Effects of rare earth element content on the microstructural properties and corrosion resistance of Al-Zn alloy

Abstract

In this paper, Al-Zn alloys with different Ce- and La contents (<1 %) were prepared by semi-continuous casting method, and the cost of adding a large amount of RE elements to large ingots was considered. The effects of rare earth element Ce and La content on the microstructure, properties and corrosion behavior of Al-Zn alloy were systematically studied. The results showed that the addition of RE promoted the formation of the Al₁₁Ce₃ phase, but the addition of too high a high amount led to the formation of the deleterious crude primary Al₁₁Ce₃ phase. With the increase of rare earth elements, the hardness of Al-Zn alloy gradually increases ( Approximately 22 % increase ), the wear resistance is improved ( Friction rate decreased from 54.3 to 36.5 mgN⁻¹m⁻¹ ), and the corrosion resistance is also improved. This can be attributed to the strengthening of the matrix by Al₁₁Ce₃ and the formation of a dense protective film, resulting in improved corrosion performance. Corrosion of alloys is caused by pitting corrosion. Corrosion starts from the passivation state and reaches a pitting stability phase through the pitting induction period.