Grain Boundary Segregation of Boron and Microstructure Evolution in IF Steel at Different Strain Rates

Grain boundary segregation (GBS) of boron and microstructure evolution in IF steel during the process of thermoplastic deformation at different strain rates were studied by using Gleeble-1500 thermo-mechanical simulation testing machine, auger electron spectroscopy and electron backscatter diffraction system. The results show that boron can segregate, significantly, at the ferrite grain boundaries in IF steel with boron during the process of thermoplastic deformation. With the decrease of strain rate, the concentration of supersaturated vacancy in the specimen decreases, and the content of low ∑CSL boundaries in the specimen increases, leading to the decrease in the amount of GBS of boron. Furthermore, the decrease of strain rate promotes the occurrence of dynamic recrystallization in the specimen and refines the grains, which also results in a reduction in the content of GBS of boron, to some extent. The grain orientation changes from [100]//ND to [111]//ND as the increase of strain rate, for maintaining the continuity of the specimen during the process of thermoplastic deformation.