Grain size effect on low cycle fatigue behavior of copper polycrystals

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Liu, Wei
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The absence of complete and reliable results on the effects of the grain size on the cyclic behavior for polycrystalline copper determines the main objective of the present study, which was conducted in an attempt to address the reason for the existing scatter in the literature. The grain size effect on low cycle fatigue (LCF) behavior of copper polycrystals was studied at room temperature under symmetric tension-compression cycling at constant total strain amplitude control with a low constant plastic strain rate. Sets of specimens with different grain sizes were cyclically tested, over a range of plastic strain from 5 * 10-6 to 5 * 10-3, up to saturation. The obtained saturation stresses were plotted as a function of corresponding plastic strain amplitudes to obtain a cyclic stress strain curve (CSSC) for each grain size. Finally, all the cycled specimens were sectioned and cut longitudinally in the mid-section of the specimens to produce samples for microscopic investigation. Scanning electron microscopy(SEM) was conducted on the etched samples for the evidence of persistent slip bands (PSBs). (Abstract shortened by UMI.)