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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°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.

The present study focused on reinforcing Al–Si–Cu alloy with a cast iron insert and using Zn– xAl–3Si–0·5Mg (wt-) intermediate alloys by the cast joining technique to take advantage of lightness and stiffness of the hybrid structure. The experimental set-up consisted of coating the insert using hot dipping method followed by immersing the coated insert into the Al melt and allowing the system to cool down to the room temperature. The quality of Al–Fe joints in terms of morphology, thickness, chemistry and microhardness was evaluated as a function of coating composition and immersion time in the Al melt. Characteristics of reaction layer at the coating/insert interface and its effects on the joint properties were determined using microstructural analysis and thermodynamic calculations. Combination of a suitable coating containing 27 wt-Al and optimised process parameters, including 1 min immersion time, resulted in the formation of an Al–Fe joint with promising characteristics.

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