Influence of aluminum casting alloys chemical composition on the interaction with a 304L stainless steel insert

The microstructure and mechanical properties of specimens made out of two different aluminum casting alloys, AlSi7Mg and AlSi9Cu, reinforced with a stainless-steel AISI 304 wire mesh and obtained by gravity casting were investigated. Specimens were observed by optical and scanning electron microscope in both as-cast and solution heat treated conditions with the aim to investigate the effect of matrix chemical compositions on the steel-matrix bonding. No intermetallic phases were observed at the interface in the as-cast conditions. However, a higher fraction of lack-of-filling defects as well as lack-of-bonding areas were detected in the AlSi7Mg alloy. The solution heat treatment induced the precipitation of different thick and brittle intermetallic layers, which compositions depend on aluminum alloy, in the areas where a metallurgical bonding formed during casting. Despite a little improvement of the elongation at fracture induced by silicon particle spheroidization caused by the heat treatment, the brittle fracture at the interface during tensile tests didn't allow the reinforcement to work in both the aluminum matrixes. Finally, basing on the obtained results, improvements are suggested that take into account both the preconditioning of the reinforcement surface and its geometry.