| Shape memory characteristics of thermo-mechanically treated Ti-Ni-Cu alloys have been investigated by means of thermal cycling test under constant load, and then compared with those of solution treated ones. Transformation occurs in one stage, i.e., B2-B19 in the solution treated Ti-49Ni-1Cu(at%) alloy irrespective of the amount of applied stress, while in two stages, i.e., B2→R→B19` in the thermo-mechanically treated one under the applied stress less than 120 MPa, above which in one stage. i.e., B2→19`. In the Ti-46Ni-4Cu(at%) alloy, however, transformation occurs in one stage, ie., B2→B19` in both the thermo-mechanically treated and solution treated conditions. The transformation hysteresis associated with the B2↔B19` transformation increases with increasing applied stress in the solution treated alloys, while almost keeps constant in the thermo-mechanically treated alloys. The critical stress for slip deformation and the maximum recoverable transformation elongation increased largely by applying the thermo-mechanical treatment to the solution treated Ti-Ni-Cu alloys. |
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