Local slip resistances and critical resolved shear stresses for edge dislocation glide on high-order planes in two refractory multiprincipal element alloys

Refractory multiprincipal element alloys (RMPEAs) are emerging as promising candidates for extreme-temperature applications; yet, their dislocation-mediated plasticity remains insufficiently understood. Using atomistic simulations, we systematically quantify the local slip resistance (LSR), initial critical resolved shear stress (ICRSS), and CRSS for the glide of an edge dislocation in two RMPEAs (MoNbTi and NbTiZr) and one refractory pure metal (Nb) across {123} and {134} slip planes for both hard- and easy-glide directions. MoNbTi exhibits the highest LSR on the {123} plane for the hard-glide direction (795.84 MPa), more than double that of NbTiZr (344.02 MPa). Both ICRSS and CRSS values show strong line-length dependence. For example, CRSS reaches 897.2 MPa in MoNbTi and 384.2 MPa in NbTiZr at 1 nm—on par with LSR, before converging to plateau stresses of about 370 MPa and about 239 MPa, respectively, beyond 30 nm. The close correspondence between LSR and short-segment ICRSS and CRSS suggests that LSR can be used to indicate the intrinsic slip resistance to a certain degree. Directional anisotropy is more pronounced on the {123} plane than on the {134} plane and is more pronounced in MoNbTi than in NbTiZr. We also find that sometimes in the same material and on the same slip plane, the easy-glide critical stress may surpass its hard-glide counterpart, suggesting a deviation from the theoretical prediction in complex alloys. Taken together, our results advance the understanding of the relationship between chemical complexity and plasticity, pointing toward alloy design strategies for next-generation high-temperature structural materials.