Secondary-phase particle drag and pinning
Secondary-phase particles are frequently observed in different alloys: light elements, e.g. carbon, boron, nitrogen and oxygen within multicomponent alloys may convert to carbides, borides, nitrides and oxides respectively, which are mostly stable particles dispersed within the matrix. There also can be inclusions and intermetallic compounds as secondary-phases particles. Since the particles are generally small compared to the average grain size, they are able to interact with moving grain boundaries. Thus, they influence any corresponding property of material such as thermal stability and mechanical strength.
In this project, we are using multiphase-field method to characterize the drag and pinning effect under certain conditions.
Characterization of the interaction: It is shown that for an interface with constant driving force there would be severe drag effect before pinning which can be determining in the phenomena such as abnormal grain growth. The severe drag is a result of balance between deformed interface and the particle drag. The formation of a triple line between the particle and two grains applies a drag force against the migration of the interface (see figure above) We are doing large-scale simulations (many particles, many grains) for further investigations.
Single particle interaction.
Effect of particle’s shape: It is already known that ellipsoid or cubic particles can have different drag and pinning effect. The role of irregular secondary materials such as carbon nanotubes is under investigation.