Towards magnesium alloys for high-volume automotive applications

Recent developments in high-strength Mg-RE-based alloys: Focusing on Mg-Gd and Mg-Y systems

Texture evolution during static recrystallization of cold-rolled magnesium alloys

Although magnesium alloys, as the lightest structural alloys, offer significant potential for automotive applications, their applications remain limited due to their poor formability at room temperature. Since the strategies used for improving formability usually result in a degradation of strength, there are no high strength magnesium alloys showing good formability. Here we report an alloy design concept that can simultaneously provide high strength and good formability. Such designed alloy when subjected to an appropriate processing technique shows a combination of strength and formability that surpasses those of the existing magnesium alloys reported so far. The alloy design concept used in the present study is based on the utilization of alloying elements that can induce precipitation, as well as maximize the segregation of other texture-controlling alloying elements. Such developed alloy is expected to broaden the application of Mg alloy sheets, which are now starting to gain acceptance by automotive industries.

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Designing a magnesium alloy with high strength and high formability.

Current issues in magnesium sheet alloys: Where do we go from here?

Ca was added to Mg-1Zn and Mg-6Zn alloys to modify their texture, and the origin of texture modification by Ca addition has been investigated. It shows that Mg-1Zn-1Ca (ZX11) and Mg-6Zn-1Ca (ZX61) alloy sheets in the as-rolled condition show the textures having a splitting of basal poles toward the rolling direction and a splitting of basal poles toward the transverse direction, respectively. An analysis of the microstructure in the as-rolled condition shows that two different types of twins become active during rolling, double twins for ZX11 and tension twins for ZX61, suggesting that double twinning and tension twinning promote a splitting of basal poles toward the rolling direction (ZX11) and transverse direction (ZX61), respectively. On the other hand, after annealing, both alloy sheets show a weakened texture characterized by a splitting of basal poles toward the transverse direction. During annealing, the growth of tension twin-oriented grains occurs, resulting in the texture having a splitting of basal poles toward the transverse direction in both alloys. These alloys show not only higher yield strength but also better stretch formability than Al 5052 alloy, showing their potential as highly formable Mg sheet alloys.

Texture Evolution in Mg-Zn-Ca Alloy Sheets

Effect of Sn addition on the microstructure and deformation behavior of Mg-3Al alloy

Microstructure and texture evolution of Mg alloys during twin-roll casting and subsequent hot rolling

Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability.

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Myeong-Shik Shim

Papers

Current issues in magnesium sheet alloys: Where do we go from here?

Texture Evolution in Mg-Zn-Ca Alloy Sheets

Effect of Sn addition on the microstructure and deformation behavior of Mg-3Al alloy

Microstructure and texture evolution of Mg alloys during twin-roll casting and subsequent hot rolling

Twinning-mediated formability in Mg alloys