Simultaneous creep and oxidation of an Fe-1 wt pct Ai alloy at 973 to 1073 K

Abstract

Studies of the simultaneous creep and oxidation of an Fe-lwt pct Al alloy at constant stresses of 16 to 26 MN/m² in the temperature range 973 to 1073 K have shown that the steady state creep obeys a power law. The stress exponentn was found to be 6.9 for creep in an argon atmosphere (Po₂ = 10⁻³ mbar). Values of the apparent activation energy for creep were in the range 225 to 351 kJ/mol and appeared to be dependent on the P_{0 2} of the test environment. Oxidationstrengthening (ġe decreasing) occurred at 998 K but only at P_{0 2} = 10⁻3 mbar and was primarily due to intergranular oxidation and the mechanical constraint of a strongly adherent scale. Oxidationweakening (ġe increasing), however, occurred at 973 to 1073 K in environments of the lowest P_{0 2} (10⁻⁹ and 10⁻⁵ mbar) and in the highest P_{0 2} (162 to 1013 mbar). The factors contributing to weakening are believed to be oxidation-induced vacancies, weakly adherent scales and the loss of solute strengthening aluminum through selective oxidation.