Phase transition, microstructural evolution and mechanical properties of Ti-Nb-Fe alloys induced by Fe addition
Materials & Design
School of Engineering
Ti-11Nb-xFe (x = 0.5, 3.5, 6, 9 wt.%) alloys were designed and fabricated by cold crucible levitation melting to study the effects of Fe addition on their phase transition, microstructure and mechanical properties. Results show that phase and properties of the alloys depend on Fe additions. Ti-11Nb-0.5Fe alloy presents a typical α + β biphasic Widmanstätten microstructure. Increasing Fe content to 3.5 wt.% enhances β phase volume fraction. At 6 wt.% Fe, the resultant microstructure is changed to mainly β with minor amount of α ″ phase. Finally, when Fe content is 9 wt.%, the alloy exhibits a single β phase microstructure suggesting Fe addition is effective in suppressing α and α ″ formation, hence making β more stable. Compressive yield strength and hardness of the alloys are 796-1137 MPa and 278-357 HV5 respectively. It is noteworthy that upon increasing Fe content, the elastic modulus of the alloys decreases, while their plastic strain and elastic energy are enhanced due to retention of more β phase. The lowest elastic modulus (82 GPa) and highest plastic strain (38%) are observed in full β Ti-11Nb-9Fe alloy. Moreover, Ti-11Nb-9Fe presents higher elastic energy (7.08 MJ/m3) than that of some commercial Ti-based biomaterials. The results suggest that Ti-11Nb-9Fe is a promising candidate for biomedical applications.