h. vahid

In the last two decades, friction stir processing (FSP), as one of the prominent severe plastic deformation methods, has received much attention from researchers due to its unique advantages. However, so far there has been no study on the behavior of the FSPprocessed materials in the presence of cracks. So, this work investigated the mixed-mode (tensile-shear) failure, mechanical, and microstructure properties of the FSP-processed 6061 aluminum alloy, utilizing the essential work method of fracture. According to the tensile test, both the yield and ultimate tensile strengths of the processed sample showed an increase of 47% and 67%, respectively, due to the intensive grain refinement (57% reduction in grain size). Based on the fracture test, the essential work of fracture in the processed sample was 11 kJ/m2, which is 33% less than that of its initial annealed counterpart. Therefore, while the friction stir processing can substantially improve the mechanical strength of the 6061 aluminum alloy, its fracture toughness has significantly decreased.