軽金属
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
45 巻, 6 号
選択された号の論文の9件中1~9を表示しています
  • 胡 健群, 熊井 真次, 関川 明功, 肥後 矢吉, 布村 成具
    1995 年 45 巻 6 号 p. 309-314
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    Effects of the volume fraction, solidification structure and particle distribution on fatigue crack growth properties in SiC particulate-reinforced cast aluminum alloy composites have been investigated. Comparing with the un-reinforced matrix alloys, fatigue crack growth resistance of the cast composites is found to be improved at the low ΔK region, deteriorated at the high ΔK region, and comparable at the Paris region. These correspond to the crack growth behaviour of the powder metallurgy-processed composites which exhibit fine matrix microstructure and homogeneous particle distribution. However, fatigue crack growth characteristics of the cast composites are influenced by the solidification structure. The dendritic solidification structure including non-uniform particle distribution results in complicated crack growth path, and such the particle segregation provides both positive and negative effects for the fatigue crack growth properties. It improves fatigue crack growth resistance at the low ΔK region due to the remarkable crack deflection and the resultant roughness-induced crack closure. While, it deteriorates the high ΔK region fatigue crack growth properties due to the enhanced monotonic fracture mode contribution.
  • 久保木 功, 本橋 嘉信, 広橋 光治
    1995 年 45 巻 6 号 p. 315-320
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    Tensile tests for the Ti-15V-3Cr-3Sn-3Al alloy with various initial structures have been carried out in a temperature range from 923K to 1098K. When the Zener-Hollomon factors (Z = ε0exp (Q/RT)) are the same, the sizes of subgrains developed by the deformation are nearly the same with each other irrespective of the initial grain sizes. When the initial grain size is almost the same with the subgrain size induced by the deformation, the maximum total elongation as large as 400% is obtained by the present study. Flow stresses depend on both the initial grain size and subgrain size. The grain size exponents (p and p') in the Dorn equation for creep are nearly 0.5, independently of the initial structures.
  • 金田 裕光, 長 隆郎
    1995 年 45 巻 6 号 p. 321-326
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    The fabrication method of particulate reinforced magnesium matrix composites using spontaneous infiltration phenomenon was developed. By pre-mixing the infiltration agent to reinforcement powder, magnesium melt infiltrated into the powder spontaneously even under pure argon gas atmosphere at 973K. In this work, fundamental experiments were carried out to find out the conditions that the spontaneous infiltration can occur in the pure Mg-SiCp system, using SiO2 powder as an infiltration agent. Microstructure observation and XRD analysis were also carried out to make clear the infiltration mechanism. The spontaneous infiltration depends both on SiCp diameter and on SiO2 content. The threshold SiO2 content decreases with increasing SiCp diameter. Microstructure observation revealed no uninfiltrated part and the formation of two kinds of reaction products. In the composites MgO, Mg2Si and no SiO2 were detected by XRD analysis. Since the reaction for producing MgO and Mg2Si from magnesium and SiO2 is exothermic (thermit reaction), it is predicted that the temperature becomes higher in the infiltration front than in other part, as temperature rise was actually confirmed during infiltration. It is predicted that the spontaneous infiltration is caused by the temperature rise due to the thermit reaction and/or the contribution of good wettability of magnesium to SiO2.
  • 池田 毅, 小松 伸也
    1995 年 45 巻 6 号 p. 327-332
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    Measurements of resistivity, density and hardness of Al-0.35mass%Zr-0.15mass%Fe-0.10mass%Si alloys for every step of Properzi continuous casting and rolling process (PCCR) have been carried out, and macrostructures of a cast bar and a wire rod have been observed. The low resistivity portion due to precipitation of alloying elements or impurities is found at the core of cast bar. Columnar structure of copper mold side in a cast bar similarly survives after rolling to 9.7mm diameter wire rod. Resistivity increment by rolling in the process is about 1.2nΩm, which should be an overestimation due to crack around intermetallic compound. At the core of rolled wire rod, hard portion is formed by some precipitation during the rolling. Filtrate analysis after hot phenol dissolution for wire rods containing 0.05-0.15mass%Si shows that Fe of 160-200ppm is in solution. Resistivity measurements for these wire rods indicates that Zr of 0.19-0.26mass% is in solution, and amount of precipitated Zr during solidification or in solid state increases with increasing amount of Si addition.
  • 藤谷 渉, 東 賢一, 古城 紀雄, 馬越 佑吉
    1995 年 45 巻 6 号 p. 333-338
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    The effect of Zr addition on superplastic deformation has been investigated using Mg-8mass%Li eutectic alloys containing 0 or 0.2mass%Zr. The (α+β) eutectic structure of these alloys was controlled to produce a fine and equiaxed grain structure by a thermomechanical treatment. Recrystallized structures were refined by the Zr addition. The elongation higher than 500% was obtained for the fine-grained specimen. These specimens showed larger values of m (-0.67), which decreased with structural changes during superplastic deformation. During the superplastic deformation, refinement of the β grains was observed, while grain growth of the α grains was found. Improvement of superplastic behavior due to the Zr addition was considered to be caused by both finer grain structure before loading and suppression of dislocation process by solute atoms of Zr, which result in both uniform deformation and dynamic recrystallization.
  • 茂木 徹一
    1995 年 45 巻 6 号 p. 339-345
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
    To investigate the grain refining mechanism of pure aluminum ingots by addition of an Al-Ti-B master alloy, unidirectional solidification and ordinary casting techniques were used. Equiaxed crystals appeared in unidirectionally solidified ingots which fluid motion did not occur during casting. It is thought that the residual TiB2 in the molten aluminum, which originated from the master alloy, acted as a nucleation site in the same manner as a peritectic reaction. An ingot consisting of only columnar structure obtained by unidirectional solidification was remelted, and then cast into a chilled mold. Each cast structure showed the equiaxed crystal zone, although no TiB2 existed in the melt. These equiaxed crystals nucleated on the mold wall and separated from the wall when the melt was cast. It is concluded that the two grain refining mechanisms during casting are important; one is due to the residual Ti compounds in the molten aluminum acting as nucleation sites, and the other is due to crystal separation from the mold wall caused by fluid motion introduced to the melt. After the Ti compounds have dissolved into the melt, only the latter mechanism may be effective.
  • 難波 明彦
    1995 年 45 巻 6 号 p. 346-354
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
  • 千葉 和郎, 当摩 建
    1995 年 45 巻 6 号 p. 355-376
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
  • 才川 清二
    1995 年 45 巻 6 号 p. 377-378
    発行日: 1995/06/30
    公開日: 2008/10/30
    ジャーナル フリー
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