Structure and substructure characterization of solution-treated Ni50.3Ti29.7Hf20 high-temperature shape memory alloy

We investigate the structure and substructure of solution-treated martensitic Ni 50.3 Ti 29.7 Hf 20 high-temperature shape memory alloy (SMA) by transmission electron microscopy precession diffraction (PED). Most martensite plates contain high-density internal (0 0 1) compound twins. Four variants (i.e., A, B, C , D ) were observed using PED. The orientation relationships determined to be (1 1 0.64) Type II twins between A B I D. are divided junction planes, in which is parallel . These rarely other NiTi or NiTiHf SMAs, offers new insight understand phase transformation behavior SMAs. Several low-angle grain boundaries near variant interfaces, may explain difficulty reorientation detwinning