职位/职称: 教 授
报告题目： Composition formulas of alloys based on cluster-plus-glue-atom model
Industrial alloys all have specific chemical compositions. They are all based on solid solutions characterized by chemical short-range ordering. However, the lack of an accurate structural tool to address the characteristic short-range-order structures constitutes the major obstacle to composition design. Since alloys with good comprehensive performance do have specific chemical compositions, their compositions should correspond to molecule-like specific structural units. After a long effort of more than a decade, we have developed a new structural tool, so-called the cluster-plus-glue-atom model, to describe any short-range-ordered structures. In particular, solid solutions can be understood as being constructed from the packing of special chemical units covering only the nearest-neighbor cluster and a few glue atoms located at the next outer shell, expressed in molecule-like cluster formula [cluster](glue atoms). Such units are representative of the whole structures, just like molecules do for chemical substances. After introducing Friedel oscillation, the cluster-plus-glue-atom model is turned into the cluster-resonance model that provides also the inter-cluster packing modes. Ideal atomic density is hence obtained which is only proportional to the number of atoms in the unit and the cube of the cluster radius. The calculation of chemical unit is then possible and is conducted in typical binary Cu-based industrial alloys. The calculated formulas give chemical composition that highly agree with the most popular alloy specifications, as exemplified by [Zn-Cu12]Zn4 that interprets the most widely used a-brass Cu-30Zn. This approach is also extended to high entropy alloys, which is regarded as multi-solvent solid solutions. Our work reveals the composition origin of industrial alloys and demonstrates its high potential for developing chemically complex alloys.