Local fatigue and wear behaviours of 7075 aluminium alloy induced by rotational fretting wear

Rotational fretting (RF) wear tests of 7075 aluminium alloy were conducted and the local fatigue and wear behaviours were analysed. Results showed that the cracks initiated at the contact edge and propagated along a sharp angle (∼15° to 30° with respect to the base alloy) in the mixed fretting regime (MFR). However, only some delamination induced by the parallel cracks can be observed in the partial slip regime (PSR) and the slip regime (SR). In MFR, the rate of crack propagation was higher than that of wear, and thus the local fatigue dominated the competition between fretting-induced wear (FIW) and fretting-induced fatigue (FIF). For RF, it was a unique phenomenon that protrusion was generated at the contact centre due to the plastic-flow accumulation of materials, which also indicated that the initiation of fatigue crack may be closely related to the central protrusion, and the protrusion played an important role in controlling the local fatigue behaviour. In addition, the friction-dissipated energy method can be used to characterise the running behaviours of RF.