Effect of Nb Content on Superelastic Properties of Biomedical Ti–Zr-Based Shape Memory Alloys

Ti–18Zr– x Nb–2Sn ( x = 10, 11, 11.5, 12, 12.5) (at.%) shape memory alloys were fabricated by arc melting then phase constitutions and superelastic properties were investigated by X-ray diffraction (XRD) and tensile test at various temperatures between 178 K and 413 K. Excellent superelasticity was observed in 12.5Nb alloy at temperatures between 258 K and 298 K. Both superelasticity and shape memory effect were observed in 12Nb alloy at temperatures between 233 K and 383 K. Only shape memory effect was observed in 11Nb and 11.5Nb alloys at temperatures between 298 K and 383 K. 12.5Nb and 12Nb alloys consisted of the main β phase and athermal ω . The amount of β phase decreased with increasing Nb content. 10Nb alloy consisted of main α″ martensite and a small amount of β phase. The M s temperature measured from the Clausius–Clapeyron relationship decreased greatly with increasing Nb content (100 K/at.% Nb) in these Ti–Zr–Nb–Sn alloys.