Sharif Digital Repository

Dissimilar joining of aluminium and steel, especially using resistance spot welding as a critical process in vehicle manufacturing, is a key challenge for multi-materials lightweight design strategy. Controlling the formation and growth of Al5Fe2 intermetallic is the outstanding issue for producing high strength crash-resistance Al/steel dissimilar resistance spot welds. This critical assessment highlights the current understating regarding factors affecting the joint properties and approaches to control the interfacial reaction. Finally, the unresolved scientific challenges are discussed with the goal of shedding light on the path forward to produce reliable metallurgical bonding between... 

We studied the microstructure and mechanical characteristics of spot welded specimens, fabricated from low carbon steel sheets with different microstructures. Both ultra-fine grained (UFG) steel sheet and coarse grained (CG) steel sheet were used. The refined microstructure of the UFG steel has been produced by severe plastic deformation (SPD) using the constrained groove pressing (CGP) method. The grain size of the base metals was approximately 260. nm and 30. μm in diameter, respectively, in the UFG and CG steels. Examining the microstructure of a cross section cut through the spot weld reveals a similar grain size and phase distribution in the nugget on both the sides of the initial... 

Friction stir welding (FSW) of dissimilar joints has recently attracted great interest for the fabrication of bimetallic and layered composite structures. In this paper, dissimilar joining of an aluminum-matrix hybrid nanocomposite to commercial pure aluminum is reported for the first time. An aluminum hybrid nanocomposite reinforced with Al2O3 (2 vol%; 15 nm) and SiC (2 vol%; 50 nm) nanoparticles was prepared by powder metallurgy routes including mechanical milling and hot powder consolidation techniques. Different joint designs at various ranges of rotational (w) and traverse velocities (v) were evaluated to determine process window for the dissimilar solid-state welding. Macro- and... 

In this research, the feasibility of friction-stir welding (FSW) for dissimilar lap-joining of an aluminium-magnesium alloy (AA5058) and poly-methyl-methacrylate sheets to attain sound and defect-free joints was examined. The inter-mixing flow patterns between the metal and polymer counterparts during FSW were predicted by employing three-dimensional finite element models. It is shown that the bonding mechanism between the dissimilar materials is mechanical interlocking at the interface which controls the joint strength depending on the processing parameters. The most suitable dissimilar lap-joining regarding microstructural soundness is attained at w= 1600 rev min−1 and v = 25 mm min−1.... 

We present a new semi-solid state procedure for efficient joining of dissimilar materials. The process called fed friction stir processing (FFSP) and works based on in-situ injection of colloidal nanoparticles in the welding line during processing. To present the efficiency of the process, friction stir welding of AA6062 aluminum alloy and poly(methyl methacrylate) (PMMA) through injection of alumina nanoparticles is presented. Microstructural features and mechanical characteristics of the weldments are elaborated. It is shown that in-situ feeding of the alumina nanoparticles during FFSP changes the thermo-mechanical regimes of the bonding zone and decreases the thickness of interaction...