First-Principles Investigation of the Properties of Copper–Aluminum Intermetallic Compounds

After copper and aluminum are connected friction stir welding(FSW), the primary intermetallic compounds formed in the joint are Al4Cu9, Al2Cu, and AlCu. To further analyze the influence of intermetallic compounds on the properties of Cu/Al joints, the mechanical, electronic, and thermodynamic properties of Al4Cu9, Al2Cu, and AlCu in Cu/Al joints were calculated using first-principles methods. Based on the calculated cohesive energy and formation enthalpy, the stability order of the compounds is Al4Cu9 > Al2Cu > AlCu. The energy band structure and density of states indicate that these compounds predominantly form covalent bonds while exhibiting conductive properties. The single-crystal elastic constants and polycrystalline elastic moduli, including bulk modulus, Young’s modulus, and shear modulus were calculated, and the melting points were predicted to understand their respective thermal expansion coefficients.