Modelling the transient liquid phase bonding behaviour of a duplex stainless steel using copper interlayers

Analytical models for isothermal solidification and homogenisation stages were applied to the TLP bonding of a duplex stainless steel using copper interlayers to estimate the time for completion of these stages and compare them with experimental results. Diffusivities of copper in iron representing different diffusion mechanisms (lattice diffusion, grain boundary diffusion, and contribution of both) were considered. Good agreement between time for isothermal solidification and experimental results was obtained when an effective diffusivity, estimated as a geometric mean of lattice and grain-boundary diffusivities in α-ferrite was used, indicating that lattice and grain boundary diffusion through the α-phase play an important role in the TLP bonding process of a duplex stainless steel using copper interlayers. However, the model for the homogenisation stage deviates from experimental results as the concentration of Cu at the joint region attains a value close to that of the base metal.