Interfacial interaction of solid nickel with liquid bismuth and Bi-base alloys

The dissolution process of nickel in liquid bismuth and a 51%Bi-42%Sn-5%In-2%Zn alloy was investigated by the rotating-disc technique at 300 and 350 °C. The solubility values of nickel in bismuth and its alloy were found to be very different, while the dissolution rate constants were rather close. Appropriate diffusion coefficients were estimated. With bismuth as a melt material, the NiBi3 intermetallic layer is formed at the interface of nickel and the saturated or undersaturated melt at holding times up to 3600 s. The NiBi phase is found to be missing. A simple mathematical equation is proposed to evaluate the NiBi3 layer thickness in the case of undersaturated melts. With a 51%Bi-42%Sn-5%In-2%Zn alloy as a melt material, a very thin intermetallic layer of complicated chemical composition occurs at the Ni-alloy interface. With saturated melts, its growth-rate constant is 5.5 × 10−16 m2 s−1 at 350 °C, whereas in undersaturated melts, the intermetallic phase does not form at all, if the liquid agitation is sufficiently strong. The rupture strength of the nickel-to-alloy joints is around 25 MPa. Small additions of Sb, Te and Se (2% in total) to the alloy exert a considerable influence on the intermetallic-layer composition, but have minimal impact on its thickness.