New Progress Has Been Made In The Research of New Multi-level Nanostructured Magnesium Alloys

- 2022-01-20-

Magnesium alloys are widely used in aerospace, automobile industry, pharmaceutical and chemical industries due to their high specific strength and low density. 

However, due to its inherent close-packed hexagonal structure, its ductility is poor, and obtaining magnesium alloys with both high strength and high plasticity has also become an important direction of current research. 

Preliminary research results show that the introduction of gradient nanostructures on the surface of magnesium alloys through surface mechanical grinding treatment (SMAT) can significantly improve the microhardness and wear resistance of magnesium alloys, but lead to a significant reduction in its plasticity.

Figure 1. Structure and composition of Mg-Zn-Ca dual phase metallic glass (NDP-MG)

Academician Lv Jian of the Greater Bay Area Research Department of the Shenyang National Research Center for Materials Science, Institute of Metals, and his collaborators have previously found that the super-nano dual-phase magnesium alloys with amorphous encapsulated nanocrystals can achieve near-theoretical strength (Nature 545, 80-83 (2017 )), taking AZ31 alloy as the research object, firstly using SMAT to obtain gradient nanocrystals on the surface of magnesium alloy, and then depositing Mg-based dual-phase metallic glass film (Mg-Zn-Ca) on the surface of the alloy by magnetron sputtering, Innovatively combining nano-dual-phase metallic glass with gradient nano-crystalline structure, a new multi-level structure magnesium alloy is designed.

Figure 2. Structure and mechanical properties of nano-gradient SMAT magnesium alloy

The research results show that the yield strength of the alloy is 31% higher than that of the original alloy, reaching 230MPa, which is comparable to the strength of SMAT magnesium alloy. ) level, thereby achieving an effective combination of high strength and high plasticity. 

Further research found that the excellent mechanical properties of multi-level nanostructured magnesium alloys include three deformation mechanisms, including: multiple shear bands and nanocrystallization of dual-phase metallic glasses, metallic glasses to block crack extension of nanocrystalline layers, and SMAT nanocrystalline The grains of the layer grow. Similar new nanostructures can yield high-strength and high-plastic copper. 

Figure 3. Room temperature mechanical properties of dual-phase metallic glass + SMAT (NDP-MG coated SMAT-H′) magnesium alloy

This alloy structure design concept is expected to realize the combination of high strength and high elongation in other alloy systems, especially the close-packed hexagonal structure alloy, and guide the design of new materials in the future.

Fig. 4. SEM morphologies of NDP-MG before deformation and after 6% stretching

The related results were published in Advanced Science under the title "Nano-dual-phase metallic glass film enhances strength and ductility of a gradient nanograined Magnesium alloy".
Paper link

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