Atomic Scale Investigation of Interfacial Damage Initiation in SnPb Alloy: Structural Stability and Defect-Interface Interactions

In this paper, the initiation of interfacial damage in SnPb alloy was investigated at the atomic scale through molecular dynamics simulations. The focus was primarily on the structural stability of the Sn/Pb interface with different orientations, the formation energies of vacancies in different Sn/Pb interfaces, and the short-range interactions between dislocations and the Sn/Pb interface. The results revealed a correlation between the interfacial energies of all four Sn/Pb interfaces and the disorder of Sn and Pb atoms near the interface, where a more regular atomic arrangement resulted in lower interfacial energy. The vacancy formation energies near the Sn/Pb interfaces varied depending on the interface type, although all types contributed to reducing these energies. Furthermore, the Sn/Pb interface acts as a barrier to dislocations in both Pb and β-Sn phases, while leading to the cross-slip of screw dislocations in the Pb phase. Edge dislocations in the β-Sn phase induce significant strain localization at the interface, initiating interfacial damage and crack nucleation. These findings are highly significant for understanding damage mechanisms in SnPb alloy and advancing high-performance solder development.