Effect of stress ratio on the fatigue behavior of a friction stir processed cast Al–Si–Mg alloy

The effect of friction stir processing (FSP) on the fatigue life of a cast Al–7Si–0.6 Mg alloy at stress ratios of R = 0 and R = −1 was evaluated. Two types of specimen geometry were used for the FSPed condition, through thickness processed and partial thickness processed. At R = 0, the microstructural refinement enhanced the fatigue life by a factor of 15, whereas at R = −1 the improvement in fatigue life was 5-fold. In light of these observations, various closure mechanisms were examined.