J. Phys. IV France 112 (2003) 697
Shape memory behavior associated with a two-stage R-phase transformation in Ti-50.9at%Ni alloyJ.I. Kim and S. Miyazaki
Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
It was first found by the present authors that a two-stage R phase transformation appears in a Ti-50.9at%Ni alloy aged at 473K. The two-stage R phase transformation is characterized by two DSC peaks prior to the martensitic transformation during cooling (the first R phase transformation on cooling is denoted by R 1 and the second by R 2). Transformation temperatures of both the R-phases, R 1 and R 2, increase with increasing aging time. According to thermal cycling tests under various constant stresses, transformation strain of R 2 is larger than that of R 1, With increasing applied constant stress, the latter strain increases and the former one decreases. However, total strain of both R 1 and R 2 is almost constant irrespective of stress.
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