Plastic deformation of solid-solution strengthened Hf-Nb-Ta-Ti-Zr body-centered cubic medium/high-entropy alloys

Plastic deformation and rate-controlling mechanism during tensile deformation of various body-centered cubic (BCC) medium/high-entropy alloys (MEAs/HEAs) were investigated at 300 K. Microstructural observations revealed long, straight screw dislocations, occasionally consisting of jogs. The deformed substructures were consistent with the evaluated activation volume (V*) indicating screw dislocation motion overcoming the Peierls-Nabarro stress barrier as the rate-controlling mechanism. The V* values were found inversely proportional to the yield strength. The monotonous behavior of the V* as a function of yield strength indicated the dislocation motion of BCC-MEAs/HEAs must involve overcoming the energy barrier involving multiple/group of substitutional solute atoms, simultaneously. Furthermore, for the first time, stress equivalence was observed in the BCC-MEAs/HEAs. The findings described thermally-activated dislocation glide mechanisms of the solid-solution strengthened BCC-MEAs/HEAs depended on the stress rather than the chemical complexity of the alloys.