Development of TiNbTaZrMo bio-high entropy alloy (BioHEA) super-solid solution by selective laser melting, and its improved mechanical property and biocompatibility

BioHEAs, specifically designed high entropy alloy (HEA) systems for biomedical applications, represent a new era for biometals. However, recent challenges are (1) the poor shape customizability, and (2) the inevitable severe segregation due to the intrinsic fact that HEA is an ultra-multicomponent alloy system. To achieve shape customization and suppression of elemental segregation simultaneously, we used an extremely high cooling rate (~10⁷ K/s) of the selective laser melting (SLM) process. We, for the first time, developed pre-alloyed Ti_1.4Nb_0.6Ta_0.6Zr_1.4Mo_0.6 BioHEA powders and SLM-built parts with low porosity, customizable shape, excellent yield stress, and good biocompatibility. The SLM-built specimens showed drastically suppressed elemental segregation compared to the cast counterpart, representing realization of a super-solid solution. As a result, the 0.2% proof stress reached 1690 ± 78 MPa, which is significantly higher than that of cast Ti_1.4Nb_0.6Ta_0.6Zr_1.4Mo_0.6 (1140 MPa). The SLM-built Ti_1.4Nb_0.6Ta_0.6Zr_1.4Mo_0.6 BioHEA is promising as a next-generation metallic material for biomedical applications.