Microstructural evaluation in dissimilar liquid phase bonding of cast Al–Si alloy and stainless steel using pure zinc filler metal

Abstract

The metallurgical joining between cast A359 aluminium alloy and AISI321 stainless steel using pure Zn as the interlayer was performed slightly above Al–Zn eutectic temperature. The liquid phase was formed by a eutectic reaction between Al and Zn and subsequently isothermally solidified by diffusion of Zn into the A359 base metal (i.e. reactive transient liquid phase bonding). The formation of a Zn-rich diffusion affected zone in A359, incorporation of Si particles into the bond zone, formation of a thin Al–Fe–Si intermetallic at the steel interface, and isothermal solidification of the liquid phase and subsequent Al–Zn eutectoid transformation govern the microstructure of the joint. The resultant bond microstructure does not deleteriously affect the heat sink function of Al base metal.