Effect of Annealing on High-Cycle Fatigue of an Al-Mg-Sc Alloy Produced by Equal-Channel Angular Pressing
Chihiro WATANABE, Ryoichi MONZEN and Kazue TASAKI
Abstract:The effect of short time annealing on the high-cycle fatigue behavior of an ultrafine grained Al-Mg-Sc alloy produced by equal channel angular pressing (ECAP) has been studied. Transmission electron microscopy revealed that small Al3Sc precipitate particles initially restricted grain growth and then the Al3Sc particles coarsened, allowing homogeneous grain growth during annealing at 350oC. The as-ECAP specimen exhibited high tensile strength, but low ductility. The annealed ECAP specimens showed slightly smaller values of 0.2% proof stress and ultimate tensile stress, and fairly larger values of elongation to failure than the as-ECAP specimen. In the as-ECAP specimens, cyclic softening was observed, whereas the annealed ECAP specimens exhibited no cyclic softening. The existence of Al3Sc particles produced by the annealing enhanced the uniform deformation and the absence of cyclic softening in the annealed ECAP specimens. These resulted in increase of remarkably prolonged high-cycle fatigue lives in comparison with the as-ECAP specimen. Key Words:Al-Mg-Sc alloy, Equal-channel angular pressing, Al3Sc precipitates, High-cycle fatigue