Phase transformation and mechanical properties of Ti-(10–30)Zr–3Mo–1Sn alloys

Studies on three Ti–xZr–3Mo–1Sn (x=10–30 at.%) alloys found that the influences of Zr on phase transformation and mechanical properties are closely tied to its effect on β-phase stability. It decreases the β-transus by ~8.8 °C/at.%, suppresses the formation of α-phase or martensite during cooling and enhances the room temperature super-elasticity. The influence of Zr on lattice transformation strain is weak with the calculated maximum transformation strains of ~8% in all three alloys regardless of their large differences in Zr content. The largest recoverable strain of ~3.8% was obtained in alloy 30Zr after heat treatment at 600 °C. Heat treating at 600 °C produces a α+β dual phase structure with unique texture patterns in alloys 10Zr and 20Zr. Although texture patterns of α and β phases can be understood based on their crystal orientation relationship, mechanisms that caused these textures remain unknown. Aging at 200 °C for a short time increases the super-elastic strain without sacrificing material ductility and total recoverable strain.