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Atomic diffusion is a common phenomenon in nature and a fundamental process in the preparation and processing of materials to regulate their structural properties. The high atomic diffusion rate of metals can be used to substantially modulate the structure and properties of metallic materials at lower temperatures to obtain good overall properties. However, high diffusion rates can destabilize the structure of metallic materials at high temperatures, resulting in the loss of many properties. How to effectively reduce the atomic diffusion in metals and alloys and improve the stability of material structure and properties at high temperatures is one of the important bottlenecks restricting the development of metallic materials.
Recently, the National Key R&D Program "Nano Science and Technology", entrusted by the High Technology Research and Development Center of the Ministry of Science and Technology, has made important progress in the project of "Research on the construction and service behavior of new nano-metal materials". The research team from the Institute of Metals, Chinese Academy of Sciences (IOM) has discovered that the restricted crystal structure can effectively inhibit atomic diffusion in supersaturated Al-Mg alloys with very fine grains at high temperatures. By forming a stable structure of restricted crystals, the intermetallic phase precipitation process of nanograins controlled by atomic diffusion and the growth coarsening behavior of grains are effectively suppressed to the equilibrium melting temperature range as the annealing temperature of the sample increases. Around this temperature, the apparent cross-border diffusion rate is reduced by about 7 orders of magnitude compared to that of the Al-Mg alloy sample without restricted crystal structure. The confined crystals provide a strong barrier to stop the diffusion of atoms in the metal and alternative alloys, achieving much higher stability than conventional alloys at the melting temperature.
The research results promise engineered alloys developed using confined crystal structures and open up a whole new pathway for the development of, highly thermally stable metallic materials. The related research results were published in Science in August 2021.
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