Effect of two-step heating process on joint microstructure and properties during transient liquid phase bonding of dissimilar materials

This paper investigates a novel two-step heating process to transient liquid phase (TLP) bond dissimilar steels between 45MnMoB and 30CrMnSi. The process consists of a short-time high temperature heating followed by isothermal solidification at a lower temperature. The microstructure and mechanical properties of the bonds were investigated and compared with that of conventional TLP bond made at a constant bonding temperature. The results show that the two-step heating process can change the interface morphology from planar to non-planar and increase the curvature of the non-planar interface during TLP bonding. The voids are decreased and the bending strength is increased with the increase of isothermal solidification temperature during two-step TLP bonding. Compared to conventional TLP bonding, the two-step heating can reduce the voids and improve the bond strength near similar bonding temperature within minutes. Production tests show that the two-step heating has the potential application in industry. Modeling of interface morphology and defects in the joint are also discussed.