Deformation of Iron Oxides upon Tensile Tests at 600–1250°C

Abstract

Tensile tests of virtually “pure” FeO, γ -Fe₃O₄, and α-Fe₂O₃ were performed at 600–1250°C at strain rates of 2.0×10⁻³–6.7×10⁻⁵ s⁻¹ under controlled gas atmospheres. Mechanical properties and deformation/fracture behavior were investigated. For α-Fe₂O₃, brittle fracture resulted at 1150–1250°C, and the fracture strain was below 4.0% at a strain rate of 2.0×10⁻⁴ s⁻¹. Oxide of γ -Fe₃O₄ deformed plastically above 800°C. Steady-state deformation was indicated at 1200°C; elongation of 110% was obtained. Plastic deformation observed at 800–1100°C was considered to result from dislocation glide. Using TEM, burgers vector of dislocation observed in deformed γ -Fe₃O₄ was determined to be 〈110〉, and its slip system was estimated to be {111}<110>. Oxide of FeO deformed plastically above 700°C. Steady-state deformation became predominant above 1000°C. Elongation of 160% was obtained at 1200°C. Strain rates of FeO at 1000 and 1200°C were proportional to the fourth power of the saturated stress, indicating that the plastic deformation was affected by dislocation climb.