Influence of TiC particles on grain boundary structure and solute atomic diffusion in TiC/Al-Cu composites

The addition of intermetallic TiC particles can greatly improve the mechanical properties of materials. However, the impact of TiC particles on grain boundary transformations and solute atom diffusion behavior at grain boundaries is not fully understood. Here, we attempt to clarify this using TiC/Al-Cu composites as an example. Electron backscatter diffraction (EBSD) analysis revealed that TiC particles hinder the transformation of coincidence site lattice (CSL) grain boundaries from Σ3 to Σ5, thereby maintaining a high proportion of Σ3 grain boundaries in TiC/Al-Cu composites. First-principles calculations reveal that Σ3 grain boundaries, compared with Σ5, lower the diffusion activation energy by reducing the vacancy formation energy and diffusion energy barriers, facilitating rapid diffusion of Cu atoms along the grain boundaries. Further analysis of the electronic structure indicated that the strengthening of the covalent bonding characteristics and enhanced stability of the chemical bonds between atoms impeded the migration of solute atoms. This study offers valuable theoretical insights into the connection between interface characteristics and atomic diffusion behavior.