This high diffusivity makes the metal structure adjustable on different length scales, but it also brings instability of structure and customized performance. This instability is the main bottleneck in the development of metal materials, which greatly limits their technical application at high temperature.
On Aug. 6, local time, the top academic journal Science (Science) published a research report (Report) entitled "Suppressing atomic diffusion with the Schwarz crystal structure in supersaturated Al-Mg alloys" by the Institute of Metals of the Chinese Academy of Sciences, which provides a new way to solve the instability caused by high atomic diffusivity in metals at high temperatures.
The correspondent authors of the study are Academician Lu Ke, doctoral supervisor of the Institute of Metals, Chinese Academy of Sciences, and researcher Li Xiuyan.
Luke has devoted himself to the research of metal nanomaterials for more than 20 years, published more than 400 papers in academic journals, and obtained more than 40 invention patents. He has won the Acta Materialia Gold Medal, the Humboldt Research Award in Germany, the Outstanding Young Scholars Award of the first Hong Kong Qiushi Foundation, the ISMANAM Gold Medal of the International Metastable and Nanomaterials Annual Conference, the Chinese Young Scientist Award, the Ho Liang Ho Foundation Science and Technology Progress Award, and the TWNSO Technology Award of the third World Academy of Sciences. In 2020, Luke won the Future Science Award "material Science Award" for his groundbreaking discovery and use of nano-twin structure and gradient nanostructure to achieve high strength, high toughness and high conductivity of copper metal.
Since October 2018, Lu Ke has been the vice governor of the people's Government of Liaoning Province, responsible for science and technology, sports and other fields. In charge of Liaoning Provincial Department of Science and Technology (Bureau of Foreign experts), Sports Bureau, important technological innovation and R & D base construction engineering center (Industrial Technology Research Institute).
It is written that because of the nature of interatomic bonds, the atomic diffusivity in metals is significantly higher than that of ceramics and compounds with covalent or ionic bonds. In the process of synthesis and subsequent treatment, by adjusting the diffusion control process, the structure is highly adjustable on different length scales, so that the metal materials have a wide range of properties. For example, aluminum alloy hardens by precipitation of intermetallic compounds near room temperature. In thermomechanical treatment, the strength and plasticity of steel can be widely adjusted by controlling diffusion phase transformation.
However, when the metal is exposed to high temperature or mechanical load, the high atomic diffusivity makes the structure and customized performance of the metal unstable. This instability is the main bottleneck in the development of metal materials, which greatly limits their technical application at high temperature.
Suppressing the diffusion of atoms in metals is a challenge, especially at high temperatures, the team said. The interface or grain boundary (GBs) associated with a more open structure is considered to be a fast diffusion channel of atoms relative to the lattice. The diffusion along the GB can be slowed down by optimizing the GB segregation of other elements. However, with the increase of the degree of alloying, the formation of the second phase increases, and the interfacial alloying is also limited.