Fatigue behaviour at elevated temperature of friction stir channelling solid plates of AA5083-H111 aluminium alloy

Friction stir channelling (FSC) is an innovative solid-state manufacturing technology able to produce continuous internal channels in a monolithic plate in a single step that can be used to produce conformal cooling/heating systems. During FSC a controlled amount of workpiece material flow-out from the processed zone producing the internal channel. The heat energy that softens the workpiece material is generated from dissipation during plastic deformation, internal viscous dissipation during the material flow and dissipation from frictional work between the tool and the workpiece. The purpose of this study is to investigate the fatigue behaviour of friction stir channelling specimens at elevated temperature. Fatigue tests were carried out at room temperature, 120 °C and 200 °C in a servo-hydraulic testing machine coupled with a furnace. The specimens were tested until fracture or up to 3 × 106 cycles. It was found that the fatigue resistance is dependent on the testing temperature. The results indicated that the fatigue life of an aluminium alloy friction stirred channel was reduced with increasing the testing temperature. Based on the fracture surfaces observations, the developing fatigue-crack always initiated at the advancing side, namely on the boundary between the nugget and the thermo-mechanically affected zone into the interior of the specimen.