Inclusion and microstructure characteristics in steel with TiO2 nanoparticle additions

Abstract TiO 2 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 TiO 2 nanoparticles but likewise their growth and reactivity. This can be explained by the interaction between TiO 2 and a Fe matrix, the decomposition reaction of TiO 2 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.