Dissimilar metal joining of aluminum alloys to steel is generally difficult to be in practical use because of a formation of brittle intermetallic Fe-Al compound (IMC) at the interface of the joint. The authors have been researching in order to minimize the thickness of this brittle IMC for getting the excellent joint strength and have found that the formation of this brittle IMC is regionally prevented by using the advanced hot-dip aluminized steel sheet and by adopting the suitable joining conditions.
In particular this paper focuses the mechanism of creating this IMC free region in case of MIG-braze welding and the results obtained are as follows.
(1) The creation of IMC-free region is initiated as the first process by the dissolution of the τ5 phase (Fe-Al-Si) in the aluminized layer into the weld metal, and the temperature more than 886K for dissolution during MIG-braze welding and the use of filler metal for dilution of Fe and Si in τ5 phase, have significant effects.
(2) As the second process, the diffusion between aluminum-alloy weld metal and base steel is restricted by AlN on the surface thin layer of the base steel existed under 908K temperature during MIG-braze welding.
