Molecular dynamics simulations of the effects of nanopores on mechanical behavior in the Mg2Sn system

M Huang and XQ Yang and G Chen and GD Li and PC Zhai, COMPUTATIONAL MATERIALS SCIENCE, 161, 177-189 (2019).

DOI: 10.1016/j.commatsci.2019.01.043

Binary compound Mg2Sn has received close attention for the thermoelectric energy conversion application, due to the abundance of constituent elements and the non-toxicity in the working condition. The introduction of nano-scale pores into crystalline Mg2Sn can significantly reduce the lattice thermal conductivity, while the nanopores might weaken the mechanical properties that are important for the commercial applications of Mg2Sn. To determine the effect of nanopores on mechanical behavior of Mg2Sn, we investigate the stress responses of tensile and shear deformations in uniformly and randomly distributed nanoporous bulks by using molecular dynamics (MD) simulations. We find that nanopores reduce the mechanical properties such as ultimate stress, fracture strain and elastic modulus of crystalline Mg2Sn. Furthermore, mechanical properties of randomly distributed nanoporous Mg2Sn are poorer than those of uniformly distributed nanoporous Mg2Sn. Nanopores lead to a reduction both in ultimate stress and elastic modulus. Meanwhile, the strength and the stiffness are closed related to porosity rather than radius of pores. In the case of tensile loading, the crack of (0 0 1)/<1 1 0> tilt orientations in the vicinity of nanopores results in zigzag breakage surfaces. As for shear loading, the atomic concentration, pore coalescence and shear band explore the fracture mechanism. Our results provide new perspectives of failure mechanism of nanoporous Mg2Sn under different loading methods.

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