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Phase Transformation Behavior of Al2O3 Scale Formed on Pt-Modified γ'-Ni3Al-Based Alloys With and Without Hf Addition
| 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 www.springerlink.com |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/49357 |
| 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)
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Submitter: 林 重成
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