Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

Abstract

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material -aluminium -and then the scribe cuts the bottom material -steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features, including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, the influence of zinc coating on joint strength was also studied.

A review on friction-based joining of dissimilar aluminum–steel joints

“…Pin offset in Al leads to major plastic deformation of the Al material while partial deformation of the steel material, which causes the dispersion of steel particles and that consequently lead to mixing of steel particles into the Al matrix. 1,25,55,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] The size of these steel particles are dependent on tool pin offset majorly as well as heat input given by the process parameters of rotational speed, travel speed, and tool design. Another important parameter is the position of the workpiece, 1,53,89,90 wherein, effective material flow and enhanced mixing can be obtained when steel is kept at the advancing side and Al at the retreating side.…”

“…Friction stir scribe welding is a technique developed based on FSW that uses modified tool design to joint workpieces of lap joint configuration. The end surface of the tool pin consists of scribe that is hard material insert with very small length 84,144 as shown in Fig. 8(a).…”

“…Dissimilar joint can be successfully obtained with friction stir scribe welding by inserting the tool pin into the low melting softer material (i.e., kept at top) along with scribe insertion in another material. 84,144 This causes huge plastic deformation at the pin area of the softer material and helps in dispersion of small particles from the bottom material and improves material mixing [see Fig. 8(b)].…”

Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints

“…Different from the conventional FSW of dissimilar materials, the shoulder and pin in FSS do not generate bulk plastic deformation of the higher melting temperature material, and bonding can be formed at a temperature below the melting point of the lower melting temperature material. Recently, a few studies have been reported on FSS joints for different material combinations, such as Al to polymer [19], Al to carbon fiber reinforced polyamide [20], and Al to steel [21,22]. Most studies focus on the continuous mechanical interlock formed at the joint interface, i.e., the hook-like structure, while there is a lack of fundamental understanding on the bond formation mechanism at the bimaterial interface of Al and Fe from an interfacial bond formation perspective.…”

“…Wang et al [22] found an Al-Fe intermetallic region on the fracture surface of the steel side in FSS welded Al to galvanized steel joints, indicating that in addition to the mechanical interlock, interfacial bonding also occurred during the welding process. In this paper, the interfacial microstructure of a typical FSS welded Al to ultra-high-strength steel joint is investigated to analyze the interfacial bond formation mechanism.…”