Effects of Cerium Content on the Nonmetallic Inclusions and Impact Toughness of Transformation‐Induced Plasticity Steel

Abstract

The effects of Ce treatment on the inclusion evolution and impact toughness of as‐cast transformation‐induced plasticity (TRIP) steel are systematically investigated by scanning electron microscope (SEM) and impact toughness testing. The results reveal that in Fe‐2Mn‐1.5Al‐1Si‐0.2C steel without Ce, the primary inclusions consist of AlN, MnS, and Al2O3. After Ce addition, the inclusions evolve into Ce‐Al‐O, Ce2O2S, CeS, and Ce2O3 inclusions. The evolution of inclusions exhibits an initial reduction in both quantity and size with increasing Ce content, followed by a subsequent increase. In cases of excessive Ce content, there is an observable rise in the overall inclusion count, marked by the emergence of CeAs, CeP, and CeC2 inclusions. The segregation model suggests that P‐containing inclusions predominantly precipitate in the late solidification process, while As‐ and C‐containing inclusions form during the solid phase. When the Ce content reaches 0.0075 wt%, the minimum values of the number density and average diameter are 96.7 mm−2 and 1.6 μm, respectively. Furthermore, the influence of the size, morphology, quantity, and type of inclusions on the impact toughness are analyzed. The highest recorded impact energy is 6.8 J with a Ce content of 0.0075 wt%.