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The research team led by Lu Lei, a researcher at the National Institute of Materials Science (China) of the Institute of Metal Research, Chinese Academy of Sciences, collaborated with Dr. Lu Ke, Ph.D., Dr. Huang Xiaoxu from the Risf National Laboratory in Denmark, and obtained a unique stable interface structure using the coherent twin crystal boundary. Ultra-fine feature size nanostructured metals, and found that reducing the thickness of the tantalum wafer layer will increase the strength of the material. This finding indicates that when the characteristic size of a pure metal is reduced to the order of nanometers, the change of the plastic deformation mechanism leads to the occurrence of extreme strength, and at the same time exhibits an ultra-high work hardening effect which is not possessed by general metallic materials.
Lu Lei and his collaborators used pulse deposition techniques to explore the average thickness of tantalum wafer layers in pure copper samples to a thickness of about 4 nm through a detailed process and found that the strength of the material reducing the thickness of the tantalum wafer layer was increased. When the thickness of the germanium wafer layer is 15 nm, the material strength reaches a maximum. Further reducing the thickness of the germanium wafer layer, the intensity is reduced and the softening phenomenon occurs. As the wafer layer is reduced, the plasticity and work hardening ability of the sample monotonously increases. When the germanium wafer layer is less than 10 nm, the work hardening coefficient exceeds the work hardening coefficient of the coarse crystal pure copper.
In the process of plastic deformation, the coherent twin boundaries can effectively block dislocations and have similar strengthening effects as ordinary grain boundaries. At the same time, the coherent twin boundary can absorb a large number of dislocations as a dislocation slip surface, and the twin boundary structure is more stable than the ordinary grain boundary, and its excess energy is only 1/10 of the ordinary grain boundary. Therefore, the nano twin structure is much more stable in energy than the nanocrystal structure of the same chemical composition. The acquisition of this stable ultrafine nano twin structure is not only a breakthrough in the traditional material preparation technology, but also an in-depth study of the mechanics of metal materials. The nanoscale effect of behavior provides the possibility.
Chinese scholars obtain ultra-fine features of nanostructured metals
Recently, the US Science magazine reported new discoveries made by Chinese scholars in the field of metal materials research. The reviewers believe that the authors have made significant discoveries in the use of nanocrystalline materials to enhance the nature of materials, not only enriching and broadening the understanding of the nature of nanoscale material plastic deformation, but also to further develop high performance nanostructured materials and The application provides important clues.