High temperature dislocation glide in the MoNbTi refractory multiprincipal element alloy

Numerous body-centered cubic refractory multiprincipal element alloys (RMPEAs) exhibit high temperature strengths that surpass those of Ni-based superalloys. The superior properties of RMPEAs have been shown to stem in part from the unique dislocation glide mechanisms in compositionally disordered systems. Here, using a three-dimensional phase field dislocation dynamics approach combined with Langevin dynamics, we simulate the glide mechanisms of screw and edge dislocations at elevated temperature and low stress levels in the RMPEA MoNbTi with a body-centered cubic, random solid solution structure. For $600-1200$ K, edge-dislocation glide is smooth, temperature sensitive, and faster than screw dislocation glide. Screw dislocations exhibit three distinct glide mechanisms over the same temperature range. Ultimately, the formation of nonplanar kink pairs that ensues above 900 K reduces screw mobility with respect to temperature and leads to athermal mobility from 1100 to 1200 K.