Microstructure and corrosion behaviour of A356 aluminium alloy modified with Nd

The microstructure of a gravity-cast A356 aluminium alloy modified with 0.4 wt% Nd and its corrosion behaviour in 3.5 wt% NaCl solution is investigated. The addition of Nd refines the eutectic silicon and results in the formation of Nd-containing intermetallics, which show smaller potential differences relative to the α-Al matrix than the Fe-rich intermetallics in the unmodified alloy. In 3.5 wt% NaCl solution, A356 and A356Nd alloys reveal localized corrosion attack at the Fe-rich/α-Al interfaces, which is then followed by localized corrosion through the eutectic areas. A more refined microstructure and the presence of Nd-rich phases in the A356Nd alloy considerably improves its pitting corrosion resistance compared with the A356 alloy which shows severe pitting corrosion.