鋳造工学
Online ISSN : 2185-5374
Print ISSN : 1342-0429
ISSN-L : 1342-0429
90 巻, 12 号
選択された号の論文の11件中1~11を表示しています
特集「アルミニウム合金鋳物の組織と熱処理」
解説
研究論文
  • 大杉 有沙, 數田 久生, 飯島 正彦, 趙 乙洋, 松田 健二, 池野 進, 才川 清二
    2018 年 90 巻 12 号 p. 683-690
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      Aging behavior of direct-quenched (D. Q.) and water-quenched (W. Q.) after solution treatment in Al-10%Si-0.3~1.2%Mg alloy castings were investigated by micro-vickers hardness measurement, optical microscopy and transmission electron microscopy. The hardness of D. Q. specimens were the same as W. Q. specimens, when aged temperature lowered at 373K in Al-10%Si-0.3Mg, Al-10%Si-0.6Mg alloy and at 398K in Al-10%Si-1.2Mg alloy, respectively. When aging temperature was over 398K, the peak-hardness of W. Q. specimens was higher than that of D. Q. specimens in the Al-10%Si-0.3Mg and Al-10%Si-0.6Mg alloys. On the other hand, when the aging temperature was over 423K, the peak-hardness of W. Q. specimens was higher than that of D. Q. specimens in the Al-10%Si-1.2Mg alloy. The reason of those tendency contributes to the difference between clusters and G. P zone in the α-matrix.

  • 趙 乙洋, 數田 久生, 大杉 有沙, 飯島 正彦, 池谷 拓哉, 松田 健二, 池野 進, 才川 清二
    2018 年 90 巻 12 号 p. 691-696
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      Aging behavior of step castings at different cooling rates in Al-10%Si-0.3%Mg alloy were investigated by micro-vickers hardness measurement, optical, scanning electron and transmission electron microscopy. The hardness of as-cast states increased with increasing cooling rate. Despite the difference in hardness before artificial aging in as-cast states, the hardness in artificial aging curves was varied with aging time. The difference in hardness between fat and thick portions was due to refining eutectic Si phase with increasing cooling rate. There was no precipitation in any wall thickness in the as-cast castings. On the other hand, in peak-aged specimens obtained from castings with 15mm thick walls, which consists of two regions, one is the domain of coarse precipitation and the other one is fine precipitation. The rod-like and granular precipitates were observed in peak-aged specimens obtained from castings with 1mm thick walls.

  • 董 樹新, 岩田 靖, 八百川 盾, 日比 加瑞馬, 大石 敬一郎
    2018 年 90 巻 12 号 p. 697-702
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      The growth of aluminum alloy die castings can be eliminated with a suitable heat treatment. To elucidate the parameters affecting heat treatment conditions, we investigated the effects of alloying elements on the precipitation behavior of supersaturated silicon in die castings during heat treatment using JIS ADC12 alloy (hereafter referred to as ADC12) and Al-11%Si alloy, considering that the former contains several alloying elements while the later no other elements except for silicon.

      Most of the supersaturated silicon in ADC12 alloy die castings precipitated with a short time of heat treatment, resulting in a large number of fine silicon precipitates dispersed in the primary aluminum phase. However, the supersaturated silicon in Al-11%Si alloy die castings needed a long time of heat treatment to precipitate and resulted in fewer and larger silicon precipitates in the primary aluminum phase than that of ADC12 alloy die castings. The concentration of magnesium, copper and silicon etc. was analysed in the silicon particle near the interface with aluminum matrix in ADC12 alloy die castings using a three dimensional atom probe. These alloying elements of magnesium, copper, etc. are considered to have formed clusters suitable as the nucleuses of silicon precipitation during die casting or at the early stage of heat treatment thus promoting the precipitation of the supersaturated silicon during heat treatment.

      To confirm this assumption, we examined the growth behavior of the die castings of Al-11%Si alloy with an addition of magnesium. The growth of the die castings with magnesium addition were faster than that of Al-11%Si alloy die castings during heat treatment, and the promoting effect of magnesium was verified on the precipitation of the supersaturated silicon in ADC12 alloy die castings. Therefore, the presence and the content of alloying elements such as magnesium, copper, etc. should be considered when deciding the heat treatment conditions for removing the growth of the die castings of Al-Si system alloys.

  • 鈴木 大介, 中山 栄浩, 八代 浩二, 星野 昌子
    2018 年 90 巻 12 号 p. 703-709
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      In a previous article, rapid solution treatment until five minutes with the temperature rising rate of 50℃/sec using high frequency induction heating was applied to JIS ADC12 high pressure die castings. This heat treatment leads to the moderate increase in solid solution amount, preventing pores, and eutectic silicon refining, and spheroidizing. Especially, changing the eutectic silicon shape improves fracture toughness. In this article, the effect of rapid solution treatment on toughness improvement was evaluated from tensile strength and ductility. The results were as follows. It was found that elongation to fracture increased about 67% by solution treatment, moreover tensile strength increased by around 10% with aging treatment for four hours at 200℃, compared with as-cast specimens. Under-aging treatment was more effective than peak aging for toughness improvement in rapid solution treatment. The one hour aging treatment resulted in about 20% increase in elongation to fracture, while significant decrease was not found in tensile strength, in comparison to specimens treated by peak aging (200℃, 4hrs). In addition, it was assumed that the microstructure of as-cast specimens contained considerable solid solution amounts due to rapid cooling of castings, and also included fine precipitation formed during natural aging for a long-term period.

  • 猿渡 直洋, 中山 栄浩
    2018 年 90 巻 12 号 p. 710-718
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      The effect of eutectic Si particles distributions on ductility in JIS AC4CH aluminum casting alloy (referred to as AC4CH alloy) was investigated through experimental approaches. AC4CH alloys were subject to ECAP processing at the 2nd, 4th, 6th, and 8th - passes to prepare samples with various distributions of eutectic Si particles. First, a method for the quantitative evaluation of the distribution of the eutectic Si particles using an area grid was examined. The eutectic Si particle distributions were quantified for each plane in the test pieces for unprocessed and ECAP processed samples. These quantitative values corresponded with the eutectic Si particle distributions visually observed on the microstructural images. The relationship between the quantified values of eutectic Si particle distributions and the elongations obtained by the tensile test were investigated. The uniform, local, and fracture elongations determined by the tensile test were found to increase as the number of ECAP passes increased. After the 8th - pass ECAP processing, elongation increased by 49%, 64%, and 54%, respectively in each of these types, compared to the unprocessed samples. Correlation was found between the mean quantified values of eutectic Si particle distribution and elongations. The experiments confirmed that the homogenization of the three-dimensional distribution of eutectic Si particles leads to increasing elongation.

技術報告
技術論文
  • 青山 俊三, 大森 将尚, 上坂 直人, 岩田 靖, 小林 正和, 新川 真人
    2018 年 90 巻 12 号 p. 730-736
    発行日: 2018/12/25
    公開日: 2019/01/01
    ジャーナル フリー

      The measurement of the residual stress in aluminum alloy die castings by x-ray method was investigated in order to apply this method for improving the analysis accuracy of the deformation of aluminum alloy die castings. The residual stress of one flat type experimental die castings and six kinds of practical die cast products were assessed by the x-ray method. As a result, the stress occurring in a deformed die castings was found to be measurable by the x-ray method. However, the residual stress in the as-cast die castings measured by the x-ray method showed a lower compressive value than that measured by the stress relaxation method in which the die castings was cut off and the residual stress was measured by strain gauges. The cause of the inconsistency between the x-ray method and stress relaxation method was estimated as the decrease in the lattice constants of aluminum measured by x-ray due to the solid solution of silicon and copper in aluminum. Therefore, the x-ray method can be used to measure the residual stress in die castings after being calibrated by the stress relaxation method. The residual stress on the surface of the die castings was found to become tensile stresses after heat treatment at 200℃ or 250℃.

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