The Plastic Deformation Mechanisms of hcp Single Crystals with Different Orientations: Molecular Dynamics Simulations

The deformation mechanisms of Mg, Zr, and Ti single crystals with different orientations are systematically studied by using molecular dynamics simulations. The affecting factors for the plasticity of hexagonal close-packed (hcp) metals are investigated. The results show that the basal dislocation, prismatic dislocation, and pyramidal dislocation are activated in Mg, Zr, and Ti single crystals. The prior slip system is determined by the combined effect of the Schmid factor and the critical resolved shear stresses (CRSS). Twinning plays a crucial role during plastic deformation since basal and prismatic slips are limited. The 101 over bar 2 twinning is popularly observed in Mg, Zr, and Ti due to its low CRSS. The {10 (1) over bar1} twin appears in Mg and Ti, but not in Zr because of the high CRSS. The stress-induced hcp-fcc phase transformation occurs in Ti, which is achieved by successive glide of Shockley partial dislocations on basal planes. More types of plastic deformation mechanisms (including the cross-slip, double twins, and hcp-fcc phase transformation) are activated in Ti than in Mg and Zr. Multiple deformation mechanisms coordinate with each other, resulting in the higher strength and good ductility of Ti. The simulation results agree well with the related experimental observation.

Automated summary

The deformation mechanisms of Mg, Zr, and Ti single crystals with different orientations have been studied using molecular dynamics simulations, revealing that twinning plays a crucial role in plastic deformation, especially in Ti where multiple deformation mechanisms are activated. The results show that the activation of basal, prismatic, and pyramidal dislocations are influenced by factors like the Schmid factor and critical resolved shear stresses (CRSS), which vary among the different materials studied.