Microstructure evolution, deformation mechanism, and mechanical properties of biomedical TiZrNb medium entropy alloy processed using equal channel angular pressing

Abstract

Equal channel angular pressing (ECAP) was applied to a biomedical TiZrNb medium entropy alloy (MEA) with an equal atomic ratio at 480 °C with 1, 2, 4, and 6 deformation passes in route C to enhance the mechanical properties and exploit the plastic deformation mechanism of the MEA. As the applied strain increased, dendritic grains first tended to merge and form equiaxed grains, which eventually elongated and formed coarse grains. Simultaneously, many straight dislocations and dislocation loops occurred and coalesced into a line during the early stages. Then, they rearranged to construct highly dense dislocation walls (HDDWs) and evolved into shear bands, maintaining the continuity of the deformation. After a 6-pass deformation, the TiZrNb MEA exhibited a yield strength of 1170 ± 21 MPa, higher than that of the as-cast sample of 830 ± 21 MPa, and a maximum hardness of 389 ± 11 HV0.2, which enhanced its wear resistance.