Carbide precipitation kinetics in austenite of a Nb-Ti-V microalloyed steel

The isothermal precipitation kinetics of carbides in both strain-free and strained austenite (gamma) of a microalloyed steel were quantitatively investigated through the electrical resistivity and transmission electron microscopy. The (Nb,Ti)C carbides at the interfaces of the undissolved (Ti,Nb)(C,N) carbonitrides were observed at all temperatures in strain-free gamma. However, for strain-induced precipitation, above 950 degrees C, the precipitation of (Nb,Ti)C carbides near the undissolved (Ti.Nb)(C,N) carbonitrides was predominant due to the recrystallization of strained gamma. Meanwhile, the fine (Nb.Ti,V)C carbides were homogeneously precipitated in non-recrystallized gamma at 850 degrees C and 900 degrees C, as well as near the undissolved (Ti,Nb)(C,N) particles. The electrical resistivity method was successfully used to quantitatively measure the isothermal precipitation kinetics of carbides in both strain-free and strained gamma. The precipitation-time-temperature diagrams of the carbide in strain-free and strained with nose temperatures of 950 degrees C, were generated and the precipitation kinetics were greatly accelerated by the applied strain. (C) 2011 Elsevier B.V. All rights reserved.