The Study Of γâ†'α Transformation And Carbide Precipitation In Fe-C-Mo Alloy With Compressive Deformation

Grain refinement is a unique method to improve steel's strength and increase steel's toughness, which is always the hotpoint in steel studies. Deformation process is the one of most effective methods for grain refinement. Deformation process application for more excellent performance of steel has become the development trend in iron and steel industry. Thus, the effects of deformation on phase transformation and carbide precipitation are necessarily studied for depth.Compressive deformation tests were performed on a Gleeble-3500 thermal mechanical simulation testing system, followed by isthermal holding for different time at different temperatures. By means of optical microscope, SEM and TEM, the effects of compressive deformation onβ→αtransformation and carbide precipitation were investigated. The analysis and discussion on results of experiments were made from the view points of phase transformation thermodynamics and kinetics. The main conclusions are as follows:The formation of deformation bands, dislocations and sub-structures accelerated nucleation kinetics of ferrite as a result of an increase in nucleation sites. Deformation potency increased the driving force of nucleation. But the substructures prevented ferrite from continuous growth. Grains were obsvious refined and percentage of phases transfomed decreased. The transformation temperature of austenite to ferrite was shifted to higher one and incubation period was reduced. The TTT curves were moved to left and upwards. The bay temperature range and depth were decreased. The bay temerature was raised to 590℃from 570℃.Carbide precipitions formed along th edislocation and sub-grain boundaries fomed as a result of an increase in nucleation sites of carbides. Deformation potency increased the driving force of nucleation of carbides. Carbide particles were obsviously refined and much more diffused. Plate-like Fe3C, needle-like or rod-like (Fe,Mo)2C,lath-like (Fe,Mo)3C and spherical (Fe,Mo)6C were precipited after isothermal holding at 700℃,610℃and 530℃. The sequence of carbide precipitation did not changed, which was Fe3C→(Fe,Mo)2C→(Fe,Mo)3C→(Fe,Mo)6C.