Abstract:

Taking the AZ series magnesium alloy containing rare earth as the base alloy, specimens with 5%, 7% and 9% Al were prepared, and solution treatment at 435 ℃ for 24 h+aging at 200 ℃ for 24 h was carried out. Then the microstructures of as-cast, solid solution treated and aged specimens were observed, the mechanical properties and corrosion resistance of the specimens after aging were measured. The results show that the as-cast microstructure of the specimens is mainly α-Mg+β-Mg₁₇Al₁₂+Al₁₁ (La,Ce)₃ and (La,Ce)Al₄. With the increase of Al content, the β-Mg₁₇Al₁₂ phase and rare earth compounds increase, and the grain refinement is achieved. After solution treatment, the β-Mg₁₇Al₁₂ phase in the microstructure gradually dissolves, the dissolution becomes uncompleted with the increase of Al content, and the undissolved strengthening phase β-Mg₁₇Al₁₂ and the rare earth compound phase disperse in and near the grain boundary. After aging treatment and with the increase of Al content, β-Mg₁₇Al₁₂ phase continues to precipitate and increases in the microstructure, and the size of rare earth compound phase is refined. With the increase of Al element, the tensile strength and hardness of the specimen increase gradually, while the plasticity and toughness are getting worse, the corrosion resistance is becoming better.

Key words: AZ series magnesium alloy, aluminum content, microstructure, mechanical properties, corrosion resistance