Effect of Carbon Addition of Shape Memory Properties of TiNb Alloys

In order to increase critical stress for slip in Ti-Nb base shape memory alloys, strengthening by carbon additions (0.2 and 0.5mass%C) to Ti-27mol%Nb was investigated It was found that all the alloys were beta (bcc) phase at room temperature, and TIC existed in C-added alloys. The grain size was decreased with carbon content due to grain boundary pinning. Texture measurement revealed that strong {112}(beta)< 110 >(beta) recrystallization texture was formed in C-free alloy and that weak {001}(beta)< 110 >(beta) texture in C-added alloys. Tensile tests revealed that clear superelasticity appeared in C-free alloy but that stress-induced martensitic transformation seems to be suppressed by TIC in C-added alloys. The critical stress for slip was linearly increased by carbon content Then, carbon addition affects the shape memory properties of TiNb alloys, and is effective to enhance the critical stress for slip.