Texture and Its Effect on Shape Memory Properties of Ni 47 Ti 44 Nb 9 Forged Rods

The microstructure, texture, recovery rate and recovery strain of the Ni 47 Ti 44 Nb 9 forged rods were studied. The formation mechanism of texture and its effect on shape memory properties were also discussed. Microstructure were observed through scanning electronic microscope (SEM), texture were analyzed by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD), recovery rate and recovery strain were tested by tube-expansion-recovery method. The results showed that NiTi matrix phase in the Ni 47 Ti 44 Nb 9 forged rods distributed as fibers along the axial direction, while β-Nb phase existed between the fibrous microstructures, which indicated that both NiTi and β-Nb phases had large plastic deformation after forging of Ni 47 Ti 44 Nb 9 alloy. The {111}<110> texture was mainly formed during the forging process of Ni 47 Ti 44 Nb 9 alloy, that was, the axial direction of forging rod was parallel to the <111> direction while the radial direction was parallel to <110> direction. The formation mechanism could be attributed to the fact that during the forging process, Ni 47 Ti 44 Nb 9 alloy was subjected to radial compressive stress, so that the slip surface continuously rotated to the direction perpendicular to compressive stress axis and the slip direction tended to the rheological direction gradually. In addition, {111}<110> texture formed in the forging process of Ni 47 Ti 44 Nb 9 alloy could cause differences in shape memory properties when expanded in different directions. When the expanding direction paralleled to <110> direction, the recovery rate and recovery strain would be 3.52% and 0.62% higher than the case of paralleling to <111> direction respectively. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.