In the previous work, Horibe, one of the authors of this study, indicated that in the AZ31 magnesium alloy, the twinning-detwinning process dominated the plastic strains with greater amplitude, whereas dislocation slips dominated the lower plastic strains, which appeared bi-linear in the Manson-Coffin curve (M. Matsuzuki, S. Horibe, MSEA 504 (2009) 169-174). This alloy is used in a fatigue environment after plastic forms. However, the influence of pre-compression on either the fatigue life or deformation mode (slip or twinning) has not been clarified. In this study, we demonstrate that through pre-compression, more twinning tends to change the S- N curve from bi-linear to linear by changing the deformation mode, which results in shortening the fatigue life at lower stress levels. Furthermore, pre-compression promotes natural aging and increases yield stress. Higher yield stress increases the remaining twinning after the first fatigue test cycle, which also decreases the fatigue life.
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