Abstract: Ti₄₅Zr₂₀Nb₁₅V_(10-x)Al₁₀Mo_x (x=0, 0.5, 1.0) refractory high entropy alloy was prepared by adding trace amounts of Mo element to the Ti₄₅Zr₂₀Nb₁₅V₁₀Al₁₀ refractory high entropy alloy matrix, which strain hardening ability and plasticity were improved by deformation heat treatment. Microstructure and mechanical properties of the as-cast specimen and cold-rolled (deformation of 80%) and annealed (600 ℃×5 h and 800 ℃ for 1 h) specimen were investigated using X-ray diffractometer, field emission scanning electron microscope, and universal mechanical testing machine. The test results show that the as-cast alloy has a single-phase BCC structure, and the addition of Mo element increases the yield strength and maintains a fracture elongation of about 10%. After cold rolling and annealing, the microstructure of the alloy becomes BCC+Al₃Zr₄ dual phase with a large amount of approximately spherical nanoscale Al₃Zr₄ particles precipitated at and near grain boundaries, causing the alloy to transition from strain softening to strain hardening, and the yield strength of the alloy is maintained at 1100 MPa, while the fracture elongation is significantly improved. When the Mo content is 0.5%, the fracture elongation of the alloy after cold rolling annealing increases from 9.9% in as-cast state to 16.9%, exhibiting excellent strength plasticity matching and a density of only 5.638 g/cm³.

Key words: refractory high entropy alloy, deformation heat treatment, strain hardening, microstructure, tensile properties