Characterization of Rare Earth Inclusions from Cast 1010 Steel

Abstract

An electron microscopy investigation was conducted on two cast 1010 steel plate samples that had rare earth silicide additions. A scanning electron microscope (SEM) and transmission electron microscope (TEM) with energy dispersive spectrometer (EDS) characterized the inclusions found. The SEM primarily observed rare earth oxide particles. No particles less than 1 μm in diameter were found in the TEM which indicates that any possible heterogeneous nuclei are only about 1 μm in size. Electron diffraction and EDS spectra from the rare earth inclusions examined indicated that they were comprised of multiple rare earth phases. The matrix and one rare earth inclusion with a face centered cubic (FCC) like crystal structure had an eight degree alignment between crystallographic axes. This suggested that the body centered cubic (BCC) structure of ferrite and some of the FCC like rare earth compounds could align with each other. Such alignment would be necessary for any particle to act as a heterogeneous nucleus of δ-ferrite.