Strengthening and Embossment of Final Shape in NiTi Shape Memory Alloys (SMA)

Shape memory alloys transform at low temperature by a martensitic reaction β → α , which implies formation of a domain structure (similar to ferromagnetic, ferroelectric transformations). This microstructure allows complex pseudo‐plastic deformability. A systematic approach is provided for the types of reverse reactions α → β, which are found between crystalographically reversible (martensitic) and diffusion controlled (combined reactions). Features of optimum microstructures for shaping and desired SM‐properties are discussed.