Effect of SPS sintering temperature on the microstructure and mechanical properties of the WNbTaVTi refractory high entropy alloy

Abstract

In order to improve the plasticity of WNbTaV refractory high entropy alloy (RHEA) at room temperature, the WNbTaVTi RHEA was successfully synthesized by spark plasma sintering (SPS) technology. The effect of sintering temperature on the microstructure and mechanical properties of the WNbTaVTi RHEA was investigated. The WNbTaVTi powders after 24 h of ball milling predominantly consisted of individual elemental components, with no detectable amorphous phases or alloy formation. RHEAs sintered at 1500 and 1600 °C were primarily composed of a BCC phase and a TiO phase, whereas those sintered at 1400 °C included a BCC phase, TiO phase, and a small amount of W-rich phase. The presence of the W-rich phase was due to the insufficient diffusion of high-melting-point W atoms during rapid heating. As the sintering temperature increased, the grain size and relative density of the WNbTaVTi RHEA rose, while the dislocation density decreased. The compressive plasticity of RHEA decreased with the increase of sintering temperature, while the Vickers hardness, nanohardness, and compressive strength first increased and then decreased, which was related to the combined effects of solid-solution strengthening enhancement, reduction in porosity, grain growth, and increased dislocation mobility. At the sintering temperature of 1500 °C, the RHEA demonstrated optimal comprehensive performance, with a yield strength of 2310.1 MPa, a compressive strength of 2893.3 MPa, and a fracture strain of 12.6 %. The properties of the present WNbTaVTi RHEA surpassed those of most RHEAs documented in literature.