NbC precipitation during multi-pass deformation of a nickel-based model alloy: Experiments and modelling

Precipitation behavior during multi-pass deformation has been investigated in a 70Ni-30Fe-Nb-C model alloy. Specimens were deformed at room-temperature and subjected to interrupted annealing at 700 degrees C for different time. Microhardness was performed for each as-deformed/annealed condition, including the initial as-received material. The dislocation structures, as well as, the spatial and size distribution of precipitates have been studied by transmission electron microscopy. The results indicate that the nucleation of precipitates is inhomogeneous due to heterogeneities within the as-deformed microstructure. The main feature is the formation of microbands (about 0.1 mu m-0.5 mu m in thickness) and dislocation tangles/cell structures. The formation of precipitates was observed only after the first pass during the multi-pass deformation and annealing process. Precipitates underwent growth and coarsening processes with increasing annealing time. The volume fraction, radius and number density of precipitates from our experimental work show good agreements with the precipitation model predictions.