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In this study, dissimilar joints of AA5083-H116 and AA7075-T6 aluminum alloys were successfully made by friction stir welding technique. The microstructure and mechanical behavior of the welded joints were investigated at different rotational and traverse speeds. A mathematical modeling was developed to demonstrate a relationship between the friction stir welding parameters and the ultimate tensile strength of the dissimilar joints. Then, the mathematical modeling was optimized by genetic algorithm in order to find the optimum condition in which the maximum tensile strength of welded joints can be achieved. Eventually, genetic algorithm results confirmed that the maximum tensile strength of welded joints is achievable in rotational and traverse speeds of 500 r/min and 50 mm/min, respectively. The maximum error between experimental data and predicted model was less than 1%.

The aim of this study is to investigate the effect of adding Al 2 O 3 nanoparticles on the properties of joints fabricated by friction stir welding. The joints were characterized by optical microscopy, scanning electron microscopy, dry sliding wear test, and potentiodynamic polarization test. The results show that the average grain size was reduced in the nugget zone after the addition of nanoparticles. The produced welds were also found to have adequate wear and corrosion resistance. This work demonstrates that adding Al 2 O 3 nanoparticle is an effective strategy for improving the properties of the joints produced by friction stir welding.

This paper aimed to propose a novel bulk plastic deformation method entitled hydrostatic backward extrusion process that is an implementation of the benefits of hydrostatic extrusion to the backward extrusion process. The applicability of the process was investigated using experimental tests and finite element analysis. The results showed that the produced tube by hydrostatic backward extrusion exhibits higher effective plastic strain while needing lower process load (elimination of friction force). The maximum process load in hydrostatic backward extrusion was obtained 55 kN that was 61.1 and 264.6 kN in the novel method of backward extrusion and conventional backward extrusion processes, respectively. This new method is promising for processing of high-strength ultrafine-grained tubes and hard-to-deform materials because of the nature of the processing by hydrostatic pressure.

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