CU-CONTENT DEPENDENCE OF SHAPE MEMORY CHARACTERISTICS IN TI-NI-CU ALLOYS

Cu-content dependence of the shape memory characteristics in Ti-Ni-Cu alloys has been investigated by means of electrical resistivity measurements, differential scanning calorimetry and constant load thermal cycling tests. Transformation start temperature for the B19' martensite, M(s), decreased largely, whereas that for the B19 martensite, M'(s), increased slightly with increasing Cu-content. Thus, the temperature range over which the B19 martensite was stable became wide. The maximum recoverable elongation associated with the B2-->B19 transformation decreased from 3.2 to 2.7%, and the hysteresis associated with the transformation decreased from 11 to 4 K with increasing Cu-content from 10 to 20 at%. The temperature dependence of stress required to induce the B2-->B19 transformation was nearly constant (about 8 MPa/K) without regard to the Cu content for the alloys with above at% Cu. The residual elongation decreased with increasing Cu content.