Professor Zeng Xiaoqin's team of Shanghai Jiaotong University published the research results of high-strength stainless magnesium alloy in Nature communications

On October 3, 2022, the internationally renowned academic journal Nature Communications published the research results of Professor Zeng Xiaoqin's team at the Institute of Materials Intelligent Design and Processing, Institute of Materials Science and Engineering, School of Materials Science and Engineering, Shanghai Jiao Tong University, "Towards development of a high-strength stainless Mg alloy with Al-assisted growth of.
" passive film”
。 Through the alloying design, a protective film layer with long-lasting passivation effect is introduced on the surface of magnesium alloy, and a preparation scheme for greatly improving the strength and corrosion resistance of magnesium alloy is proposed, which subverts the traditional understanding that
magnesium alloy alloying will greatly lose corrosion resistance due to galactic corrosion while improving the strength.
The research paper is first published by Shanghai Jiao Tong University, with Dr.
Qingchun Zhu of School of Materials Science and Engineering of Shanghai Jiao Tong University as the first author, and Dr.
Yangxin Li and Professor Xiaoqin Zeng as co-corresponding authors
.

Nature Communications publishes research online

In the context of global efforts to achieve the "double carbon" goals of "carbon peaking" and "carbon neutrality", magnesium alloys, as the lowest density metal structural materials, have natural advantages
in areas where lightweight needs are urgently needed such as transportation and aerospace.
For a long time, low absolute strength and insufficient corrosion resistance have been the two major bottlenecks hindering the large-scale application of magnesium alloys
.
Alloying (especially the addition of rare earth elements) is one of the effective means to greatly improve the strength of magnesium alloys, but most of the alloying of high-strength magnesium alloys in the second phase and matrix formation of primary batteries and cause fierce galvanic corrosion, thereby greatly reducing the corrosion performance
of magnesium alloys.
How to synergistically improve the strength and corrosion resistance of magnesium alloy through alloying design is one of
the hot spots and difficulties that academia and industry have long been concerned about.

In view of the above problems, Professor Zeng Xiaoqin's team from the School of Materials Science and Materials Science of Shanghai Jiao Tong University selected a typical high-strength Mg-Y alloy as the research object, and selected Al element for microalloying modification based on two assumptions: (1) The addition of Al element can form in situ autogenous Al2Y particle refinement grain and long-period stacking ordered structure (LPSO) strengthened phase in Mg-Y alloy, which can significantly improve the strength of casting and deforming Mg-Y-Al alloy and maintain good plasticity; (2) The dissolved Al element has a faster deposition rate than Zn and other elements on the surface of the magnesium alloy, which is conducive to promoting the surface film formation of magnesium alloy in the corrosive environment, and the high-strength stainless magnesium alloy with yield strength of 350 MPa, elongation rate of 8% and corrosion rate of less than 0.
2 mm y-1 (loss-in) is prepared by traditional gravity casting and extrusion deformation, and these performance combinations are better than the currently reported magnesium alloy (as shown in Figure 1f).

。 It is worth mentioning that the addition of a small amount of Al element promotes the rapid dense deposition of Y element in the alloy on the alloy surface, forming a passivation film with long-lasting protection (Figure 2-Figure 5), which effectively hinders the galvanic corrosion between the second phase and the matrix in the alloy, greatly reduces the microstructure sensitivity of Mg-Y-Al alloy corrosion (Figure 1) and the sensitivity of impurity elements (alloy iron content ~ 200 ppm), and provides a new design idea for the future application of casting and deformation of high-strength stainless magnesium alloy in industrial preparation
。 The research results have been applied for Chinese invention patents (authorized patent number: ZL202010198047.
9) and PCT US patents (published patent number: PCT/CN2021/080828).

Fig.
1 Comparison of the mechanical properties and corrosion resistance of Mg-11Y-1Al(WA111) alloy with other magnesium alloys in the literature

Fig.
2 Topography and elemental distribution of corrosion product films of Mg-11Y(W11) and Mg-11Y-1Al(WA111) alloys

Figure 3 Elemental composition analysis of corrosion product film on the surface of Mg-11Y-1Al alloy

Fig.
4 Comparison of electrochemical behavior of Mg-11Y and Mg-11Y-1Al alloys

Fig.
5 Schematic diagram of corrosion resistance mechanism of Mg-11Y and Mg-11Y-1Al alloys

Academician Ding Wenjiang put forward the idea of developing stainless magnesium usable for the project in 2012, and continued to care, participate in and promote the completion of this research
.
Special thanks to Dr.
Fuyong Cao of Xiamen University and Dr.
Dong Qiu of RMIT University of Australia for their suggestions
on this research work.
This research has been supported
by the National Natural Science Foundation of China (51825101, 51701121, 52001199) and the Shanghai Municipal Science and Technology Talents Sailing Program (17YF1408800).