Mechanical Properties and Biocompatibility of Ti58−x–Zr40–Nbx–Al2 Medium Entropy Alloy for Osteogenic Applications

Abstract Low elastic modulus and high strength properties are essential for osseous implants to avoid stress shielding without compromising strength requirements. For this reason, Ti–Zr-based medium entropy alloys (MEAs) are considered potential candidates in the medical and dental fields thanks to their low elastic modulus, high yield strength, and high biocompatible elements. In the current study, the mechanical properties and biocompatibility of arc-melted Ti 58− x –Zr 40 –Nb x –Al 2 MEAs were assessed for osteogenic applications, where x = 9 and 11 at. pct. The formation of the solid solution was verified using X-ray diffraction (XRD) in both Ti 49 –Zr 40 –Nb 9 –Al 2 and Ti 47 –Zr 40 –Nb 11 –Al 2 MEAs. The elastic modulus was physically measured using an ultrasonic echo system. Adding more Nb, which is a beta phase stabilizing element, decreased the total valence electron and hence reduced the Young’s modulus from 66 ± 1.5 GPa for 9Nb to 62 ± 2.3 GPa for 11Nb alloy. The hardness increased from 245 to 270 HV with the increase in Nb content from 9 to 11 at. pct, indicating improvement of strength by providing more solutes for solid solution strengthening. To assess the bioactivity of the prepared alloy samples, the alloys were incubated in simulated body fluid (SBF) for 4 weeks, after which they were examined using an Atomic Force Microscope (AFM) both before and after incubation. AFM results analysis showed a uniform vs nonuniform calcium phosphate layer precipitation for 9Nb and 11Nb alloys, respectively. Graphical Abstract