Abstract
The effect of the martensitic phase transformation in NiTi and CuZnAl alloys on the fatigue behaviour has been investigated. Alloys were prepared with slightly different compositions to provide martensite start temperatures (Ms) ranging from −120°C to + 50°C, and these were tested at room temperature. For NiTi, decreasing7Ms leads to an initial increase and then a decrease in both the 10 cycle fatigue limit and low cycle fatigue total strain at a given number of cycles to failure. In contrast, CuZnAl alloys in the martensitic condition showed longer fatigue lives and higher strains in low cycle fatigue although all CuZnAl alloys showed orders to magnitude shorter fatigue lives than NiTi alloys at comparable stresses. It is concluded that the exceptionally large strains observed in low cycle fatigue of NiTi alloys are a consequence of reversible martensite deformation processes inhibiting crack nucleation.
Published Version
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