The influence of grain size of alloy MA 956 on the oxidation kinetics and scale morphology is investigated at 900 and 1100℃ for up to 1000 h exposure. Specimens with grain sizes of about 3, 150, and 300μm mean diameter were studied. Grain growth during oxidation was not observed. The results of this work at 1100℃ show that grain size of the alloy does not significantly influence the oxidation kinetics. At 900℃, however, mass gain values for the small-and medium-cram size material are somewhat lower than those for the large-grain size material, especially for exposures below 100 h. This feature indicates that grain boundaries could have played a role for the supply of Al to the scale.
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