The Effect of Oxygen Potential on the Surface Self-Diffusion Coefficient of α-Fe

• Nii Kazuyoshi

  National Researsh Institute for Metals

• Yoshihara Kazuhiro

  National Researsh Institute for Metals

書誌事項

タイトル別名

• The Effect of Oxygen Potential on the Surface Self-Diffusion Coefficient of α-Fe

抄録

The surface self-diffusivity of α-Fe was measured by the grain boundary grooving method in hydrogen atmospheres with dew points of 213 and 286 K . The groove width measurement was made through all runs with the same region of grain boundary of coarse-grained specimens. The diffusion anneal was carried out at 1073, 1123 and 1163 K.<BR>In dry hydrogen (dew point=213 K) purified through a palladium foil, the surface self-diffusivity of α-Fe can be expressed by the following equation:<BR>D_s=10exp(−228kJ⁄RT)(m²·s⁻¹).<BR>The value of activation energy agrees well with that obtained by Blakely et al.<BR>In moist hydrogen (dew point=286 K), however, the rate of groove development was varied, depending on whether or not the specimen had been equilibrated with the atmosphere. When the specimen, which had been in equilibrium with dry hydrogen, was annealed in moist hydrogen, the rate of groove development was larger than that in dry hydrogen in the early stage, but it decreased with annealing time. On the other hand, if the specimen had been equilibrated with the same atmos-phere, the grooving rate was smaller than that in dry hydrogen. In the former case, surface roughening would occur more than in thermal equilibrium owing to the adsorption and solution reactions of oxygen at the surface, which would lead to an enhancement of surface diffusivity. On the contrary, on the surface of the specimen, which is equilibrated with moist hydrogen, the blocking of kink and ad-atom would occur by adsorption of oxygen, which would lower the surface diffusivity.<BR>A marked decrease in surface diffusivity in hydrogen with a dew point of 286 K was observed at 1073 K with the specimen equilibrated with the same atmosphere, which could be attributed to an incidental adsorption of impurities during the sample preparation.

収録刊行物

• Transactions of the Japan Institute of Metals

  Transactions of the Japan Institute of Metals 20 (9), 523-532, 1979

  社団法人 日本金属学会

キーワード

• General Engineering

詳細情報

• CRID: 1390001205117608320
• NII論文ID: 130003485783
• DOI: 10.2320/matertrans1960.20.523
• COI: 1:CAS:528:DyaL3cXotValtw%3D%3D
• ISSN: 24324701
• ISSN: 00214434
• Web Site: https://www.jstage.jst.go.jp/article/matertrans1960/20/9/20_9_523/_pdf
• 本文言語コード: en
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