鋳造工学
Online ISSN : 2185-5374
Print ISSN : 1342-0429
ISSN-L : 1342-0429
研究論文
溶体化処理後の冷却履歴がAC4CH合金鋳造材の溶質元素の存在状態に及ぼす影響
猿渡 直洋小池 純矢中山 栄浩関谷 英治
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2021 年 93 巻 6 号 p. 315-322

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  The effects of cooling profiles immediately after solution treatment on the state of solute elements in JIS AC4CH aluminum casting alloys were investigated. Three types of specimens (L.C., A.C.1, and A.C.2) with different cooling profiles in the temperature range from 560℃ to 250℃ were prepared. The L.C. specimen was cooled under a constant rate of about 6.5℃ /s. On the other hand, the A.C.1 and A.C.2 specimens were cooled with a high cooling rate in the high temperature region and a low cooling rate in the low temperature region. There were no clear differences in hardness and electrical conductivity after cooling at the indicated conditions among the three specimens. Changes in hardness and electrical conductivity during the artificial aging treatment and DSC curves suggested that the A.C.2 specimen has a larger amount of solid solution atoms than the L.C. specimen. Observation using SEM revealed that the formation of precipitates during cooling differs depending on the cooling profiles. Rod-like precipitates measuring several tens of nm in diameter and several hundreds of nm in length were observed in the second dendrite (DAII) for the A.C.2 specimen. In the primary dendrite (DAI), granular-precipitates measuring several tens of nm in diameter were observed together with the rod-like precipitates detected in the DAII. In the L.C. specimen, however, only the rod-like precipitates were observed in both the DAI and DA II. The number density of the rod-like precipitates of the L.C. specimen was smaller than that of the A.C.2. These differences in the precipitation state are thought to be due to the amount of solid solution atoms and the cooling rate in the temperature range causing the formation of each precipitate.

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