Mean stress sensitivity of the fatigue strength after equal-channel angular pressing of the aluminum alloys 6082 and 6060

Abstract

The present study is focused on the influence of equal-channel angular pressing (ECAP) on the mean stress sensitivity of the fatigue strength. Systematic work has been done comparing the two precipitation-hardening aluminum alloys 6082 and 6060 in peak-aged and ECAP-processed condition, respectively. The fatigue strength was determined at alternating compression-tension and tension stresses with load ratios of R =-1, 0 and 0.1. Both aluminum alloys in peak-aged condition exhibit a strong dependence of the fatigue strength on the load ratio; i.e. and therefore on the applied mean stress. An increase in load ratio, which implies an increase in mean stress, results in a decrease of the fatigue strength amplitude. In contrast, ECAP-processing neutralizes the mean stress sensitivity of the fatigue strength for both aluminum alloys. The fatigue strength for the ECAP-processed conditions is not influenced by the load ratio: The fatigue strength amplitudes at tension mean stresses (R = 0 and 0.1) are just as high as for zero mean stress at alternating compression-tension stresses (R =-1). The neutralization of the mean stress sensitivity of two aluminum alloys due to ECAP-processing is shown for the first time in this study.