Effect of friction stir processing on the fatigue properties of a Zr-modified 2014 aluminium alloy

The fatigue properties of a Zr-modified 2014 aluminium alloy resulting from friction stir processing (FSP) were analysed in the present study. The sheets were processed parallel to the extrusion direction; the tensile mechanical properties were evaluated at room temperature in the longitudinal direction with respect to the processing one in order to observe the differences from the parent material as a function of the strong grain refinement due to the friction stir process. The fatigue endurance (S–N) curve of the FSP material was obtained by using a resonant electro-mechanical testing machine under constant loading control up to 250 Hz with sine wave loading. The cyclic fatigue tests were conducted in the axial total stress–amplitude control mode with R = σmin/σmax = 0.1. The microstructure resulting from the FSW process was studied by employing optical and scanning electron microscopy.