Effect of ternary alloying elements on microstructure and superelastictity of Ti–Nb alloys

The effect of ternary alloying elements (X=Ta, Fe, Zr, Mo, Sn and Si) on the microstructure, the mechanical properties and the superelasticity of Ti–-22Nb–X alloys were investigated. The 1% addition of a ternary alloying element (X=Ta, Fe, Zr, Mo, Sn and Si) has a slight influence on the microstructure of the Ti–22Nb alloy. All the alloys after solution-treatment at 1073 K for 1.8 ks contain β and α″ phases. The elements of Sn, Si, Fe and Ta with a high number of valence electrons or a small atomic size have a strong solid–solution strengthening effect to the β phases in the alloys and the alloys with high Md¯ and low Bo¯ exhibit low elastic moduli. All the alloying elements improve the superelasticity of Ti–22Nb–X alloys. The elements, Fe, Mo, Sn and Si, which are with a high number of valence electrons and a small atomic size, strongly increase σSIM of the Ti–22Nb alloy.