Metallurgical and mechanical investigations of aluminium-steel butt joint made by tungsten inert gas welding–brazing

Abstract
Dissimilar metals of 5A06 aluminium alloy and SUS321 stainless steel were butt joined by tungsten inert gas welding–brazing with BJ380A filler metal and modified non-corrosive flux. The interface in seam/steel is made up of two kinds of intermetallic phase layers, τ 5-Al7Fe2Si phase in the seam side and θ-FeAl3 phase in the steel side. The granular phase in welded seam is CuAl2, and the lath shaped phase is τ 6-Al5FeSi. In the fusion area, the chainlike phase is Al–Si eutectic structure, and the block-like phase is Al6(Fe,Mn). The tensile strength of the butt joint reaches 125 MPa, and fracture occurs at τ 5-layer, with highest hardness value of 950 HV. The present joint without coated layer can reach the same level to those with coated layer.