Evaluation of fatigue behavior of cast and ultra-fine processed Al-7075 by using friction stir technique

This paper presents experimental results on the fatigue properties of the modified microstructure of cost Al-alloy 7075 via friction stir processing (FSP). The microstructural behavior was investigated by using optical microscope (OM). The grain size of cast FSP-ed at different locations was investigated via XRD. Uniaxial tensile and bending fatigue tests were carried out at room temperature on both cast and after FSP conditions. Fatigue properties were investigated using a fully reversible bending testing machine. Significance enhancement of mechanical properties was attributes to the elimination of porosities as well as uniform distribution of ultra-fine grains throughout the matrix. A fractographic study was done to understand the fracture behavior being changed from quasi-cleavage fracture to dimple fracture. The resultant ultra-fine grain structure causes significant increasing in tensile and fatigue properties.