Fabrication of porous TiZrNbTa high-entropy alloys/Ti composite with high strength and low Young's modulus using a novel MgO space holder

Stress shielding is caused by the mismatch of stiffness between bone and implant materials, which may give rise to bone resorption and loosening, thereby causing implantation failure. There is a huge gap between Young's modulus of human bone and low Young's modulus β Ti alloys. A porous structure design can achieve the target of low Young's modulus, and thus achieve the matching between human bone and implant materials. However, a suitable space holder (SH) that can be applied at high temperatures and sintering pressure has not been reported. In this study, the TiZrNbTa/Ti titanium matrix composite (TMC) with high strength and large ductility was used as scaffold materials and combined the SH technique with the spark plasma sintering (SPS) technique to obtain a porous structure. A novel space holder, i.e., MgO particles was adopted, which can withstand high-temperature sintering accompanied by a sintering pressure. The porous TiZrNbTa/Ti with 40 vol.% MgO added exhibits a maximum strength of 345.9 ± 10.4 MPa and Young's modulus of 24.72 ± 0.20 GPa, respectively. It possesses higher strength compared with human bone and matches Young's modulus of human bone, which exhibits great potential for clinical application.