behavior at the crack tip. Moreover, it is found that microcracks are produced when TBs interact with dislocations. A comparison between simulated results and published experimental data is provided to highlight the reliability of the multiscale method for studying the cracking performance.