Effect of Sn content on microstructure, texture evolution, transformation behavior and superelastic properties of Ti–20Zr–9Nb‒(2–5)Sn (at.%) shape memory alloys

Abstract

In the present study, the effects of Sn content on microstructure, texture evolution, transformation behavior and superelastic properties of Ti–20Zr–9Nb‒(2–5)Sn (at.%) shape memory alloys were systematically investigated. After severe cold-rolling at room temperature, the sheet was annealed at 900 °C. A dominant α″ martensite and minor β phase were formed in the 2Sn alloy specimen. (Ti,Zr)5(Nb,Sn)3 s phase started to be detected in the 3Sn alloy specimen, and its area fraction increased from 0.02% to 1.75% with increasing Sn content from 3 at.% and 5 at.%. Increasing Sn content prevented recrystallization, affecting the texture evolution. A dominant (112)β[1‾3‾2]β and weak γ-fiber deformation textures were observed in the 5Sn alloy specimen and the 001β<110>β recrystallization texture was developed in the 3Sn alloy specimen. Also, increasing Sn content was found to effectively stabilize the β phase. 1 at.%‒Sn addition decreased the α″ → β reverse transformation start temperature (As) and finish temperature (Af) by 75 °C and 106 °C, respectively. The superelasticity was distinctly observed in the 900 °C annealed 5Sn alloy specimen at room temperature because its Af was below the room temperature.