Interaction of 308 stainless steel insert with A319 aluminium casting alloy

In the metallurgical connection of aluminium alloys to steels, it is important to restrain the formation and growth of hard and brittle intermetallic phases at the aluminium/steel interface to enhance the mechanical behaviour of the joint. The influence of two coating materials, electroless plated copper (for 20 and 40 min) and galvanised zinc (at 480 and 550 degrees C), on the quality of the interface between 308 stainless steel and A319 aluminium matrix was investigated. Copper led to the formation of a compact, solid inhibition layer against the elemental diffusion at the aluminium-steel contact temperature, while zinc resulted in the formation of a composite intermetallic layer which was open in structure. Comparing all interfaces formed between the insert and Al matrix, the 40 min Cu coated steel revealed the lowest values in terms of the thickness and microhardness after immersion into the molten aluminium.