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In this article, dissimilar magnesium and aluminum alloys were welded with a Zn interlayer and TiC nanoparticles by friction stir welding. Optimal joining conditions were achieved by a combination of three traverse speeds (30, 45, and 60 mm/min) and constant rotational speeds (1050 rpm). The best microstructure evolution and mechanical properties were achieved for specimens joined at rotational and traverse speeds of 1050 rpm and 45 mm/min, respectively. The grain size decreases as the traverse speed increases from 30 to 45 mm/min due to a reduction in heat input, an improvement in reinforcing distribution, and high intermixing of materials, then increases from 45 to 60 mm/min due to inadequate heat input for recrystallization process. It was shown that the TiC particles play a prominent role in the microstructure modification and enhance mechanical properties of weld samples while the Zn foil interlayer plays a vital in avoiding the formation of Al-Mg IMC phases. The obtained result under optimal welding parameters indicates that MgZn2, Mg-Al-Zn compounds, Mg and Al solid solution, were the main detected common phases in the stir zone instead of the brittle and hard Al-Mg IMCs formation. The average hardness values of 232 Hv were achieved, while the strength of the weld specimen experiences the 189 MPa value. In addition, a combination of brittle and ductile modes was observed based on the fracture surface of the weld sample after the tensile test. [ABSTRACT FROM AUTHOR]

The corrosion behaviour and the influence of nickel and post-weld heat treatment (PWHT) on the susceptibility to corrosion in welded duplex stainless steels were investigated. After PWHT, the amount of nickel for the weld region increases resulting in the generation of austenite and consequently, helping to obtain a favourable ferrite-to-austenite ratio. Comparing the experimental outcomes, it is noticed that the pits initiate and propagate in HAZ indicating this area is more susceptible to corrosion resistance compared to the fusion zone. The pitting resistance equivalent number alone is not sufficient reason to study the complex corrosion phenomenon, and the influence of other parameters namely microstructural evolution on the breakdown of passivity by pitting and the existence of intermetallic phases should be determined together. [ABSTRACT FROM AUTHOR]