Analytical electron microscopy of internally oxidized low Si-Al steel

Abstract

Analytical electron microscopy was used to study the precipitates in internally oxidized low Si-Al steels, of the type used for electric motor laminations. After oxidizing heat treatments of one and five hours at 788 °C, the internally precipitated particles were about 0.1 to 0.2 μm in diameter. At the internal-oxidation reaction front, thin plates of Al2O3 precipitated. Subsequently, a shell of SiO2 precipitated on the Al2O3 core. Depth of internal oxidation was predicted from the knowledge of precipitate composition, treatment time and temperature, and published information.