Investigation on effects of traverse speed and number of passes on mechanical and abrasive properties of AA7075-T6/ZrO2 surface nanocomposite produced using friction stir processing

In this study, a AA7075-T6/ZrO2 nanocomposite was successfully fabricated. The effects of the traverse speed and the number of passes on mechanical properties were evaluated. For this purpose, after examining the external surfaces of the samples, various test samples were extracted. Metallographic samples were first investigated with a stereomicroscope and an optical microscope. Then for more details, such as observing grains with higher resolution and distribution of nanoparticles in the matrix, the samples were studied with an electron microscope. XRD and EDS analyses were also performed to evaluate the formed phases. For a more detailed study, metallographic samples were used for the microhardness test. Tensile tests were performed to assess nanocomposites' yield and tensile strengths and to compare them with those of the base metal. Then, the fracture surfaces were examined under an electron microscope to observe and evaluate different aspects of fracture surfaces. Finally, an abrasion test was performed to assess the wear rate of nanocomposite samples and compare them with the base metal. Two main factors of grain and agglomeration sizes play important roles in the mechanical and wear properties. The Mean and max microhardness of the base metal was increased by 31.3% and 44% by nanocomposite production, respectively. Even though the tensile properties such as yield and tensile strength decreased compared to the base metal, they are better with a long-distance than annealed condition. Also, the wear rate in sample 30-1, which had minimum grain and agglomeration size, decreased up to 67% compared to the base metal.