Macrosegregation in Al–Si welds made with dissimilar filler metals

Abstract

The microstructure and compositions of Al–Si welds made by gas metal arc welding with filler metals which are different, i.e. dissimilar, from the workpiece in composition were examined. The liquidus temperature of the weld metal (TLW) was either below or above that of the base metal (TLB). TLW<TLB was achieved by welding 1100 Al (commercially pure Al) with filler metal 4047 (essentially Al–12Si). Base metal-like beaches, peninsulas, and islands were found along the fusion boundary, and the beaches were discontinuous. These results suggested the macrosegregation mechanism was Mechanism 1 proposed recently by the authors. Contrarily, TLW>TLB was achieved by welding alloys at or close to the Al–12·6Si eutectic composition with filler metal 1100 Al. A filler rich zone near the weld bottom and a base metal-like beach continuous along the fusion boundary were found. These results suggested the macrosegregation mechanism was Mechanism 4 proposed recently by the authors.