Corrosion behavior of Al-Si alloys as a function of cooling rate

Kurzfassung

Components in the automotive and aerospace industries made of aluminum alloys offer considerable potential for weight reduction and good recyclability, which additionally complies with circular economy principles. Accordingly, the development of both structural and functional aluminum components is a crucial part of lightweight design strategies for higher sustainability. The microstructure of metallic materials can vary considerably depending on part geometry and manufacturing process, due to variations in cooling rates during solidification by casting and even additive manufacturing processes. So far, the effects of cooling rate on the microstructure and corrosion behavior of Al‑Si alloys have been investigated only in limited and less systematic studies. To address this, a systematic investigation was conducted on an Al7Si0.6Mg alloy (F357), linking variations in corrosion mechanisms to the size and characteristics of cast microstructures in both as built and heat-treated conditions, including their nano-structural features. The cast microstructures with varying cooling rates were synthesized using levitation techniques, followed by an investigation using scanning and transmission microscopy methods as well as the associated hardness property testing. Subsequently, potentiodynamic and static corrosion tests were performed in sodium chloride solutions with various concentrations. The results show that corrosion behavior is strongly influenced by the microstructure determined by cooling rate, highlighting the challenges that production induced microstructural variations pose for alloy performance.