Influence of composition ratios on the microstructure and properties of low-modulus biomedical TiZrNbTaSn medium-entropy alloys

Biomaterials with low elastic modulus have been crucial for the development of bone implants. The microstructure, mechanical properties, corrosion behavior, and tribological performance of newly developed Ti 1.5 Zr 0.5 NbTa 0.5 Sn 0.2 , Ti 1.8 Zr 1.5 NbTa 0.5 Sn 0.2 , Ti 1.5 Zr 1.8 NbTa 0.5 Sn 0.2 and Ti 1.75 Zr 0.5 Nb 0.5 Ta 0.5 Sn 1.75 alloys were comparatively investigated for potential orthopedic applications. Four non-equiatomic TiZrNbTaSn medium-entropy alloys were fabricated via vacuum arc melting. Their phase structure, surface morphology, wear mechanisms, nanoindentation reduced modulus, and corrosion resistance were characterized using X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, tribological testing, nanoindentation, and potentiodynamic polarization techniques. Results showed that the Ti 1.5 Zr 1.8 NbTa 0.5 Sn 0.2 alloy exhibited the most favorable overall performance, with a nanoindentation reduced modulus of 61 GPa, hardness of 273 HV, and a compressive yield strength of 783 MPa, wear rate of 4.00 × 10 −6 mm 3 /(N·m), and corrosion current density of 0.03 μA/cm 2 . The newly developed TiZrNbTaSn medium-entropy alloys primarily exhibited a BCC structure. Ti 1.5 Zr 1.8 NbTa 0.5 Sn 0.2 exhibited a homogeneous single-BCC2 structure and relatively uniform elemental distribution, together with a favorable overall balance of mechanical, tribological, and electrochemical properties. Ti 1.75 Zr 0.5 Nb 0.5 Ta 0.5 Sn 1.75 exhibited a heterogeneous multiphase structure containing BCC2, HCP, and an oxide-related contribution, together with the highest hardness and premature fragmentation during compression. These newly developed non-equiatomic TiZrNbTaSn medium-entropy alloys exhibit a favorable combination of nanoindentation reduced modulus, mechanical performance, wear resistance, and electrochemical behavior, highlighting their potential for biomedical alloy development.