Effect of T4 and T6 treatment on corrosion of die cast AZ91D magnesium alloys in 3.5% NaCl
(1.辽宁省沈阳市科学院金属研究所
2.北京市北京化工大学材料科学与工程学院
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China)
2.北京市北京化工大学材料科学与工程学院
3.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China)
Abstract: The effect of heat treatment on microstructure and corrosion behavior of die-cast AZ91D magnesium alloys in 3.5% NaCl solution was investigated by SEM, EDX, XRD and electrochemical technique. It is found that the distribution of β phase influences the corrosion morphology. Corrosion occurs preferentially in primary α phase and presents pitting corrosion feature in die-cast AZ91D. After homogenization of T4 treatment, β phase dissolves in α phase and forms a single phase with α matrix, and the corrosion form turns to localized corrosion. The attack initiates at local site, expands towards deep direction and produces “digging effect”. After artificial aging of T6 treatment, β phase is produced in abundance and provides a great deal of effective micro-cathode for anodic dissolution, and the corrosion form exhibits in general corrosion.
Key words: AZ91D magnesium alloys; microstructure; corrosion behavior