Phase transformation behavior and shape memory characteristics of Ti-Ni-Cu-Mo alloys

Abstract

Phase transformation behavior, the shape memory characteristics and the superelasticity of Ti-Ni-Cu-Mo alloys have been investigated by means of electrical resistivity measurements, X-ray diffraction, thermal cycling tests under constant load and tensile tests. A fully annealed Ti-44.7Ni-5Cu-0.3Mo alloy transformed in two-stage, i.e., the B2-B19-B19′ on cooling and the B19′-B19-B2 on heating. Fully annealed Ti-39.7Ni-10Cu-0.3Mo, Ti-34.7Ni-15Cu-0.3Mo and Ti-29.7Ni-20Cu-0.3Mo alloys transformed in one-stage on, i.e., from the B2 to the B19 on cooling and from the B19 to B2 on heating. The maximum recoverable elongation deceased from 6.0 to 2.4% with increasing Cu-content from 5 to 20 at%. Transformation hysteresis associated with the B2-B19 transformation decreased from 11 to 5 K with increasing Cu-content from 5 to 20 at%. Substitution of Mo for Ni in Ti-Ni-Cu alloys improved the superelasticity.