Microstructure, texture and phase transformation of Ni47Ti44Nb9 shape memory alloy cold-rolled tube

The microstructures, textures and phase transformations in forged bar, hot-extruded tube, and cold-rolled tubes at different heat-treated conditions of Ni47Ti44Nb9 alloy were investigated by OM, DSC and XRD. The results show that 132 phase in the forged rod has broad fibred shape, and main textures are close to {112} < 111 > and {123} < 111 >; Fibred microstructure in the hot-extruded tube is refined, and the orientations of many grains are close to {111} < UVW >; B2 phase fibres in the cold-rolled tube have been heavily broken, which restrains martensitic phase transformation during cooling, and {111}< 110 > and {112} < 110 > become the major textures. With the increase of quenching temperature, hardness of the cold-rolled tube decreases, M. and A. points increase, thermal hysteresis drops. The above textures in the cold-tube annealed at 600 V for 90 min markedly enhance. When the annealing temperature is 850 V, the recrystallized grains in the cold-rolled tube obviously grow, M,, point markedly increases, thermal hysteresis and hardness decrease, the main textures depart from {111} < 110 > and {112} < 110 >.