The main drawback of friction stir welding (FSW) dissimilar metals is the formation of intermetallic compounds (IMCs), which are brittle and affect the strength of the joint. The formation of these compounds is inevitable due to their low enthalpy of formation; however, their emergence is an indication of metallurgical bonding between dissimilar metals. This means that the determining factors of intermetallics should be optimal to ensure the formation of the joint and, at the same time, the performance of the joint. It is known that various parameters such as welding parameters, joint configuration, and tool geometry have an influence on the formation of these compounds. However, the influence of the base metal is not adequately addressed in the literature. The current review paper focuses on intermetallic formation during the friction stir welding of aluminum/steel (Al/St) alloys to explore how the types of alloys affect the thicknesses and morphologies of the intermetallics. Different structural steels and stainless steels were considered to see how they affect intermetallic formation when welded to different types of aluminum alloys. The thicknesses of the IMCs in the FSW of different aluminum/steel alloys were taken from the literature and averaged to provide insight into the contribution of the elements to IMC formation. Thermodynamic and kinetic analyses were used to explain this effect. Finally, the mechanism of intermetallic formation is explained to provide a useful guide for selecting dissimilar metals for welding using friction stir welding.

Additive manufacturing of acrylonitrile butadiene styrene (ABS) was investigated based on statistical analysis via an optimization method. The present article discusses the influence of the layer thickness (LT), infill percentage (IP), and contours number (C) on the maximum failure load and elastic modulus of the final product of ABS. ABS is a low-cost manufacturing thermoplastic that can be easily fabricated, thermoformed, and machined. Chemical, stress, and creep resistance is all excellent in this thermoplastic material. ABS combines a good balance of impact, heat, chemical, and abrasion resistance with dimensional stability, tensile strength, surface hardness, rigidity, and electrical properties. To comprehend the impact of additive manufacturing parameters on the build quality, both artificial neural network (ANN) and response surface method (RSM) were used to model the data. The main characteristics of the build considered for modeling were ultimate tensile strength (UTS) and elastic modulus. Main effect plots and 3d plots were extracted from ANN and RSM models to analyze the process. The two models were compared in terms of their accuracy and capability to analyze the process. It was concluded that though ANN is more accurate in the prediction of the results, both tools can be used to model the mechanical properties of ABS formed by 3D printing. Both models yielded similar results and could effectively give the effect of each variable on the mechanical properties.

The substitution of traditional materials with lightweight materials in vehicle structures requires the development of new joining techniques which are capable of joining un-weldable alloys as well as dissimilar materials. Although conventional joining techniques such as fusion welding, adhesive bonding and mechanical fastening have matured in recent decades, their use for some of the above applications is limited. In this paper, recently developed joining techniques based on plastic deformation are presented and discussed. These techniques are divided into two categories, those based on mechanical interlocking and those based on metallurgical bonding. The first category covers clinching, self-pierce riveting and some innovative joining methods, and the second category covers friction stir welding and its variants. The focus of this study is on process development, process control and monitoring, process modelling, and joint characterization techniques. Finally, the two categories are compared, and their potential is discussed.