Investigation of the Thermal Deformation Behavior Exhibited by Oxidation Products in Fe–Si Alloys

Abstract

The thermal deformation behavior of oxidation products formed on Fe–Si alloys with varying Si contents was systematically investigated using a thermal simulation testing machine during compressive deformation at temperatures ranging from 800 to 1100 °C. It is found that the higher the deformation temperature is, the better the plasticity of the oxide product is, and the better the deformation coordination between the oxidation product and the substrate, where the deformation mainly occurs in the FeO layer. The increase of Si content reduces the coordination of deformation between the oxidation product and the substrate, but it can improve the interface straightness. The crystal structure of the oxidation product determines its plastic deformation ability, and the deformation mechanism of FeO is determined by the dislocation slip and climb, and its plastic deformation ability is the best. The dislocation slip dominates the deformation mechanism of Fe₃O₄, and the deformation ability is the second, and Fe₂O₃ has basically no plastic deformation ability. Therefore, the increase of the Si content leads to the reduction of the proportion of the FeO layer in the oxidation product, which is the main reason for the decrease of the deformation coordination between the oxidation product and the substrate. As Si element forms a spinel solid solution composed of Fe₂SiO₄ with FeO and SiO₂ at the interface, it has good plastic deformation ability and can deform synchronously with the substrate, and the porous structure can effectively relieve the compressive stress during deformation, which can effectively improve the interface straightness. In addition, the increase of Si content makes the concentration of iron ions in FeO close to the substrate side lower, which causes the increase of point defect concentration to promote the dislocation climbing of FeO, and makes the steady-state plastic deformation ability of FeO close to the substrate side higher, which improves the straightness of the interface between the oxidation product and the substrate.