Eutectic structures in Ag-based brazing filler metals play an important role in improving the properties of alloys and brazed joints. The typical microstructures and morphological evolution of Ag-Cu eutectic structures in Ag-based brazing filler metals solidified at various cooling rates and with the addition of different Sn contents were investigated. The formation mechanisms of anomalous eutectic structure (AES) and the morphological transition from lamellar eutectic structure (LES) to AES were elucidated. The microstructures in alloys solidified at a slow cooling rate and with low Sn content consisted of the full AES, which was attributed to the remelting of the LES during recalescence. Increasing the Sn content and cooling rate promoted the formation of developed Ag dendrite, eutectic dendrite with branches, and AES with large dimensions. The AES in rapidly solidified filler metals with a high Sn content was ascribed to the decomposition of the Ag-rich dendrite skeleton and the growth of Cu-rich between the ternary dendrite arms.

In this paper, the interfacial stabilities of six different stacking interface configurations of Ni(100)/Ni₃Al(100) eutectic structures with AlNi termination and Ni termination are calculated by using first-principles methods. The calculated adhesion work and interface energy indicate that the “Center” site stacking interface configurations are more stable than the “Top” and “Bridge” site stacking interface models. The partial density of states (PDOS) and the charge density difference confirm that the bonding characteristic of the Ni-terminated “Center” site stacking interface of the Ni(100)/Ni₃Al(100) eutectic structure is metallic, while the bond at the AlNi-terminated “Center” site interface is a combination of covalent and metallic bonds. A comprehensive analysis of the interface energy, PDOS and charge density difference confirms that the AlNi-terminated “Center” site stacking interface configuration of the Ni(100)/Ni₃Al(100) eutectic structure is the most stable eutectic interface model.