Microstructure Evolution of B₄C/Al Interface: A First-Principle Study

The microstructure evolution of the B₄C/Al interface is very complicated, which has not been fully understood yet. The main products reported in the literature works are Al-B phases (AlB₂ and AlB₁₂) or Al-B-C phases (Al₃BC and AlB₁₂C₂). However, the most common Al₄C₃ phase in Al-C systems was rarely reported, which could not be explained by reaction thermodynamics. In the present work, the interfacial bonding evolution between B₄C and Al was calculated by the thermodynamic analysis and first-principle method. According to the thermodynamic analysis, Al-B phases (AlB₂ or AlB₁₂) and Al-C phase (Al₄C₃) would be formed simultaneously, which was inconsistent with the experimental result. Furthermore, the first-principle calculation indicated the formation of strong chemical bond at the B₄C/Al interface. The population bonding analysis revealed that the interface bonding was B-Al bond. Due to the pull of chemical bond forces, the B elements tended to be enriched at the interface, while the C element tended to be far away from the interface. Eventually, the interface-enriched B element preferentially reacted with the Al matrix to form AlB₂ and AlB₁₂ and further evolved to be Al-B-C phases (Al₃BC and AlB₁₂C₂). However, the C element could not preferentially participate in the reaction.