Fatigue life cycle
Figure 6 shows the stress –number of cycles to failure curves for the AA6082/AA8011 and AA8011/AA6082 friction stir processed FSWed joints. The AA8011/AA6082 joint had a fatigue life of 4.489×105 while the AA6082/AA8011 had a a life span of 1.765×106. The AA6082/AA8011 had a longer fatigue life cycle compared to the AA8011/AA6082 joint and similar behaviour is alos found in the literature [37-39]. The fatigue life behaviour was found to be in agreement with the findings by Park et al. [20], which reports that the fatigue life increases as the microstructural grains decreases.