Interface structure of N₂-shielded furnace brazing of Al foam and its mechanical properties

N₂-shielded furnace brazing of Al foam was studied experimentally and the microstructure of brazing interface and elements distribution were analyzed by SEM, EDS and optical microscope. Furthermore, morphology of brazing zone was observed by scan model of X-CT and the 3D image of interface was reconstructed.The mechanical properties and the relationship between joint strength and porosity of Al foam were also investigated.The results show that the brazing method does not change the pore structures of Al foam in brazing zone.The brazing interface consists of the intersection points between cell walls of two Al foams and the microstructure in the middle of brazing zone is Al-Si eutectic while near the interface is the α_Al dendrite.The tensile strength of joint closes to that of the base.Brazed area of interface increases with increasing of the Al foam plateau amount, which matches well with the theoretic calculation results when the porosity is over 88%.