Microstructure and Texture Evolution during Recrystallization of Interstitial Free Steel

The evolution of microstructure and texture due to recrystallization was investigated in cold rolled interstitial free (IF) steel. Samples taken from the cold band of a 0.07%Ti bearing IF steel with total cold rolling reduction of 75% were investigated by using optical microscopy, X-ray diffraction and electron back-scattered diffraction etc. The aim of this study was to obtain a real picture of the formation of the recrystallization texture of IF steel, which would contribute to proper texture control for improving deep drawability. The mechanism responsible for the evolution of texture is discussed experimentally from four aspects. First of all, the microstructure of partially annealed cold rolled specimen is obtained. The recrystallized grain form earlier in more darkly etched regions from the micrographs, which belong to the ND//< 111 > fiber components. In addition, the fractions of the {111}< 110 > and {111}< 112 > components increase slowly during the early stage of recrystallization, because the gamma-fiber recrystallized texture is growing, while at the same time the gamma-fiber deformed texture is being consumed. Moreover, The texture formation has been discussed taking into consideration of the stored energy and the misorientation between the orientation of the recrystallized grain and that of the surrounding deformed matrix. The work indicates that the recrystallized grains, which migrate into the deformed grains, are mainly with the high misorientation angles. The large percentage of the recrystallized grains, whose misorientation angles with deformed grains exceed 15 degrees, are corresponding to the {111} transformation texture. Nucleation first starts at colonies that have the highest stored energy of deformation, which has the same orientation as the deformed grains. By analysis, the formation of recrystallization texture was well explained by oriented nucleation mechanism rather than by selective growth mechanism.