高湿度中における高強度Al合金7075-T6押出材の疲労き裂伝ぱ機構

Translated title of the contribution: Growth mechanism of a fatigue crack of extruded high strength Al alloy 7075-T6 in high humidity

皮籠石 紀雄, 仮屋 孝二, 陳 強, 中村 祐三, 永野 茂憲, 王 清遠

Research output: Contribution to journalArticle

Abstract

Effect of humidity on the growth mechanism of a fatigue crack in an age-hardened Al alloy was investigated in relative humidity environments of 25% and 85% at loading frequencies of 50Hz and 6Hz. Macroscopic growth mode of a crack in low humidity was a tensile one irrespective of loading frequency. By contrast, the mode in high humidity was changed from the shear one to the tensile one with increase in fatigue life at 50 Hz, while it was the tensile mode only in the wide range of fatigue life at 6 Hz. In low humidity, the crack propagated by forming striations which are general in fatigue of many metals. On the other hand, in high humidity, most of fracture surface was occupied by many slip planes in the shear mode crack and by granular facets in addition to striations in the tensile mode one. The crack growth rate in high humidity was higher in the shear mode crack than in the tensile mode one. The differences in growth mechanism and growth rate of a crack were explained by the content of diffused hydrogen generated by reaction of water vapor and aluminum in addition to the microstructure with sub-grain and texture and the cyclic softening behavior of the alloy.
Original languageJapanese
Pages (from-to)14-00694-14-00694
Journal日本機械学会論文集
Volume81
Issue number825
DOIs
Publication statusPublished - 2015
Externally publishedYes

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皮籠石紀雄, 仮屋孝二, 陳強, 中村祐三, 永野茂憲, & 王清遠 (2015). 高湿度中における高強度Al合金7075-T6押出材の疲労き裂伝ぱ機構. 日本機械学会論文集, 81(825), 14-00694-14-00694. https://doi.org/10.1299/transjsme.14-00694