Edge dislocation-induced high-temperature strengthening in the Ti37V15Nb22Hf23W3 refractory high-entropy alloys

Abstract

The Ti37V15Nb22Hf23W3 is a multi-principal refractory alloy with exceptional strength and ductility at room temperature. For potential high-temperature applications, it is of great significance to investigate the deformation mechanism at different temperatures through tensile tests. The yield strength (YS) has a substantial temperature dependency from 298 K to 473 K, nevertheless is insensitive between 473 K and 1073 K, with a large decline at 1223 K. At 1,073 K, the yield strength of 550 MPa is still maintained, which has nearly exceeded most commercial alloys. The transmission electron microscopy (TEM) experiments revealed that the plastic deformation was controlled by dislocation slip, and the degree of deformation was strongly related to the dislocation density. The proportion of edge dislocations gradually increases as the temperature rises. When the temperature reaches 1073 K, the deformed dislocations are almost all edge dislocations. Edge dislocations control the strength of the alloy at high temperatures. The yield strength of the alloy is predicted using the edge dislocation strengthening model, which is in good agreement with the experimental values. The excellent high-temperature mechanical properties of the Ti37V15Nb22Hf23W3 RHEAs indicate that it is potential to be used in future.