Thermal Super-Jogs Control High-Temperature Strength in Nb-Mo-Ta-W Alloys

Refractory multi-element alloys (RMEA) with body-centered cubic (bcc) structure have been the object of much research over last decade due to their high potential as candidate materials for high-temperature applications. Most these display a remarkable strength at temperatures, which cannot be explained by standard model bcc plasticity dominated thermally-activated screw dislocation motion. Recent on Nb-Mo-Ta-W points heightened role edge dislocations deformation, is generally attributed atomic-level chemical fluctuations in material and interactions cores during slip. However, while this accounts strengthening effect complexity alloy, it not sufficient explain its across entire thermal range. Here we propose new mechanism that captures existing theories about enhanced lattice component emanates directly from RMEA. This compositional results unique vacancy formation energy distributions tails extend into negative energies, leading spontaneous, i.e., athermal, cores. These vacancies relax atomic-sized super-jogs line, acting extra pinning increase activation stress dislocation. At same time, can displace diffusively along glide direction, relieving motion some stress, thus countering hardening jog-pinning. The interplay between two processes function temperature confers an intermediate-to-high agreement experimental measurements number different