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.