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Phase Transformation Behavior of Al2O3 Scale Formed on Pt-Modified γ'-Ni3Al-Based Alloys With and Without Hf Addition

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Title: Phase Transformation Behavior of Al2O3 Scale Formed on Pt-Modified γ'-Ni3Al-Based Alloys With and Without Hf Addition
Authors: Hayashi, Shigenari Browse this author →KAKEN DB
Gleeson, Brian Browse this author
Keywords: Hf effect
Al2O3 phase transformation
Grain growth
Short-term kinetics
Issue Date: Jun-2012
Publisher: Springer Netherlands
Journal Title: Oxidation of Metals
Volume: 77
Issue: 5-6
Start Page: 237
End Page: 251
Publisher DOI: 10.1007/s11085-012-9282-x
Abstract: The allotropic phase transformation behavior of Al2O3 scale formed on Ni-22Al-30Pt (in at.%) with and without 0.5Hf was investigated during short-term (i.e., 3 min dwell) cyclic oxidation at 1150℃ in air. Hafnium addition did not appear to affect the oxidation rate in the early oxidation cycles, but it did delay the phase transformation from the metastable θ-Al2O3 structure to the stable α-Al2O3. Small dimples, which corresponded to α-Al2O3 grains, started to form on the Hf-free alloy after only 3 oxidation cycles; whereas, no apparent morphological change of the oxide scale surface was observed on the Hf-modified alloy. The transformation to α-Al2O3 was found to initiate at scale/alloy interface on the Hf-free alloy, but it initiated at gas/scale interface on the Hf-modified alloy. Depth profiling using glow discharge optical emission spectroscopy revealed that Hf enriched at the scale/alloy interface due to Hf rejection associated with the formation of an Al-depleted γ-layer, which has a low Hf solubility. Higher positive strain energy due to Hf solution in the metastable Al2O3 was inferred to be the main contributor to the delayed the transformation.
Rights: The final publication is available at
Type: article (author version)
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 林 重成

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