Abstract
A pure Ni interlayer with a thickness of 0.1 mm was introduced between high-strength interstitial free steel and Al–Mg–Si alloy, which were friction stir lap welded, producing an excellent welded joint. The interface layer consisted of a γ-Ni solid solution, and the mixed stirring zone contained alternate lamellae of γ-Ni and α-Fe solid solutions. The addition of a Ni interlayer strongly suppressed the reaction between Al and Fe because of the atomic arrangement of Ni. Furthermore, the insertion depth of the stirring pin has a significant influence on the Al/steel interfacial reaction. Under shallow insertion depth, the intermetallic compounds of both FeAl and Fe2Al5 were observed at the interface layer. A maximum tensile-shear fracture load of 4.3 kN was achieved, with fractures being present in the steel substrate far away from the Al/steel weld.
Highlights
In the automotive industry, welding Al alloys to steel has important implications for reducing the weight of the vehicle [1]
The enhancements in bonding properties of the Al/steel joint were relatively limited, because the brittle and hard Al–Fe intermetallic compounds were difficult to avoid during the higher heat input conditions of fusion welding, which could be a source of cracking
Kimapong et al [9] carried out friction stir lap welding (FSLW) of 5083 Al alloy to lowcarbon steel, and studied the effects of welding parameters on the mechanical properties of the weld
Summary
In the automotive industry, welding Al alloys to steel has important implications for reducing the weight of the vehicle [1]. The enhancements in bonding properties of the Al/steel joint were relatively limited, because the brittle and hard Al–Fe intermetallic compounds were difficult to avoid during the higher heat input conditions of fusion welding, which could be a source of cracking. Recent studies [11,12,13,14,15] indicated that besides FSW parameters such as welding speed, rotation rate and tool position, the bonding of the steel/Al interface is closely related to the Al/steel interfacial interlayer or steel surface coating. Based on the above studies, it can be concluded that coatings or interlayers with lower melting points find it difficult to suppress the diffusion between Fe and Al. introducing an interlayer material that can effectively suppress diffusion between Fe and Al and provide the desired mechanical properties is important, in order to obtain an excellent Al/steel joint. The influences of the Ni interlayer on the microstructure and mechanical properties of the FSLW Al/steel joint were studied
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