An Insight into the Unusual Grain Orientation Evolution and Mechanical Property Anisotropy in Hot-Rolled Wmotav Refractory High Entropy Alloy with Interfacial Segregation

Abstract

The microstructural modification of refractory high entropy alloys (RHEAs) during rolling is a recognized technology for improving their mechanical properties, but limited researches are available for the internal coupling of macroscopic deformation and grain orientation evolution. In the present work, a single BCC WMoTaV RHEAs was hot-rolled to different reduction in thickness. The evolution process of their microstructure, texture and mechanical properties was fully tracked. A distinct BCC W-enriched nanolayer exists in hot-rolled WMoTaV RHEAs. This nanolayer impedes grain orientation rotation as well as deformation, most grains gathered to some orientations. Thus, the angle differences between rolled grains c-axis and 〈001〉 basal texture is mainly concentrated in 0-70°, no texture component with 70°-90° appears. This is distinct from the ubiquitous rolling grain orientation. Moreover, the dominant strong basal 〈001〉//ND texture and 〈111〉//ND textures exist in rolling grains with 0-20° and 45°-70°, respectively. As improving rolling reduction, the strong basal texture alters to inhibit deformation, thereby activating non-basal dislocation slip to accommodates large plastic deformation, then contribute to yield strength-plasticity synergy. Meanwhile, the geometrically necessary dislocations (GND) density increases and distributes uniformly to coordinate microscopic deformation and maintain strain continuity. Under the joint contribution of grain boundary, dislocation and texture, the rolling sample with 60% reduction achieves an ultrahigh yield strength (1524 MPa) and plasticity (8.1%) trade-off along the rolling direction compared to typical RHEA alloys. These findings hold promise for further optimizing alloy properties.

Keywords: grain orientation, Interfacial segregation, Mechanical property, Hot-rolling, Refractory high-entropy alloys