Effect of Annealing Temperature on Microstructure and Shape Memory Characteristics of Ti–22Nb–6Zr(at%) Biomedical Alloy

Effect of annealing temperature on microstructure and shape memory characteristics of Ti–22Nb–6Zr(at%) biomedical alloys was investigated by using tensile tests, XRD measurement, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After severe cold-rolling, the plate was annealed at temperatures between 773 and 1173 K. The (alpha)/(beta) transus temperature in this alloy was determined to be between 823 and 873 K. The specimen annealed at 823 K for 3.6 ks exhibited a fine subgrain structure. A fully recrystallized structure was observed in the specimens annealed above 873 K. The annealing temperature less affected the transformation temperature and recovery strain. However, the critical stress for slip decreased considerably with increasing annealing temperature, because the grain size increased. All specimens annealed above 823 K exhibited stable superelastic behavior at room temperature.