An experimental and computational design low-modulus (HfNbTa)1-xTix multiprinciple elemental alloys with super formability for biomedical applications

Stress shielding at the implant-bone interface is the main causes of failure in orthopedic implant surgery, which is induced by the modulus mismatch between implants and bones. Reducing the Young's modulus of biomedical alloys is beneficial to alleviate the stress shielding effect. Recently, biomedical multiprinciple elemental (BioMPEAs) have aroused widespread concerns due to their low modulus, high strength, and superior biocompatibility. In this work, a series of (HfNbTa)1-xTix alloys are designed to investigate the effects of Ti content on the structural and mechanical properties of Bio-MPEAs. The obtained results reveal that the designed alloys have a single-phase body-centered cubic (BCC) structure, and exhibit ambient ductility with a tensile elongation >12% and cold-rolling thickness reduction >86%. Ti addition helps to reduce the Young's modulus of Bio-MPEAs. Their super formability stems from the movability of <1 1 1>/2-type dislocations. Solid solution strengthening is the major strengthening mechanism of the alloys. Local lattice distortion plays a key role in solid solution strengthening, which is induced by atomic size mismatch and electronegativity difference of multiple elements. This work not only highlights the positive role of Ti addition for designing low-modulus Bio-MEAs, but also clarifies the physical mechanisms of solid solution strengthening and lattice distortion.