Characteristics of Liquid Metal Crystallization
Metals are generally in solid form in nature, but when heated to an appropriate temperature, they will enter the liquid phase, and the properties of metals will change. Liquid metal crystallization is a thermodynamic phase change from liquid to solid. Liquid metal crystallization mainly includes the processes of nucleation, growth, impurity segregation and phase selection. There are many variable factors in these processes. And depending on the details of the process and the crystal structure of the material, different crystallization characteristics will show in different circumstances. This article will mainly discuss the characteristics of liquid metal crystallization.
The nucleation process of liquid metal crystallization is a very important stage in the crystallization process. Nucleation accelerates the cooling of the metal melt, and its time scale is related to the type and size of the crystal nucleus formed. If the nucleation rate is too slow, the metal will have time to continue to cool, resulting in larger or more crystals. The nucleation process is affected by many factors such as temperature, material composition, and crystallinity. The results of the research show that the crystal nuclei grow faster in smaller sizes.
The growth of grains during liquid metal crystallization is usually dominated by the diffusion of atoms and impurities to the grain boundaries. At this stage, the grain boundaries can move due to the difference in the impurity concentration gradient and the crystallization rate. And the diffusion process also helps to evacuate the impurities in the grain boundary, leading to homogenization grain.
During the crystallization process of liquid metal, impurity segregation also affects the microstructure and size of grains. There are two distinct types of impurity segregation: interfacial and bulk segregation. Interfacial segregation happens at the grain boundary and it is affected by the difference in impurity concentrations. In the bulk segregation, impurities will be segregated to the interior of the grain, where the impurity concentration is higher than its original concentration. Impurity segregation can change the structure of the material, as well as influence the strength and other properties of the material.
The last stage of liquid metal crystallization is the selection of crystal phases. During this stage, any unwanted phases will be eliminated and only one crystalline phase will remain. This is determined by the parameters of the crystallization process such as temperature, cooling rate, and concentration. Several mechanisms can be used in this process, such as solidification, recrystallization and surface segregation.
To sum up, liquid metal crystallization displays different characteristics in different circumstances. The characteristics of liquid metal crystallization include nucleation, grain growth, impurity segregation and crystal phase selection. All of these processes are affected by many variables and the details of the processes can lead to different crystallization characteristics of the material.
