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In this study, friction stir welding joints between dissimilar magnesium and aluminum alloy sheets were made with the addition of TiC reinforcing particles and Zn foil metal interlayer. The impact of process passes on the microstructural behaviors, intermetallic compounds (IMCs), and mechanical characteristics of weld specimens were studied, and the strengthening and toughening mechanism was displayed. It was shown that the TiC particles play a significant role in the microstructure modification and enhanced mechanical properties of weld samples, while the Zn foil interlayer plays a vital role in avoiding the formation of Al–Mg IMC phases. MgZn and MgZn2IMCs, Mg and Al solid solution were the main detected common phases in the stirred zone instead of the generation of the hard and brittle Al–Mg intermetallic. The results indicated that the welding passes significantly influenced the microstructure of the stir zone due to the opposite moving direction of the welding tool between the consecutive passes. The increasing process passes from 1 to 3, noticeably improved homogenized the microstructure and mechanical characteristics of weld specimens due to fine uniform distribution of TiC nanoparticles, improved wettability and plastic flow of materials, and reduction in IMCs formation. This resulted in an improvement in maximum hardness and ultimate strength of weld specimens from 139 to 211 Hv and 118 to 203 MPa as the pass number increased from 1 to 3.

In this article, wear and microstructure behaviors of dissimilar Al–Mg joints made by friction stir welding (FSW) with the addition of TiC nanoparticles under different welding parameters were investigated. Optimal joining conditions were achieved by a combination of various rotational and traverse speeds and the best microstructure evolution, mechanical properties, and tribological behaviors were achieved for specimens joined at rotational and traverse speeds of 850 rpm and 50 mm/min, respectively. It was shown that the TiC particles play a prominent role in the microstructure modification and enhanced mechanical properties of weld samples due to the recrystallization process and pinning effect. The maximum hardness and strength values of 241 HV and 168 MPa, respectively were obtained for the weld sample made by optimal condition. The friction coefficient and wear volume loss for weld samples fabricated at 850 rpm and 50 mm/min is comparatively less compared to other conditions due to the highest grain refinement, homogenous distribution of particles, and highest hardness characteristics. The major wear happened because of adhesion, abrasion, plastic deformation, delamination, and oxidation.

The impact of joining parameters, namely preheat, current, and travel speed, due to the crack formation susceptibility of D2 steel during the deposition process, is crucial to achieve weld bead geometries with acceptable metallurgical and mechanical properties. Therefore, the main purpose of the current article is to optimize welding parameters to obtain a sufficient hardfaced coating of nickel-base powder combined with tungsten carbide on the tool steel by the plasma transferred arc (PTA) process with the help of the Design of Experiment (DoE) method. To analyze the properties of the welding beads, scanning electron microscopy (SEM) accompanied by EDS, optical microscopy (OM), XRD analysis, microhardness, and nano-indentation methods on the samples were applied. The results indicated that there is adequate adhesion and continuous bonding between areas due to improved interactions between hard particles and matrix which leads to a reduction in the porosity of the composite coatings. According to the obtained results, the optimized parameters (current, travel speed, and preheating temperature) for uniform distribution of reinforcing particles and high mechanical properties are 86 A, 85 cm/min, and 1350 °C, respectively. Based on optical profilometry analysis on the surface of the samples, there is high homogeneity in reinforcing distribution. The nanoindentation analysis detected three prominent phases, including FeNiCr dendritic matrix phase, large WCrC (carbide) phase, and mono tungsten carbide WC phase. The obtained results improve the length of the tool's service life and an economic fabrication with decreased unit costs.

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.