Solution strengthening of ductile refractory HfMoxNbTaTiZr high-entropy alloys

•All the as-solidified HfMoxNbTaTiZr alloys have simple BCC structure.•The HfMoxNbTaTiZr alloys show significant solid-solution strengthening of Mo.•The yield strength increases from 1015 MPa to 1512 MPa with the increasing Mo addition from zero to 16.7 at%.•The studied alloys, except Mo-1 alloy, deform to 50% compression strain without any evidence of fracture.•The HfMoxNbTaTiZr alloys have linear correlation between yield strength and solute atom concentration.

The crystal structure, microstructure, and mechanical properties of HfMoxNbTaTiZr (x≤1) alloys were investigated by X-ray diffraction, scanning electron microscopy, and compression testing. All the as-solidified HfMoxNbTaTiZr alloys possess a simple body-centered cubic structure. Lattice parameters of the HfMoxNbTaTiZr alloys decrease with an increase in Mo concentration, but the corresponding densities show an opposite trend. The yield strength of the HfMoxNbTaTiZr alloys increases from 1015 MPa to 1512 MPa as x increases from 0 to 1. The solid solution strengthening is linearly proportional to a Mo concentration suggesting that the strengthening effect from each Mo atom is additive. Except for the HfMoNbTaTiZr alloy, HfMoxNbTaTiZr (x<1) alloys exhibit excellent room-temperature plasticity (>50%). The material with x=0.75 is a new ductile refractory high-entropy alloy with promising mechanical properties.