Criteria of transformation sequences in NiTi shape memory alloys

Abstract

Near-equiatomic NiTi alloys are known to exhibit different transformation sequences associated with different thermomechanical treatment and testing conditions. Although a wide range of experimental data has been accumulated through the past few decades of research, there has been a lack of understanding of the thermodynamic criteria for the occurrence of various transformation sequences. This paper presents a phenomenological thermodynamic analysis of the transformation conditions and derives criteria for the sequences, which agree well with experimental observations.