Molecular dynamics simulation of the orientation and temperature dependence in MgAl2O4 spinel

Through molecular dynamics simulations, this study investigates the orientation and temperature dependence of the tensile mechanical properties, the failure mechanism, and crack propagation characteristics of MgAl2O4 single crystal. The results reveal significant anisotropy and temperature sensitivity in the mechanical properties of MgAl2O4. Particularly, [111]-oriented MgAl2O4 exhibits the highest elastic modulus and ultimate tensile strength but a relatively minor failure strain. In the 300 K to 2100 K temperature range, the elastic modulus, ultimate tensile strength, and failure strain decrease with increasing temperature. At 2100 K, MgAl2O4 exhibits excellent structural stability and high-temperature strength. The failure mechanism is a brittle fracture initiated by the continuous convergence of vacancies into micropores/microcracks. The propagation of microcracks is influenced by crystal orientation and slip bands. Nevertheless, high temperatures significantly accelerate crack propagation, leading to premature failure. This study provides guidelines for preparing MgAl2O4 with excellent mechanical properties.