Study On The Interfacial Bonding And Mechanical Properties Of SiC And Al₂O₃ Reinforced Al Matrix Composites

As the most common particle reinforced aluminum matrix composites,Al/4H-SiC and Al/?-Al₂O₃ composites have great mechanical properties.However,the influence of interfacial reaction and bonding properties on the mechanical properties is still unclear.In this study,the interface structure,bonding strength and bonding characteristic of the Al(111)/4H-SiC(0001)and Al(111)/?-Al₂O₃(0001)interfaces are investigated based on the first-principles calculations.The microscopic mechanism of interface products and doping regulation on the mechanical properties are analyzed.Interfacial reaction will directly affect the bonding strength,and then affect the mechanical properties of the materials.For the Al/4H-SiC interface,it was found that the interface bonding strength of C-terminated interface is significantly higher than that of Si-terminated.The Al/C interface has the stronger bonding strength which was attributed to the formation of Al₄C₃-like phase.However,the weak bonding strength is caused by the segregation of Si atoms of the Al/Si interface.The first-principles tensile tests show that the tensile properties of the C-terminated interface are better than the Si-terminated,and the ultimate tensile strength is increased by 2.62 GPa and the elongation is increased by 2%.The Al₄C₃-like phase at the Al/C interface shows a great coupling between the matrix and the reinforcement,which facilitates the load transfer,while for the Al/Si interface,the vacancy caused by the segregation of Si atoms can significantly decrease the tensile properties.Doping modulation is an effective method to study and improve the interfacial bonding and mechanical properties.For the Al/?-Al₂O₃ interface,the most stable Al/Al₂O₃ interface comprises Al(111)and Al-terminated Al₂O₃(0001)with OT stacking.Electronic structures indicate the interaction of clean interface is mainly ionic,and yet maintains a small amount of covalent character.First-principles tensile tests show that the critical strain of the Al/Al₂O₃ interface is 18%,and the ultimate tensile strength is 7.37 GPa.For the doped interfaces,there is no direct relation between the mechanical properties and the work of adhesion or the interface energy,and the tensile properties were affected by the uniformity of charge density distribution,which we call the interface intrinsic strengthening mechanism.The systems with more uniform charge distribution during stretching show excellent tensile properties.The results are important to direct the design of metal matrix composites.