Abstract: Achieving a balance between mechanical compatibility and biocompatibility in biomedical load-bearing metallic materials has long been a significant challenge. In this study, the d-electron alloy design theory in combination with the first-principles calculation and the calculation of phase diagrams was employed to design novel high-entropy alloys composed entirely of non-toxic elements for biomedical applications. By accurately tuning the parameters $ \overline{B o}$ and $ \overline{M d}$ to control the phase stability, as-cast Ti-Zr-Nb-Hf-Ta biomedical high-entropy alloys with remarkably low Young’s modulus, high yield strength, and large fracture elongation were developed without the need for intricate post-processing steps. The alloys are composed of single metastable β phase with an inhomogeneous distribution of elements at the nanoscale in it. The feature of metastable β phase and the binding energy approaching 0 eV/atom among the component atoms determine the low Young’s modulus, while the high strength is mainly related with the solid solution strengthening and the presence of HfTa-rich clusters that can pin the movement of dislocations effectively, resulting in the excellent strength-ductility synergy. This work provides new insights into the development of biomedical load-bearing implant materials through multicomponent design.

Key words: High-entropy alloy, Biomedical material, Alloy design, Microstructure, Mechanical property