Martensitic transformation in TiPd shape memory alloys studied by PAC method with 181Ta probes

Perturbed angular correlation (PAC) method was applied to study the martensitic phase transition of the TiPd shape memory alloy doped with 181Hf/181Ta probe atoms. The hyperfine interaction parameters and their concentration and temperature dependences for probes with cubic and noncubic surroundings of the lattice sites, consistent with the respective crystal structures in martensite and austenite phase, were determined. A strong dependence of the martensite start temperature (MS) and the shape of the hysteresis loop (TH) on the small admixture of the Hf impurities in TiPd compound were evidenced. The observed decrease of the MS value differs from the behavior of TiNi alloy, where adding hafnium as the third element leads to a rise of MS.