B19-phase transition and related tensile properties of Ti50Ni30Cu20 shape memory alloy doped with hydrogen:

The B19-phase transition and the related tensile properties of Ti50Ni30Cu20 shape memory alloys were investigated after hydrogen doping. The results revealed that the presence of hydrogen suppressed the B2–B19 transition by decreasing transformation enthalpies. Aging at room temperature lowered martensitic transformation temperature, which might have been associated with the variation of hydrogen contents and states. Ti50Ni30Cu20 shape memory alloys manifested high thermal cycling stability after the aging treatment. In addition, the increase in the hydrogen content was accompanied by an increment in detwinning stress of B19 phase, whereas the elongation of Ti50Ni30Cu20 alloys decreased. Based on our analysis, these effects were caused by the combined activities of different hydrogen states, including those of hydrides and solid-solution hydrogen.