CMnAl TRIP Steel Surface Modification During CGL Processing

摘要

The mechanisms of selective oxidation of intercritically annealed CMnAl TRIP steels in a Continuous Galvanizing Line (GCL) were studied by cross-sectional observation of the surface and sub-surface regions by means of High Resolution Transmission Electron Microscopy (HR-TEM). The selective oxidation and nitriding of an intercritically annealed CMnAl TRIP steel in a controlled dew point 10%H_2+N_2 atmosphere resulted in the formation of c-xMnO.MnO_2 (1≤x≤3) and c-xMnO.Al_2O_3 (x≥1) particles on the steel surface. Single crystal c-xMnO.SiO_2 (2≤x≤4) oxide particles were also observed on the surface. A thin film of crystalline c-xMnO.SiO_2 (2≤x≤3) and c-xMnO.Al_2O_2 (x≥1) was present between these particles. In the sub-surface region, internal oxidation, nitriding and intermetallic compound formation were observed. In the first region, large crystalline c-xMnO.SiO_2 (1≤x≤2) and c-xMnO.Al_2O_3 (x≥1) oxides particles were present. In the second region, c-AlN particles were observed, and in a third region, small MnAl_x (x>1) intermetallic compound particles were observed.