| Shape recovery stress of Ti-50.2Ni and Ti-(50-X)Ni-XCu(at%)(X=5-30) shape memory alloys has been measured by means of thermal cycling tests under constant load. In each alloy, the shape recovery stress increased with increasing applied stress up to the critical stress for slip deformation, above which it decreased with increasing applied stress. This was due to decrease in recoverable elongation by the slip deformation. The critical stress for slip deformation depended on Cu-content. With respect to the maximum shape recovery stress, for the alloys whose Cu-content was less than 5at% and more than 15at%, it decreased with increasing Cu-content. For the alloys whose Cu-content was between 5at% and 15at%, however, it increased with increasing Cu-content. Cu-content dependence of the maximum recovery force did not correspond to that of recoverable elongation. Thermal cycling test under costant load method was effective to measure a heating temperature dependence of the shape recovery stress. |
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