Effect of Rare Earth Addition on Dynamic Recrystallization and Precipitation Behavior of a Niobium-Containing Microalloy Steel

摘要

Hot compression experiments were carried out on rare earth (RE) added and RE-free Nb-containing steels by using a Gleeble simulator. Stress-strain curves obtained at various temperatures were analyzed to investigate the dynamic recovery and dynamic recrystallization softening behaviours. Morphology, size and number of precipitates in the both steels were examined by means of transmission electron microscopy (TEM). The results showed that, for the experimental Nb-containing steel, the grain size was fined by the RE addtion. In general, dynamic recrystallization can't occur in two steel under 40% deformation rates, and the deformation resistance of RE-containing steel is higher than that of RE-free steel in both the the austenite and ferrite temperatures range.While under the higher deformation rate, the dynamic recovery starting strains of the RE addition steel are higher than that of RE-free steel.lt is also shown that the number of precipitate in the RE-containing steel more than that in the RE-free steel, which is due to the RE increasing nucleation rate and promoting Nb carbonitrides precipitation growth in the austenite region. Furthermore, the carbon activity may change by the RE addition, and thereby promote the precipitation strengthening of Nb-microalloyed steel.