Analysis of intermetallic layer in dissimilar TIG welding-brazing butt joint of aluminium alloy to stainless steel

Intermetallic layer of dissimilar tungsten inert gas welding-brazing butt joint of aluminium alloy/stainless steel has been studied. A visible unequal thickness intermetallic layer has formed in welded seam/steel interface, and the thickness of the whole layer is <10 mu m. The interface with Al-12Si filler metal consists of iota(5)-Al8Fe2Si layer in welded seam side and theta-(Al,Si)(13)Fe-4 layer in steel side with the hardness values of 1025 and 835 HV respectively, while the interface with Al-6Cu filler metal consists of theta-Al-13(Fe,Cu)(4) layer with the hardness of 645 HV. The average tensile strength of the joint with Al-12Si filler metal is 100-120 MPa, and the fracture occurs at theta-(Al,Si)(13)Fe-4 layer, while the joint with Al-6% Cu filler metal presents high crack resistance with tensile strength of 155-175 MPa, which reaches more than 50% of aluminium base metal strength.