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A team of Chinese and American scientists has revealed the internal mechanism of high strength and high plasticity of metal materials. This discovery will provide support for the optimized design of key materials and the development of high-performance alloys. Related results were published online in the "Nature" magazine on the 10th Beijing time.
In recent years, scientists have discovered that by dissolving a variety of elements and other atoms together in theory, high-entropy alloys with ordered atoms and disordered elements can be produced in theory. Some high-entropy alloys can have both high strength and high plasticity. Therefore, the dilemma of "fish and bear paw" in traditional metals is difficult to achieve.
Professor Yu Qian from the team of academicians Zhang Ze of the School of Materials Science and Engineering, State Key Laboratory of Silicon Materials and Electron Microscopy Center of Zhejiang University, Professor Zhu Ting of the Department of Materials, Georgia Institute of Technology, and Professor Robert Rich of the Department of Materials, University of California Berkeley From the decryption of the element distribution in the high-entropy alloy, the mystery of "Bai Lian Gang" turned into "Wrap Fingers" was revealed.
The high-entropy alloy is composed of a variety of elements dissolved in high concentration, with clear crystal structure and chaotic atom distribution. The researchers found that the elements in the high-entropy alloy showed unique concentration wave fluctuations through atomic-scale element distribution. The concentration of various elements fluctuated between 25% and 15% between the lattices.
The local irregular arrangement of atoms is called a dislocation, and its presence has a great influence on the physical properties of the material, especially the mechanical properties. Under the high-magnification electron microscope, the researchers saw that the dislocation lines in the high-entropy alloy, like the waves of Qiantang tide, rolled forward and formed a "cross tide" or even "return tide."
"This dislocation movement leads to increased interaction between dislocations, providing more possibilities for deformation, making the alloy have better uniform deformation ability and better strength." Yu Qian said.
The researchers introduced that the unique concentration wave control in the high-entropy alloy is extremely fine and continuous, and is a controllable and efficient method of material toughening. The characteristics of high entropy alloy having both strength and plasticity and excellent low temperature performance are promising in the preparation of materials in areas with severe temperature requirements, such as aviation, and will also have important applications in the field of collision avoidance.
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