Theoretical investigations on mechanical and dynamical properties of MAlB (M = Mo, W) nanolaminated borides at ground-states and elevated temperatures

Layered ternary borides, which also named as 'MAB' phases, are close structural analogs to the 'MAX' phases and believed to be more ductile and resistant to oxidation than binary borides. Although attentions have been drawn on their atomic arrangement and ground-state elastic properties, their thermal expansions and maintainability of mechanical properties at high temperatures have not been fully understood. Herein, with the combination of density functional theory (DFT) calculations and quasi-harmonic approximation (QHA), the mechanical and thermal properties of two MAB phases, MAlB (M = Mo, W), at ground-states and high temperatures were thoroughly investigated. The effects of transition metals on the structure, elastic anisotropy, thermal expansion, and temperature-dependent mechanical properties are discussed in detail. Possible improvement of high temperature mechanical properties of MoAlB by substitution of Mo by W is proposed.