Transformation and superelastic characteristics of large hysteresis TiNi matrix shape memory alloys reinforced by V nanowires

In this work, two TiNiV alloys with nominal compositions of Ti46Ni44V10 and Ti37Ni38V25 were prepared by casting. Thin wires were acquired by cold drawing. The microstructure, transformation characteristics and mechanical properties of the wires were investigated. The microstructure analysis showed that β-V phase was stretched into nanowires after drawing. The results suggested that the R → B19′ transformation increases with increasing annealing temperature. The tension test showed that after 400 °C annealing, the two alloys exhibited superior superelastic. Both of the alloys exhibit high transformation critical stress and large hysteresis. The Ti46Ni44V10 alloy exhibited critical transformation stress of about 575 MPa and reversible strain of about 7% in 8% superelastic cycle. The Ti37Ni38V25 alloy exhibits critical transformation stress of about 1100 MPa and reversible strain of about 6% when annealed at 400 °C. Ti37Ni38V25 alloy exhibited high absorbed energy of about 54 MJ/m3 in 8% superelastic cycle, which is about 3 times higher than that in the NiTi alloy.