巻号一覧
54 巻, 6 号
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研究論文
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茂泉 健, 手塚 裕康, 里 達雄2004 年 54 巻 6 号 p. 205-210
発行日: 2004年
公開日: 2007/02/20
ジャーナル フリーThe relationship between age-hardening and thermo-mechanical fatigue life was investigated for Al–Si–Mg–Cu cast alloys. The age-hardening behavior of the alloys was almost similar for the Cu-free and Cu containing alloys up to the peak aging, however, the softening behavior by over-aging was different depending on Cu contents. The behavior of decreasing in the loop-edge stress during thermo-mechanical fatigue cycles was also different depending on Cu contents. The Cu-free alloy exhibiting a long fatigue life shows significant decrease in hardness by over-aging and pronounced decrease in the loop-edge stress with increasing fatigue cycles. The Q′ or Q phase is formed in the alloys containing higher Cu contents and retards the hardness decrease during over-aging and the decrease in the loop-edge stress during the initial stage of thermo-mechanical fatigue cycles. These behaviors of the alloys containing higher Cu contents result in the decreased fatigue life. This is explained that the plastic strain localization occurs around the eutectic Si particles when the stress decrease in the initial stage of the fatigue cycles is small and causes micro cracks at around eutectic Si particles. The increase in the calculated area for an age-hardening curve is related to the increase in the fatigue life. Therefore, the thermo-mechanical fatigue life can be predicted based on the calculated area for an age-hardening curve.抄録全体を表示PDF形式でダウンロード (968K) -
川井 正彦, 山田 和広, 梅崎 智典, 小西 章, 渡辺 英雄, 美浦 康宏2004 年 54 巻 6 号 p. 211-217
発行日: 2004年
公開日: 2007/02/20
ジャーナル フリーMicrostructure of high purity Al foils as high temperature rolled and annealed for electrolytic capacitors was analyzed mainly by transmission electron microscopy. Emphasis was on the dislocation microstructure near the foil surface covered with oxide films and also on the microstructure change along the depth from the surface of the foils. The results were discussed in reference to the etching behavior of the foils. As it goes from the surface to the foil thickness of about 10 μm, dislocation structure changes from relatively random to cellular. The dislocation density and the cell-forming tendency increased with cold rolling to 50% reduction. Surface of the foils was examined by AFM to be wavy, with ridges extending parallel to the rolling marks at intervals of 2 to 4 μm. It was also revealed by TEM that band areas with high densities of dislocations and also of oxide particles extended, underneath the oxide layer, along the rolling marks. A larger number of initial-pits were formed by etching along the band areas, suggesting that the areas had acted as preferential nucleation sites for pits. By a prolonged etching, deep tunnel-pits were formed at the sites corresponding to a single dislocation or the aggregates of dislocations. Rolling the foils to 20% reduction prior to etching resulted in increased density and in decreased average size of the pits. This suggests that density of etch pits in the foils could be controlled by controlling the processing conditions before etching.抄録全体を表示PDF形式でダウンロード (3536K) -
吉原 伸二, 岡 貴志, 相浦 直2004 年 54 巻 6 号 p. 218-224
発行日: 2004年
公開日: 2007/02/20
ジャーナル フリーAxial compression and successive fracture behavior in Al–Mg–Si alloy extrusions has been investigated. Fracture after axial compression was caused by bending in macroscopic. And it was due to microcracking at the surface by tensile stress and the followed propagation in microscopic. The critical strain for cracking was corresponded with local strain in uni-axial tension. Fine graining was effective to prevent from fracture because of lowering the stress concentration value at grain boundaries. The value for 7 μm grain was a tenth of that for 130 μm. Over aging treatment was also a practical method through homogeneous deformation to lessen the effective stress at grain boundary to a fourth or a fifth of that of peak aged materials.抄録全体を表示PDF形式でダウンロード (2693K)
連載講座
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大村 悦二2004 年 54 巻 6 号 p. 225-235
発行日: 2004/06/30
公開日: 2021/06/30
ジャーナル フリーPDF形式でダウンロード (1087K)
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