Characterization Transformation of Inclusions Using Rare Earth Ce Treatment on Al‐Killed Titanium Alloyed Interstitial Free Steel

By using the thermodynamic calculation of evolution of inclusions that contain rare earths, industrial-scale modification experiments are conducted. Energy spectroscopy analysis, field emission scanning electron microscopy, energy dispersive spectrometry, original morphology analysis, and Factsage 7.2 software are used to analyze the evolution mechanisms of inclusions in Al-killed titanium-alloyed interstitial free steel. The results reveal that different substances are formed in the following order: Ce2O3(s) > Ce2O2S(s) > CeAlO3(s) > CeO2 (s), with the wt[%Ce] reaching a range of 0-0.01 according to thermodynamic calculation. After Ce treatment, irregular Al2O3 inclusions with a size of 10-15 mu m are wrapped by rare earth and then gradually modified into spheroidal CeAlO3, Ce2O3, and Ce2O2S inclusions with a size of approximate to 5 mu m and distributed into interstitial free slabs. A geometric model is developed for the formation of oxide inclusions to illustrate the process of modification. The disregistries between the two-dimensional lattice parameters of the nucleating phase (Ce2O3 and Ce2O2S) and the substrate (delta-Fe) at the interfaces are 6.21% and 5.77%, respectively, as measured by modified calculations performed during the heterogeneous nucleation phase.