Microstructure and mechanical properties of TiZrVMnCu high entropy alloy by addition of Er element

•The good mechanical properties are mainly contributed to the effective combination of the hard TiZrVMn and soft CuZr phases.•The addition of Er obviously refined the grain size.•Er decreased the ZrO2 content and increased the relative densities and mechanical properties.•Excess Er2O3 particles deteriorated the mechanical properties. To improve the ductility and toughness of refractory high entropy alloys (HEAs), TiZrVMnCu-xEr HEAs were designed and fabricated via spark plasma sintering. With the addition of Er, the relative density, microhardness, and compressive strength of the HEAs increased. TiZrVMnCu-0.5 %Er HEA has the highest compressive strength (1520.5 MPa) and good deformation ability (strain 14.7 %). The good mechanical properties are mainly contributed to the effective combination of the hard TiZrVMn and soft CuZr phases. Appropriate Er content can: (i) reduce the content of ZrO2 and improve the relative densities; (ii) diffuse into matrix to achieve solid solution strengthening; (iii) refine the grains. Excess Er2O3 particles deteriorated the mechanical properties.