Local slip resistances in equal-molar MoNbTi multi-principal element alloy

https://doi.org/10.1016/j.actamat.2020.10.042

Abstract

In this work, we calculate the local slip resistances (LSRs) in equal-molar MoNbTi multi-principal element alloy via molecular static simulations. We consider dislocations of either screw or edge character gliding on four types of slip planes, {110}, {112}, {123}, and {134}, in either forward or backward sense of the <111> slip direction. As references, we also compute the Peierls stresses of the same dislocations in two natural reference metals, Mo and Nb, and a synthetic one, the mean-field, A-atom potential-based MoNbTi. Further, we compare the LSRs with the corresponding ideal shear strengths that do not account for the lattice distortions induced by dislocation cores. We show that for neither dislocation character is the LSR on the {110} plane the lowest in MoNbTi, in contrast to Mo and Nb. For edge dislocations, slip on the {134} plane is the easiest, but for the screw dislocations, it is the hardest. For screw dislocations, the {112} glide plane is the most favored, while for edge dislocations, it is the least favored. We also find that the screw-to-edge ratio in the slip resistance is reduced by one order of magnitude in MoNbTi compared to that of any pure reference metal for the same type of slip plane. These results suggest that, in contrast to pure body-centered cubic (BCC) metals, BCC MPEAs could deform by a multiplicity of slip modes due to the lower screw-to-edge ratios and the lower LSRs for edge dislocations on the three higher order planes.