Investigation on Precipitation Behavior and Morphology of TiN Particles in High-Ti Low-Carbon High-Strength Steel

Abstract

The precipitation behavior of TiN particles under homogeneous and heterogeneous nucleation conditions in a low-carbon high-strength steel with 0.11 wt% Ti was investigated by thermodynamics and dynamics equations combining with the microstructural observations on the surface and at the core of the casting slabs. The effect of cooling rate on the morphology and dimension of TiN particles was also analyzed in the present study. In addition, the three-dimensional and the spatial tridimensional morphology of compound TiN–Al2O3 was innovatively characterized by a focused ion beam scanning electron microscope. It was found that TiN particles possessed inerratic facet morphology (such as squares and clusters), and the square morphology was predominant. The preferential plane for TiN precipitates in the tested steel was {100}. Moreover, TiN particles precipitated both in solid and liquid phases from the solid–liquid phase region during the solidification process, and preferential precipitation was observed in the solid phase. Furthermore, the size of TiN particles decreased with the increasing cooling rate during the casting process. Al2O3 particles provided nucleation sites for the heterogeneous nucleation of TiN particles.