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.