Effect of Spark Plasma Sintering Heating Rate on the Mechanical and In Vitro Corrosion Behavior of Biomedical Ti-Zr-Nb-Ta-Ag High-Entropy Alloy in Simulated Body Fluid

This study examines the effect of the heating rate during spark plasma sintering (SPS) on the microstructure, microhardness, and electrochemical corrosion behavior of a Ti-Zr-Nb-Ta-Ag high-entropy alloy (HEA) in simulated body fluid (SBF). The HEA is produced via mechanical alloying and subsequent sintering, employing heating rates of 100, 200, and 300 °C min⁻¹. Microstructural analysis of the SPS-consolidated samples reveals the presence of BCC1, BCC2, and Zr-rich phases. An increase in the heating rate results in enhanced XRD peak intensities and crystallinity. However, this is accompanied by a decrease in both microhardness and relative density as the heating rate increases. At a heating rate of 100 °C min⁻¹, the alloy exhibits a microhardness of 9.945 GPa and a densification of 99.85%. The dominant phase in all the sintered samples is identified as BCC1. The in vitro corrosion resistance of the SPS samples increases at higher heating rates, indicating that a more stable and protective passive layer is developed in the SBF medium. These results underscore the critical role of optimizing the SPS heating rate to achieve a balance between the processing efficiency and mechanical and electrochemical performance of HEA.