Size effect on mechanical properties of nanotwinned Mg2Si from molecular dynamics simulation

W Li and XL Zhang and B Duan and B Huang and M Huang and GD Li and PC Zhai, COMPUTATIONAL MATERIALS SCIENCE, 185, 109972 (2020).

DOI: 10.1016/j.commatsci.2020.109972

The excellent thermoelectric and mechanical properties of thermoelectric materials are the important guarantee for their industrial application. The introduction of twin boundary is an effective way to improve the thermoelectric properties of thermoelectric materials. However, our previous work shows the twin boundary weakens the mechanical properties of Mg2Si, and the role of twin size on mechanical properties remains unexplored so far. To determine the size effect of nanotwins on mechanical properties of Mg2Si, we applied molecular dynamics simulation to investigate the shear stress responses of nanotwinned Mg2Si with different sizes under the shear loading along its most plausible slip system (1-1-1)/<1 1-2>. The results show that the shear modulus and model size of nanotwinned Mg2Si increase and approach to the value of single crystal Mg2Si with the increasing twin size. While the ultimate strength does not change significantly with the increasing twin size. Under pure shear loading, the Mg-Si bond at the twin boundary breaks, leading to the failure of nanotwinned Mg2Si. The twin size has little influence on the failure of nanotwinned Mg2Si. Furthermore, the material failure mechanism and the weakening effect of temperature on materials are also discussed.

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