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 degrees C. A dominant alpha '' martensite and minor beta 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)(beta) [(13) over bar2](beta) and weak gamma-fiber deformation textures were observed in the 5Sn alloy specimen and the {001}(beta) < 110>(beta) recrystallization texture was developed in the 3Sn alloy specimen. Also, increasing Sn content was found to effectively stabilize the beta phase. 1 at.%-Sn addition decreased the alpha '' -> beta reverse transformation start temperature (A(s)) and finish temperature (A(f)) by 75 degrees C and 106 degrees C, respectively. The superelasticity was distinctly observed in the 900 degrees C annealed 5Sn alloy specimen at room temperature because its A(f) was below the room temperature.