Figure 6. 𝑆-𝑁 curves of fatigue test results.
Figure 7 shows the fracture surface of the friction stir processed FSWed joint AA6082/AA8011 joints which failed under fatigue loading. The tests were performed using amplitude at 30 % UTS to 80 % UTS on both joints (AA6082/AA8011 and AA8011/AA6082). During each fatigue loading cycle at the highest stress intensity, the crack growth created a band of markings known as striations on the fractured surface and these striations are very useful in determining crack growth direction [40-41]. The striations are evident in Figure 7(a) to (f) , moreover, a cluster of teared dimples were noted in figure 7(b) and in 7(c) few dimples were also observed which are characterization of ductile fatigue fracture [42-43]. Figure 7(a), (e) and (f) also shows particle inclusions as denoted by the doted circles. Figure 8(a) to (e) exhibits the fractographs for the friction stir processed FSWed AA8011/AA6082 joints failed under fatigue loading. In Figure 8(a) to (e) the fractographs all show fine and dimpled micrographs while Figure 8(f) shows a micrograph with fine striations.