  In joining Fe-alloys and Cu-containing alloys to access the high strength of
steels and corrosion resistance of Cu-alloy, cracking is widely observed due to
the significant Cu microsegregation during the solidification process,
resulting in an interdendritic Cu-rich liquid film at the end of
solidification. By fabricating functionally graded materials (FGMs) that
incorporate additional elements like Ni in the transition region between these
terminal alloy classes, the hot cracking can be reduced. In the present work,
the joining of stainless steel 316L (SS316L) and Monel400 by modifying the Ni
concentration in the gradient region was studied. A new hot cracking criterion
based on hybrid Scheil-equilibrium approach was developed and validated with
monolithic multi-layer samples within the SS316L-Ni-Monel400 three-alloy system
and an SS316L to 55/45 wt% SS316L/Ni to Monel400 FGM sample fabricated by
direct energy deposition (DED) process. The new hot cracking criterion, based
on the hybrid Scheil-equilibrium approach, is expected to help design FGM paths
between other Fe-alloys and Cu-containing alloys as well.
