Ti-Zr-Nb-Ta-Sn Medium-Entropy Alloys with Excellent Properties as Potential Biomaterials

This study aimed to develop a new alloy for orthopedic implants by combining the concept of medium-entropy alloys (MEAs) with the performance requirements of medical alloys. The effects of Sn on microstructure, mechanical properties, electrochemical behavior, wettability, and friction & wear properties of Ti₄₀Zr₄₀Nb₅Ta_15-xSn_x (x = 3, 5, 7; at.%) MEAs were investigated. The results indicated that the Ti-Zr-Nb-Ta-Sn MEAs exhibited a single-phase BCC structure with lattice parameters of 0.3420 nm, 0.3439 nm, and 0.3447 nm, respectively. The alloys performed high yield strength (863 ± 7 ~ 1101 ± 8 MPa) with elongation up to ~ 10.6%, and hardness (291.6 ± 4.2 ~ 323.4 ± 3.2 HV). At the same time, these alloys showed the low Young's modulus (55.8 ± 1.3 ~ 68.0 ± 1.6 GPa). In the phosphate buffer saline (PBS) solution, the alloys displayed corrosion resistance comparable to that of the Ti6Al4V alloy, indicating it got excellent corrosion resistance. In the medium of deionized water and PBS solution, the alloys exhibited hydrophilicity. The wear resistance of the alloys increased substantially with increasing Sn content. In conclusion, Ti-Zr-Nb-Ta-Sn MEAs possessed high yield strength, relative low Young's modulus, and good corrosion and frictional wear resistance, making them promising materials for medical orthopedic implants.