Effects of Al and Zn contents and heat treatment on microstructures and tensile properties of Mg-AI-Zn alloys

• Published in: Keikinzoku Vol. 55; no. 10; pp. 456 - 462
• Main Authors: Yoshida, Yu, Arai, Keita, Itoh, Shota, Kamado, Shigeharu, Wada, Toshiaki, Matsunaga, Takashi, Yoshimoto, Takashi, Kojima, Yo
• Format: Journal Article
• Language: Japanese
• Published: 01.10.2005
• ISSN: 0451-5994

The effect of Al and Zn contents and annealing conditions on the microstructural evolution and tensile properties were investigated by using Mg-Al-Zn alloys containing 2.0 ~ 4.5 mass% Al and 0.7 ~ 1.5 mass% Zn. The number of shear bands developed during hot rolling increases with increasing Al and Zn contents. As a result, grain refinement in the as-rolled (F) specimens containing large amount of Al and Zn leads to high strength and high ductility at room temperature. At 498 K, the tensile strength of the investigated alloys is almost the same, while the elongation of the F-specimens increases with increasing Al and Zn contents, leading to 150% in Mg-4.5%A1-1.5%Zn alloy. High Al and Zn contents alloys significantly accumulate large working strain in grain interiors, and involve large amounts of high angle grain boundaries and precipitates, which can become the nucleation sites for recrystallization. Therefore, dynamic recrystallization in such alloys occurs at small strain region during tensile test. This dynamic recrystallization causes reduction of flow stress and large elongation by grain boundary sliding at high temperatures. The tensile tests at 498 K reveals that the F-specimens containing large residual working strain exhibits lower flow stress and larger elongation to failure than the specimens annealed at 623 K for 1 h as a result of occurrence of dynamic recrystallization at small strain region.