Influence of Grain Refinement on Oxidation Behavior of Two-Phase Cu-Cr Alloys at 973-1,073 K in Air

Abstract

The oxidation behavior of grain-refined Cu-7.0 Cr alloy (GR Cu-7.0 Cr) in air at 973-1,073 K was investigated in comparison with normal casting Cu-7.0 Cr alloy (CA Cu-7.0 Cr). The oxidation of CA Cu-7.0 Cr alloy nearly followed parabolic law, while the oxidation kinetics of GR Cu-7.0 Cr slightly deviated from parabolic law. Both alloys almost produced multi-layered scales consisting of the outer layer of CuO and the inner layer of mixed Cr2O3 and Cu2O oxides plus internal oxidation zones of chromium. The grain-refined Cu-7.0 Cr alloy produced a more amount of Cr2O3 in the inner layer of the scale, and thus was oxidized at much lower oxidation rate than that of CA Cu-7.0 Cr with normal grain size. The experimental results indicated that the differences in oxidation behavior between two alloys may be ascribed to the different size and spatial distribution of the second-phase particles and the reactive component contents in localized zone.