Development of a Ti49Zr20Hf15Al10Nb6 high entropy shape memory alloy for biomedical applications

Abstract

Titanium (Ti)-rich high entropy shape memory alloys (HESMAs) exhibit excellent mechanical properties and the biocompatibility of Ti alloys. Researches on the biomedical applications of the HESMAs are urgently needed to identify metallic biomaterials superior to the traditional Ni–Ti and Ti–6Al–4V (Ti64) alloys. In this study, a Ti-rich HESMA, designated as Ti₄₉Zr₂₀Hf₁₅Al₁₀Nb₆ (in atomic percent, at. %), was synthesized using an arc melting and suction casting method. The investigation focused on its mechanical properties, superelasticity, wear resistance, corrosion resistance, and biocompatibility. The Ti-rich HESMA demonstrated superior attributes in terms of strength, elastic modulus, wear and corrosion resistance, and biocompatibility when compared to Ni–Ti and Ti64 alloys. Despite its elemental complexity, the as-cast Ti-rich HESMA achieved a homogeneous composition and maintained a sole β phase consisting of equiaxed grains with an average size of 52 μm, leading to a low elastic modulus of 83.9 GPa. Notably, the Ti-rich HESMA exhibits superelasticity at room temperature, with a maximum recoverable strain of approximately 3.8 %. Moreover, it demonstrates superior wear resistance compared to Ni–Ti and Ti64. Additionally, the Ti-rich HESMA shows high corrosion resistance in Hanks’ solution and favorable cytocompatibility relative to Ni–Ti and Ti64. Overall, the Ti-rich HESMA represents a promising avenue for the development of innovative metallic biomaterials.