SHAPE-MEMORY BEHAVIOR OF TI-40.5NI-10CU ALLOY AFFECTED BY C11(B)-TYPEPRECIPITATES

Effects of precipitates of C11(b)-type structure formed by aging on th e mechanical properties of a shape memory Ti-40.5Ni-10Cu alloy, which slightly off-stoichiometric to the Ti poor side, were studied by const ant-load thermal cycling tests, conventional tensile tests and transmi ssion electron microscopy. The shape change under a constant load, ass ociated with thermally induced B2-B19 transformation, occurs in narrow er temperature range for both the cooling and heating processes in the fully aged specimen compared to the as-solution-treated specimen. The total elongation due to thermally induced B2-B19 transformation under a constant load decreases and the 0.5% offset stress in the conventio nal tensile test increases with increasing aging lime. These aging eff ects on mechanical properties are caused by the precipitates of C11(b) -type structure. The precipitates act as obstacle to the rearrangement of variants of the B19-martensite.