New Ti-Ta-Zr-Nb alloys with ultrahigh strength for potential orthopedic implant applications

In this study, a new series of Ti-Ta-Zr-Nb alloys (Ti-38.3Ta-22Zr-8.1Nb, Ti-38.9Ta-25Zr-5Nb, Ti-39.5Ta-28Zr2.5Nb, designated TTZN-1, TTZN-2, TTZN-3, respectively) with high elastic strain and high mechanical strength have been developed as alternatives to conventional orthopedic implant materials. The TTZN alloys have been designed using the electronic parameters of the alloying elements, combined with the approaches of the electron to-atom ratio (e/a) and molybdenum equivalence (Mo-eq). X-ray diffraction analysis has revealed that all the TTZN alloys are comprised of a single 13 phase, however, transmission electron microscopy observations revealed that omega and beta phases co-existed in the microstructure. The compression strains of the TTZN alloys range from 22% to 36% and the compression strength from 1787 to 1807 MPa. The tensile Young's modulus, elastic strain and yield strength are 73.12 +/- 4.43, 74.98 +/- 2.19 and 76.62 +/- 2.38 (GPa); 1.57 +/- 0.27, 1.25 +/- 0.27 and 1.29 +/- 0.16 (%); and 1107.42 +/- 144.68, 932.11 +/- 195.22 and 953.58 +/- 120.76 MPa for TTZN-1, TTZN-2 and TTZN-3, respectively. Further, all the TTZN alloys exhibit excellent cytocompatibility as their cell adhesion density is higher than that of CP-Ti. This study demonstrates that these TTZN alloys can be anticipated to be promising candidate for orthopedic implant materials due to their high mechanical strength and high elastic strain.