The research on the properties of CoCrNiFeTiX high-entropy alloys for orthopedic implant potential application

In this study, the as-cast CoCrNiFeTi X (X = 0, 0.1, 0.2, 0.3 and 0.5 at.%) medium-entropy alloys (MEA) and high-entropy alloys (HEA) were investigated. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were processed to investigate the microstructure and the phase composition of the CoCrNiFeTi X MEAs and HEAs. The results showed that the Ti addition induced TiNi phase formation. The electrochemical behaviour of the alloys was analyzed. Compared with other orthopedic implants, the results showed that the alloys (−786.10 to −714.24 mV vs SCE and 1.029 to 0.513 μA/cm 2 ) met the requirements of corrosion resistance properties as orthopedic implants. The mechanical properties of the alloys were also evaluated. The result showed that CoCrNiFeTi 0.3 HEA (943.6 MPa in tensile strength and 112 GPa in modulus of elasticity and 0.43 in Poisson's ratio) exhibited better mechanical properties than the other MEAs and HEAs, meeting the requirement of mechanical properties as an orthopedic implant. The biocompatibility of the CoCrNiFeTi 0.1 , CoCrNiFeTi 0.3 and CoCrNiFeTi 0.5 was assessed. The results showed that the three samples exceeded 75 % viability and had excellent biocompatibility. Subcutaneous implantation confirmed good biological safety of samples. Overall, the HEAs met the requirement of biocompatibility and biological safety. In conclusion, CoCrNiFeTi 0.3 HEA had potential biomedical applications as orthopedic implants.