NbC precipitation during two-pass hot deformation of a nickel-based model alloy at 700 °C: Experiments and modelling

摘要

Precipitation behavior during two-pass hot-deformation has been investigated in a 70Ni-30Fe-Nb-C model alloy. Samples were deformed at 700 °C and annealed for different times after each deformation pass. The deformed microstructure consisted of cell-like dislocation structures as well as ill-defined microbands and dislocation tangles. Annealing resulted in recovery, with no evidence of recrystallization. Precipitates nucleated heterogeneously on dislocations only after the first deformation pass. A physics-based nucleation, growth and coarsening model was used to rationalize the precipitation behavior. The analysis suggests that precipitation does not take place after the second pass due to the depletion of the thermodynamic driving force. Even when precipitate nucleation is possible after the second pass, the newly formed precipitates quickly become subcritical and dissolve due to the presence of large precipitates that formed after the first deformation pass.