Temperature induced strengthening in TiNiCuNb shape memory alloy

Mechanical behavior of two-phase (Ti54Ni34Cu12)90Nb10 alloy with B2–B19–B19’ martensitic transformation types was studied by tensile test in wide temperature range. A temperature-dependent stress diagram was obtained based on experimental data, from which the influence of temperature on the different critical stresses was determined. It was shown that the increasing in testing temperature leads to the increasing in dislocation yield of martensite and ultimate fracture stresses, while the dislocation yielding stresses of austenite are stabilized. It was proposed that the phase hardening caused by difference in thermal expansion coefficients between B19 and β-Nb phases may be a possible reason for the temperature induced strengthening. High dislocation density near B19/β-Nb interface supports this assumption.