Recently, NEU, together with Shanghai Jiao Tong University, Max Planck Institute for Sustainable Materials (formerly Iron and Steel Institute), the University of Utah, Chongqing University and East China University of Science and Technology and other scientific research institutions, published important research achievements in the field of light aluminum alloy materials with high iron (Fe) content, titled with “Deformation faulting in ultrafine-grained aluminum alloys-Nucleation mechanisms and critical assessment of strengthening-ductilization contributions” and “Tuning generalized planar fault energies to enable deformation twinning in nanocrystalline aluminum alloys” on Acta Materialia and International Journal of Plasticity.
With the increasing attention to circular economy in the world, how to separate economic and population growth from resource consumption and production of metal raw materials has become an important problem to be solved urgently. The feasible way to solve this major challenge is to realize the sustainable regeneration of metal structural materials. As the most widely used non-ferrous metal, the production process of aluminum is a process with high energy consumption (the energy required is more than ten times that of steel production) and high emission (the greenhouse gas emission accounts for 3% of total greenhouse gas emissions in industrial production), which brings great pressure on the energy-saving and environmental protection policies implemented by China. As a sustainable recycling material, compared with the production of primary aluminum, remelting 1 kg of aluminum waste can save up to 90% of energy and reduce up to 95% of greenhouse gas emissions. Therefore, the sustainable recycling of aluminum is a key component of the global circular economy strategy.
However, in order to realize the high-quality utilization of recycled aluminum (especially wrought aluminum alloys) based on the remelting path, the solution of the consensus is to greatly increase the tolerance value of impurity Fe in wrought aluminum alloys. This undoubtedly requires researchers to deepen their understanding of the accumulation and occurrence state of Fe in alloys.
In this research, taking the deformed aluminum alloys with high magnesium (Mg) content as the model materials, the evolution behavior of Fe under different processing paths was systematically and deeply explored by artificially adding Fe with weight ratio of 1%, combined with large plastic deformation and thermo-mechanical processing technology. Through the fusion of multi-scale characterization technology, it was found that mechanical alloying drove excessive Fe element to dissolve in Al lattice, forming supersaturated solid solution alloy, while driving grain boundaries to emit imperfect dislocations, thus forming a large number of stacking faults and a small number of twin crystals. In the subsequent hot extrusion consolidation process, excessive Fe was desolventized and reacted with Al, finally uniformly dispersed in the alloy matrix in the form of micrometer, ultrafine-grained intermetallic compound particles. Unfortunately, based on the observation of microstructure of deformation and the evaluation of strengthening of stacking faults, it was further found that stacking faults had limited contribution to the severe plasticity of materials. Therefore, it needs to be further optimized.
The first author of these two papers is Zhang Jingfan, a doctoral student, and their co-authors are Assistant Professor Yang Chao of Shanghai Jiao TongUniversity, Doctor Li Yue of Max Planck Institute for Sustainable Materials, Professor Pan Hucheng of NEU and Associate Professor Zhou Dengshan of NEU. The research is supported by the National Natural Science Foundation of China and the "Prospering Mongolia through Science and Technology", Action Program Special Project of Shanghai Jiao Tong University.
