Recycling Ti1.0Nb0.3Ta0.07Zr0.05 Conventional Alloys: Production of Non-equimolar TiZrCrNb0.3Ta0.07 Medium Entropy Alloys with the Addition of Cr for Improved In Vitro Corrosion Resistance

A non-equimolar TiZrCrNb0.3Ta0.07 medium entropy alloy (MEA) was successfully designed as theoretical and produced by arc-melting method from Ti1.0Nb0.3Ta0.07Zr0.05 (TNTZ) scraps for possible usage in biomedical applications in this study. The main aim of this study is to find an alternative way to recycle with a reduced carbon footprint the available TNTZ conventional alloy and convert it to a value-added product during this recycling such as medium entropy alloys (MEAs) via using less energy. To examine the microstructural changes induced by the annealing process, scanning electron microscopy was employed. The chemical composition of the HEAs was assessed using energy-dispersive spectroscopy and x-ray photoelectron spectroscopy. Additionally, x-ray diffraction analysis was used to determine the crystallographic structure and phase composition of HEAs. Furthermore, in order to evaluate the electrochemical corrosion performance of the alloys, comprehensive in vitro corrosion tests were conducted in a simulated body fluid solution, specifically Hanks's Balanced Salt Solution. Some elemental segregation has been observed after the annealing process. A big migration of Zr and Cr elements was observed in the samples from the interdendritic region to the dendritic area during the annealing process. This segregation resulted in approximately 1.4 times increase in the hardness of the MEA. The electrochemical corrosion results showed that the in vitro resistance of the MEAs was higher than that of its conventional scraps.