Recovery and recrystallization processes in TiPdNi high-temperature shape memory alloys

Abstract

The TiPdNi alloys are promising high temperature shape memory alloys. To improve the high temperature shape memory characteristics, a proper thermomechanical treatment is useful, and the understanding of recovery and recrystallization processes is important in this context. For this purpose, the recovery and recrystallization processes in the alloys were studied in detail by micro-Vickers hardness test, differential scanning calorimetry and transmission electron microscopy. As a result, a close relationship was found between the recovery, recrystallization and the reverse transformation of the alloys, and the relationship was explained by a large difference in diffusion rate in the parent and in the martensite. This result indicates that the recovery and recrystallization in the present alloys are controlled by the reverse transformation temperatures of the present alloys. Other features of the softening in hardness are discussed in detail based on electron microscopy observations.