Synthesis of biocompatible high-entropy alloy TiNbZrTaHf by high-pressure torsion

High-entropy alloys (HEAs), a novel type of materials with high configurational entropy, have aroused a huge interest due to a promising range of functional properties including biocompatibility. In this study, the high-pressure torsion (HPT) method was implemented as a mechanical alloying route to synthesize biocompatible nanostructured HEAs with the bcc structure. An equiatomic quinary TiNbZrTaHf HEA was successfully synthesized via the HPT method and its characteristics were compared with the binary TiNb, ternary TiNbZr and quaternary TiNbZrTa alloys to have an insight into the effect of configurational entropy on microstructure and mechanical properties of these biomaterials. The grain size decreased, the strain-rate sensitivity reduced, and the hardness increased with increasing the number of principal elements from 2 to 3, but these variations became less significant with further increase in the configurational entropy. Small nanograins, solid solution hardening, dislocation activity together with high entropy effect in the HEA led to a high hardness of 564 Hv and a moderate elastic modulus of 79 GPa which are promising mechanical properties for biomedical applications.