Influences of roughness and heat treatment on high-cycle bending fatigue of A380 aluminum alloy under stress-controlled cyclic loading

Abstract In the present study, the effect of the T6 heat treatment on high-cycle bending fatigue properties of the A380 (AlSiCu) aluminum alloy has been investigated. The fracture behavior of materials was also examined under stress-controlled cyclic loadings. For such an objective, standard specimens were prepared and tested by a rotating bending fatigue machine. In addition, the microstructural characterization and the fracture surface analysis were performed by the scanning electron microscopy. Using the T6 heat treatment, the solution treatment was performed at 510°C for 5 hrs and after quenching in the air, the ageing treatment was carried out at 200°C for 3 hrs. The main aim of this work is to investigate the heat treatment effect on fatigue properties of AlSiCu alloys. Moreover, the roughness influence was also studied on the fatigue lifetime. Based on experimental results, the heat treatment changed the distribution and the size of silicon phases and enhanced the microhardness. Under the highest and lowest stress levels, the heat treatment increased the high-cycle bending fatigue lifetime by 26% and 85%, respectively. Samples with low roughness had a greater fatigue lifetime than those with high roughness. The fracture surface analysis demonstrated that in both as-cast and heat-treated specimens, several microcracks occurred through intermetallic compounds. The heat-treated and as-cast materials showed a brittle fracture behavior due to cleavage planes on the fracture surface of specimens. However, some dimples and quasi-cleavages were also observed on the fracture surface of as-cast samples.