First-principles investigation of the structural stability and mechanical properties of TM3Al2C(TM=Mo, Cr and W) carbides
Yong Pan
Abstract
Although Mo 3 Al 2 C MAX phase is a promising high temperature ceramics because of the high temperature strength and excellent oxidation resistance , the structural and mechanical properties of Mo 3 Al 2 C-type carbide is unknown. Here, we apply the first-principles method to study the structural stability , mechanical and thermodynamic properties of TM 3 Al 2 C MAX phase. Three refractory metals (TM=Mo, Cr and W) are considered. The calculated results show that the formation enthalpy follows the sequence of Mo 3 Al 2 C<Cr 3 Al 2 C<W 3 Al 2 C. Naturally, the structural stability of TM 3 Al 2 C carbides is determined by the formation of TM-Al bond, TM-C bond and TM-TM bond. Importantly, it is found that three TM 3 Al 2 C carbides are mechanical stability because the calculated elastic constants of these carbides meet the Born stability criteria. The calculated elastic constant C 11 of W 3 Al 2 C is 321.0 GPa, which is larger than the elastic constant C 11 for Mo 3 Al 2 C and Cr 3 Al 2 C. Importantly, the bulk modulus of W 3 Al 2 C is 249.9 GPa, which is larger than the elastic modulus of Mo 3 Al 2 C and Cr 3 Al 2 C. In addition, three TM 3 Al 2 C carbides show better ductility. Naturally, the bulk modulus of TM 3 Al 2 C is related to the TM-C bond and TM-TM bond in a a-b plane. However, the strength of shear modulus of TM 3 Al 2 C depends on the TM-C bond and TM-Al bond along the b- axis .