Reactive wetting between molten Sn-Bi and Ni substrate

Abstract

Wetting and interfacial reactions occurred when molten Sn-Bi alloys were in contact with a Ni substrate. Wetting properties of Sn-Bi alloys on the Ni substrate and their interfacial reactions were examined, and the effects of interfacial reactions on wetting properties were discussed. Couples made of various molten Sn-Bi alloys and Ni substrates were reacted at 300°C. It was found that, when the Bi content was greater than 98 wt.%, the intermetallic phase formed at the interface was NiBi3 phase. The Ni3Sn4 phase was found in the other Sn-Bi/Ni couples that had Bi contents varied from 92 wt.% to 97.5 wt.%. An isothermal section at 300°C for the ternary Sn-Bi-Ni system was proposed to illustrate the reaction paths of Sn-Bi/Ni couples. Wetting properties, including wetting time and wetting force of molten Sn-Bi alloys, were determined by using a wetting balance. Surface tensions at 300°C were calculated based on the experimental measurements. For molten Sn-Bi alloys with Bi contents varying from 92 wt.% to 99 wt.%, their surface tensions were all about 0.34 N/m. On the basis of theoretical analysis and experimental observations, the surface tensions of molten metals, determined by using the wetting balance, are not significantly affected if the interfacial reaction is not excessive. However, the wetting time determined by using the wetting balance was altered by the reaction that occurred and the compound formed at the interface.