Investigating coherent and semi-coherent interfacial structures and energetics in Al/Al3BC interfaces: Theoretical insights into aluminum matrix composites bonding

Understanding the intricate interfacial structures and energetics between ceramics and aluminum is crucial for elucidating the mechanical properties of aluminum matrix composites (AMCs). However, previous theoretical simulations primarily focused on coherent interfaces, neglecting lattice constant variations on heterogeneous interfaces, which has led to discrepancies with experimentally observed semi-coherent interfaces. Here, using recently synthesized Al/Al3BC AMCs as a case study to systematically construct six semi-coherent interfacial models containing 383 to 588 atoms. These models are used to investigate the Al(111)/Al3BC(0001) and Al(311)/Al3BC(0001) structures and their associated energetics. Additionally, we examine 39 coherent interfaces for comparison. Work of adhesion and interfacial energy results reveal that the stable termination for semi-coherent interfaces is Al(B), which contrasts with AlC termination observed in coherent interfaces. Both Al(111)/Al3BC(0001) and Al(311)/Al3BC(0001) semi-coherent interfaces demonstrate higher stability but lower bonding strength compared to coherent interfaces. Bonding strength and stability of Al(B)-terminated semi- coherent interface in Al(311)/Al3BC(0001) are lower than those in Al(111)/Al3BC(0001). Electronic structure analysis indicates that AlC-terminated coherent interface exhibits greater charge transfer and stronger covalent metal bonds, while the Al(B)-terminated semi-coherent interface shows less charge transfer and more pronounced metallic bond characteristics. These computational insights provide valuable theoretical understanding of interfacial bonding mechanisms inherent in ceramic-reinforced AMCs.