Inclusion and microstructure characteristics in steel with TiO2 nanoparticle additions

Abstract

Abstract TiO2 nanoparticles were directly added to molten steel. The corresponding analyses of inclusion and microstructure were carried out through scanning electron microscopy (SEM) and an energy-dispersive X-ray spectrometer (EDS). On the one hand, a large number of micrometer scale Ti-bearing inclusions were observed. Besides Ti, other elements, such as Al, Mn, Si and S, were present in these inclusions. These phenomena not only confirmed the validity of adding TiO2 nanoparticles but likewise their growth and reactivity. This can be explained by the interaction between TiO2 and a Fe matrix, the decomposition reaction of TiO2 and a higher Gibbs free energy for the nanoparticles. On the other hand, these Ti-bearing inclusions can induce the nucleation of intragranular acicular ferrite. This is similar in appearance to a Ti-bearing inclusion originating through internal precipitation and may be explained by the theory of a Mn-depletion zone.