Effects of La and Y on the microstructure and mechanical properties of NbMoTiVSi0.3 refractory high entropy alloys

Effects of La and Y on the phase composition, microstructure and mechanical properties of NbMoTiVSi0.3 RHEAs were systematically studied. The results show that all the alloys consist of BCC and M5Si3 phases, and most of La and Y distribute at the grain boundary. With the addition of La and Y, the morphology of M5Si3 phase changes from large net-like structure to spherical and blocky structure, meanwhile the H, E and H3/E2 of BCC and M5Si3 phases are improved. The yield strength of RHEAs increases from 1641.10 MPa to 1920.93 MPa for 0.5 at.% La and 1991.59 MPa for 0.5 at.% Y, respectively. Meanwhile, the compression plasticity of RHEAs increases from 12.68 % to 16.82 % for 0.5 at.% La and 16.58 % for 0.5 at.% Y, respectively. The specific strength of the three RHEAs are 236.81, 277.59, 287.80 MPa·cm3/g, respectively. The addition of La and Y is beneficial to the mechanical properties of NbMoTiVSi0.3 RHEA, especially for the Y addition. •The addition of La and Y facilitates the spheroidization and refinement of M5Si3 in the NbMoTiVSi0.3 RHEAs.•A large amount of La and Y distribute at the phase interface of BCC phase and M5Si3 phase.•With the addition of La, the yield strength increases from 1641.101641.10 MPa to 1920.93 MPa, and the compressive strain increases from 12.68% to 16.82 %.•With the addition of Y, the yield strength increases to 1991.59 MPa and the compressive strain increases 16.58 %.