Friction-Stir-Welded Lap Joint of Aluminum to Zinc-Coated Steel

Abstract

Table 1 Chemical composition of the aluminum base metal 1100H24 (mass %). retracted while the tool continued to turn.The surface for the observation of microstructure was etched by 3% Nital to reveal the steel microstructure and subsequently by 1% HF aqueous solution to reveal the aluminum microstructure.The microstructure was observed with an optical microscope and SEM (Scanning Electron Microscope) for closer observations. A peel test was employed to estimate the fracture load of the obtained joint. The schematic view of the specimen for the peel test is shown in Fig. 4.Temperature measurements at positions close to the zinccoated steel surface (0.3 mm down from the surface) were carried out by using a thermocouple (K-type) percussion-welded to the bottom of holes drilled from the back surface of the steel specimen. X-ray diffraction analyses were carried out to identify phases present on the fracture surfaces of joint after peel tests.

Effect of pin length on Friction Stir Spot Welding (FSSW) of dissimilar Aluminum-steel joints

“…This clearly suggests that the heat and pressure generated by the FSSW process are sufficient to promote diffusion bonding between the aluminum and steel sheets. It has been previously shown that when friction stir spot welds are made in Al/St lap joints, the presence of lower melting point coating on the steel appears to promote higher joint strengths and increased bonded areas (Elrefaey et al (2005) and Miyawa et al (2008)). A key feature of the coating is that the formation of an iron oxide is inhibited, and thus mutual inter-diffusion is promoted which may also facilitate the formation of IMC (i.e.…”

“…Zn coated) in the automotive body industries shows an increasing trend in the last two decades thanks to enhanced vehicle structure durability. It has been proposed that Zn acts as a ''lubricant'' during friction stir lap welding by diffusing into the aluminum sheet and suppressing the melting point of the stirred material so that larger areas can be bonded (Elrefaey et al (2005)). In a further study, Miyagawa et al (2008) noted that the FSW Al joints with Zn coated steel exhibited considerably higher fracture load as compared with those involving uncoated steel.…”

“…Elrefaey et al (2005) reported that the performance of dissimilar aluminum/steel joint depends heavily on the penetration depth of the pin tool into the surface of the lower steel sheet. All these studies noted that when the tool slightly runs into the steel surface, the joint strength is greater than that when the probe tip does not reach the steel surface.…”

Microstructure and Joint Strength of Friction Stir Spot Welded 6022 Aluminum Alloy Sheets and Plated Steel Sheets

“…These works suggested the existence of the plated layer significantly improved their weldability. [8][9][10] The previous reports, however, did not mention the reason why the plate metals could improve the weldability and the behavior of the plated layers during FSW and FSSW operation.…”

Effects of probe tip position on microstructure and bonding strength of friction stir welded aluminum alloy/steel lap joint

“…12 Crack growth behavior at the joint interface during the shear test for the Al/Fe lap joint welded by "ϩ0.1 mm" condition. Two enlarged pictures show the Al/Fe interface "before" and "after" the first load drop.…”