The {111}∥ND plane texture,grain boundary characterization and grain boundary segregation of phosphorus are investigated for the phosphorus added high strength interstitial free(IF)steel annealed at 810℃ for 60 s to 180 s.The results show that the maximum volume fraction of {111}∥ND plane texture is about 85% and the grain boundary segregation peak of phosphorus is about 14 at.%for the steel annealed at 810 ℃ for 120 s.The Σ3 and other low-ΣCSL(coincident site lattice)boundaries are lowest for the steel annealed for 120 s.Segregation of phosphorus is also found at low angle grain boundaries.
Xin-li SONGKun PENGZe-xi YUANJuan JIAJing LIULi-xia FAN
The precipitation behavior of FeTiP in interstitial free high strength(IFHS)steels has been studied by using a transmission electron microscope(TEM).The results show that the TiC particles,appearing at earlier stage,are more stable than the FeTiP ones during recrystallization annealing at the two given temperatures(810℃ and 840℃).Therefore,the FeTiP particles can only be observed in the steels with sufficient amount of Ti.There is a critical forming time for the FeTiP,which is between 90-120 sat 810 ℃ and 60-90 sat 840 ℃.The precipitation of FeTiP involves two steps,i.e.the formation of FeTi precursors and the diffusion of P.The former step determines the reliance of Ti content for the precipitation of FeTiP,whereas the latter step leads to the difference in the critical annealing time.
High-strength interstitial-free steel sheets have very good deep drawability when processed to have{111}recrystallization texture.The microtexture evolution and grain boundary character distribution of interstitial-free steels as a function of moderate levels of cold rolling reductions were investigated by the metallographic microscopy and electron backscatter diffraction technique.The results showed that there was a close relationship between microtexture and grain boundary character distribution for interstitial-free steel,especially the distribution and features of some specific types of coincident-site lattice boundaries.In addition,α-fiber texture was weakened to vanish whileγ-fiber texture strengthened gradually as cold rolling reduction was increased from 20%to 75%for cold rolled and annealed samples.Accordingly,increasing the rolling reduction from 20%to 75%would lead to a significant increase in the proportion ofΣ3boundaries.Also,it was found that the microtexture of 20%cold rolled sample would induce a high frequency ofΣ11grain boundaries,but the microtexture of 75%cold rolled sample would produce moreΣ7andΣ17grain boundaries.It was suggested that texture played a significant role in the formation of grain boundary character distribution.
YANG Jing-jingFAN Li-xiaJIA JuanWU RunSONG Xin-liJIANG Li-li
