Effects of Element (Al, Mo, Sn and Fe) Doping on Phase Structure and Mechanical Properties of the Ti-Nb-Based Alloys

Abstract

In the paper, Ti-18Nb-5X (X = Mo and Sn) and Ti-33Nb-2X (X = Al, Sn, Fe and Mo) alloys were investigated to evaluate the effects of Al, Mo, Sn and Fe doping and different heat treatments on the properties and microstructures of the Ti-Nb-based alloys. The results show that Al decreased the volume of βM in the water-quenched Ti-33Nb-2Al alloy and promoted the formation of β phase in the furnace-cooled Ti-33Nb-2Al alloy. Fe-doping was proven to stabilize the β phase. Sn-doping plays a complicated role to promote the formation of α′′ phase in the water-quenched Ti-33Nb-2Sn alloys but increases the β phase in the furnace-cooled Ti-33Nb-2Sn alloys and Ti-18Nb-5Mo-5Sn. The alloys containing α′′ and βM phases show larger superelastic strains and lower Young’s moduli. In the water-quenched Ti-based alloys, the Young’s modulus decreases, and the superelastic strain is enhanced with the increasing volume of α′′.