On the lattice parameters of phases in binary Ti–Ni shape memory alloys

Abstract An X-ray diffractometry study of Ti–47.0 to 50.7 at.%Ni alloys was performed. In the 50.0–50.7 at.% range of nickel content, a concentration dependence of B19′-martensite lattice parameters (MLP) is observed. MLP are found to be identical for 47.0 and 50.0 at.% of nickel content. The temperature dependence of MLP is observed, and this dependence is enhanced in the reverse transformation temperature range for Ti–50.0 at.%Ni alloy. MLP are different for the quenched martensite and for the martensite formed from the austenite containing a well-developed dislocation substructure. It is proven that the presence of an intermediate R-phase during martensitic transformation is not responsible for the changes in MLP, observed in hyper-equiatomic alloys or in alloys having a highly dislocated austenite substructure. In the 50.0 at.%Ni alloy, no changes in MLP are observed after a 25% cold-deformation of the already formed thermal martensite.