Sluggish dislocation mobility and high propensity for cross-slip at elevated temperatures in the MoNbTi Refractory Multi-Principal Element Alloy

Abstract

Numerous body-centered cubic (bcc) refractory multi-principal element alloys (RMPEAs) exhibit high-temperature strength that surpass the performance of Ni-based superalloys. The superior properties of RMPEAs have been shown to stem in part from the unique dislocation glide mechanisms in a compositionally disordered system. Here, we assess the temperature-dependent mobility of edge and screw dislocations in MoNbTi with a bcc, random solid solution microstructure. When both dislocation types are subjected to a Schmid stress state, we find that mobility is low compared to glide in pure Nb. Interestingly, the edge/screw mobility ratio is found to increase with temperature in MoNbTi due to sustained sluggish screw mobility. Under a non-Schmid stress state, it is revealed that cross-slip occurs more easily in MoNbTi than in Nb and at elevated temperatures.These findings support the notion that sluggish glide in RMPEAs contributes to high-temperature strength, while easy cross-slip contributes to high strain hardening.