Effect of Manganese segregation behavior on the wettability of the AgCu/ FeCoNiCrMn high-entropy alloy system: First-principle calculations and experimental investigation

The influence of manganese segregation in FeCoNiCrMn high entropy alloy (HEA) on the high-temperature wetting behavior of Ag-Cu filler on HEA substrate has been investigated through first-principles calculations and experimental investigation. The Mn will prefer to segregate at the surface of high entropy alloy, and exhibits the most pronounced interaction with Ag-Cu liquid droplets during the high-temperature wetting process. First-principles calculations of the Ag/HEA interface with 1 % Mn segregation reveal a work of adhesion ranging from 1.82 J/m² to 2.05 J/m². This interfacial bonding strength further increases with higher Mn segregation levels. Mn segregation significantly modifies the electronic structure of both the HEA surface and the Ag/HEA interface. Interfacial models were developed to investigate the contrasting behaviors of Mn (acting as an enrichment element) and Cr (serving as a reactive element) in their interfacial interactions with Ag. Notably, Mn variation demonstrates consistently lower energy than Cr variation in all studied systems. The Mn variation systems own substantially lower energy, while the Cr variation system own higher work of adhesion improving interfacial bonding strength. Experimental results demonstrate that increasing the wetting temperature from 800 °C to 900 °C enhances wettability, reducing the contact angle from 15° to 0° while shortening the equilibrium time from 550 s to 250 s. The Energy Dispersive Spectroscopy (EDS) analysis of the wetting cross-section after high-temperature wetting reveals significant elemental segregation at the interface, characterized by a marked reduction in Mn content and a concurrent enrichment of Cr, which exhibits excellent agreement with theoretical predictions.