Design and development of MoNbTaTiZr Porous High Entropy Alloys for Biomedical Applications

Abstract

Titanium and Ti based alloys drawn significant attention than conventional counterparts (CoCr Mo, 316L SS) as orthopedic implant application due to suitable mechanical properties and sufficient chemical stability in physiological body environment. In the present study, b-type high entropy alloy MoNbTaTiZr with varying concentration of filler element was designed by thermo calc software and developed by arc melting route. 3D inter-connected porosity with porosity range (4.1,8.7,14 & 18%) was introduced with removal of filler element by novel chemical dealloying method. XRD and SEM results confirmed the formation of dual BCC microstructure. The elastic modulus and mechanical strength of implant are successfully optimized by synergetic effect of high entropy alloys and porosity. The elastic modulus tailored between (42- 3.5) GPa and yield strength between (803- 108.5) MPa respectively. The microhardness values are higher than bone. Interconnected open cell 3d porous structure enhance surface roughness, surface area and hydrophilicity thus enhance bioactivity. Metallic implants surface was alkali treated to enhance surface energy then coated with hydroxyapatite by biomimetic method to enhance bioactivity. Corrosion studies of high entropy foams were carried out in simulated body fluid at body physiological conditions. The developed foams show higher corrosion resistance and electrochemical stability, required for biomedical applications. Overall developed high entropy foams consist of biocompatible elements, shows superior mechanical properties then conventional materials used and are best suited material for orthopedic implants.