The {0 1 1 }/{0 1 1} near singular boundaries in 00Cr12 ferritic stainless steel after rolling and recrystallization
Different from the low stacking fault energy(SFE)face-centered cubic(FCC)austenitic stainless steels,high SFE body-centered cubic(BCC)ferritic stainless steels are hardly to produce structure-stable and corrosion-resistant singular boundaries or namely the coherent twin boundaries during recrystallization after deformation.To investigate the so-called {0 1 1 }/{0 1 1} near singular boundaries will be significant to the grain boundary engineering(GBE)approach to better the performance against intergranular corrosion(IGC)in the ferritic stainless steels,especially in the low Cr ferritic stainless steels.In the current work,the solid-solution-treated and microstructure-uniformed 00Crl2 low Cr ferritic steel were chosen as experimental materials.Five parallel samples were rolled respectively at 350℃,500℃,580℃,650℃ and 690℃ followed by 2 h recrystallization annealing at 750℃.The method of grain boundary inter-connection(GBIC)characterization based on electron backscatter diffraction(EBSD)and five parameter analysis(FPA)was used to determine the content of {0 1 1 }/{0 1 1} near singular boundaries in the processed samples.It is found that the preceding rolling temperature has a significant impact on the formation of {0 1 1 }/{0 1 1} near singular boundaries during subsequent annealing at 750℃.The fraction of {0 1 1 }/{0 1 1} near singular boundaries after recrystallization is increasing at first and then decreasing when the preceding rolling temperature increasing from 350℃ to 690℃.The sample rolled at 650℃ followed by annealing at 750℃ has a peak content of {0 1 1 }/{0 1 1} near singular boundaries and the fraction reaches 6.82％,which is about 10 times higher compared to that of the singular boundaries.Orientation distribution function(ODF)and over-lapped pole-figure boundary trace analysis indicate that a strong {0 1 1}<0-1 1>texture is developed in the sample rolled at 650℃ followed by annealing 750℃.Quite a few grains of {0 1 1 }<0-1 1>orientation,including its diffuse orientation,have<0 1 1>/θ misorientation(θ is a rotation angle around<0 1 l>)with each other,and the relevant grain boundaries are {0 1 1 }/{0 1 1} near singular boundaries.This is the reason why the sample rolled at 650℃ followed by annealing 750℃ has a peak content of {0 1 1 }/{0 1 1} near singular boundaries.Off-line in-situ surface etching test demonstrates that the {0 1 1}/{0 1 1} near singular boundaries are much more resistant to corrosion compared to random boundaries.Based on the present results,to regulate the {0 1 1 }/{0 1 1} near singular boundaries will be promised for bettering the performance against IGC in 00Cr12 ferritic stainless steel.
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