Dissolution and Precipitation Kinetics of Nb(C,N) in Austenite of a Low-Carbon Nb-Microalloyed Steel

The dissolution and the precipitation kinetics of Nb(C,N) particles in both strain-free and strained austenite of a low-carbon Nb-microalloyed steel were investigated using electrical resistivity, interrupted compression, and electrolytic dissolution methods as well as transmission electron microscopy (TEM). The dissolution temperature of the 0.08C-0.038Nb steel was determined to be about 1230 °C for 600 seconds using electrical resistivity method and was confirmed by TEM. With increasing strain, the isothermal precipitation kinetics of Nb(C,N) was accelerated and the particle distribution became more random. The precipitation-time-temperature diagrams of the Nb(C,N) precipitates in strain-free and strained austenite were generated between 850 °C and 950 °C. The nose temperatures for both diagrams were about 900 °C. Compared to the electrolytic dissolution method, the interrupted compression and electrical resistivity methods show more reasonable strain-induced precipitation kinetics. The electrical resistivity method has wider applications to the dissolution and precipitation kinetics in microalloyed steels.