Microstructure, Mechanical Properties and Incipient Plasticity of (Ti42.5zr42.5nb10ta5)100-Xmox Refractory High Entropy Alloys

Abstract

A series of (Ti42.5Zr42.5Nb10Ta5)100-xMox (x=0, 3, 5 and 7 at.%) refractory high entropy alloys (RHEAs) were prepared, and the influence of Mo content on  microstructure and mechanical properties of the RHEAs were systematically studied. All the RHEAs consist of single body-centered cubic (BCC) phase. As the Mo content increases from 0 at.% to 7 at.%, the yield strength of RHEAs increases from 670 MPa to 975 MPa. The high strength of the BCC RHEAs mainly depends on solid-solution strengthening caused by the Mo addition. The RHEAs with low Mo content (0~5 at.%) can possess high tensile plasticity of ~20 %, while it reflects brittle after the 7 at.% Mo addition. The high tensile plasticity of the RHEAs was attributed to the combined effects of dislocation aggregation and lattice rotation promote. Moreover, the incipient plasticity of the RHEAs was analyzed by nanoindentation. It is shown that the maximum shear stress (τmax) of the RHEAs from 1.80~2.34 GPa to 2.67~4.83 GPa. The activation volumes (v∗) of the RHEAs from 0.7Ω to 1.1 Ω. The nanomechanical properties of the RHEAs are related to the Mo content.

Keywords: Refractory high entropy alloy, microstructure, Mechanical properties, Nanoindentation