日本金属学会誌
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
早期公開論文
早期公開論文の8件中1~8を表示しています
  • 柴本 宏, 木村 晃彦, 長谷川 雅幸, 松井 秀樹
    原稿種別: 論文
    論文ID: J2019004
    発行日: 2019年
    [早期公開] 公開日: 2019/11/15
    ジャーナル フリー 早期公開

    Micro-Vickers hardness and positron lifetime were measured after 1 MeV proton irradiation to a fluence of 3 × 1017 ions/cm2 at below 80℃ and post-irradiation isochronal annealing to 650℃ to investigate the effects of nickel (Ni), phosphorous (P) and sulfur (S) on the irradiation hardening of Fe-0.2 mass% C-0.3 mass% Cu model alloy. With increasing the Ni content to 0.6 mass%, irradiation hardening was increased, while a further increase to 1 mass% resulted in a small reduction. The addition of 0.05 mass% P increased the irradiation hardening of the model alloys irrespective of the addition of 0.6 mass% Ni, while the addition of 0.05 mass% S showed almost no effect on the hardening. Positron lifetime measurements revealed that the intensity of long-lifetime component, namely the number density of microvoids, increased and decreased for the alloy added with P and S, respectively. However, no significant effect of Ni content on the long-lifetime component was observed. Post-irradiation anneal-hardening was large and became a maximum at around 350-375℃ in most of the alloys studied. The addition of 0.6 mass% Ni caused almost no effect on the annealing behavior, while further addition of 0.05 mass% P reduced the hardness change by the annealing to 400℃. During post-irradiation annealing to around 400℃, the long-lifetime component increased in the alloy with P, but it was so small in the alloy with S or manganese (Mn). These suggest that P enhances the growth of the microvoids but S as well as Mn suppress it.

     

    Mater. Trans. 60(2019) 93-98に掲載

    Fig. 4 Annealing behavior of ΔHV of each alloy where the ΔHV is estimated to be a subtraction of the hardness of unirradiated alloy after a given annealing from the hardness of the post-irradiation annealed alloy:(a) Fe-C-Cu alloy and (b) Fe-C-Cu-Ni alloy. Fullsize Image
  • 市川 裕士, 所 竜太郎, 亀山 雄高
    原稿種別: 論文
    論文ID: J2019033
    発行日: 2019年
    [早期公開] 公開日: 2019/11/15
    ジャーナル フリー 早期公開

    Fine particle peening (FPP) is a surface modification process in which fine hard metallic particles project onto the substrate. During this process, shot particles that remain transfer to the substrate and form a complex and multi-layered lamellar structure in which transferred fragments are distributed in the depth direction and several tens of micrometers from the surface. Because the bond strength at each interface of this structure and its generation mechanism are unclear, the local bond strength of the laminated interface was evaluated in this study by a microscale tensile test conducted by focus ion beam facilities. In the transferred lamellar modified region, the hardness was considerably higher than that of as-received materials, and the microscopic bonding strength between the transferred copper or iron and the aluminum matrix was 300 MPa or greater. When steel particles were used with FPP, iron oxide was mainly transferred to the aluminum matrix. However, copper plating on the particles suppressed the oxidation of the steel composing the particles and, as a result, the metallic steel was transferred. The bonding strength was improved by oxidation-controlled steel particles.

    Graphical Abstract Fullsize Image
  • 山口 義矢, 阿部 真弓, 田島 遼太郎, 寺田 芳弘
    原稿種別: 論文
    論文ID: J2019032
    発行日: 2019年
    [早期公開] 公開日: 2019/11/05
    ジャーナル フリー 早期公開

    The evolution of microstructure during the isothermal aging at 1173 K was investigated for the wrought Ni-based superalloy Udimet 520 solution-treated at 1393 K for 4 h followed by various cooling rates. The age-hardening behavior was observed during the isothermal aging for the water-quenched (WQ) and air-cooled (AC) specimens after the solution treatment, while it could not be detected for the furnace-cooled (FC) specimen. No primary γ′ particles were observed in any continuously cooled samples. For the WQ and AC specimens, the size of the secondary γ′ precipitates increased during the isothermal aging along the Ostwald ripening and their morphology evolved from a spherical shape to an intermediate shape between spherical and cuboidal ones. On the contrary, the secondary γ′ particles exhibited an octodendritic shape for the as FC specimen, and the octodendritic character of the secondary γ′ particles was emphasized during the isothermal aging resulting in the splitting of the secondary γ′ particles. It was found that the splitting of γ′ particles occurs during the isothermal aging for the Alloy 80A with a lower volume fraction of γ′ phase around 20%.

    Fig. 8 FE-SEM images of Udimet 520 solution-treated at 1393 K/4 h/FC followed by the aging treatment at 1173 K/1 h (a), 10 h (b), 100 h (c) and 1000 h (d). Fullsize Image
  • 下川 智嗣, 安井 紀一朗, 新山 友暁, 木下 惠介, 澤田 英明
    原稿種別: 論文
    論文ID: J2019036
    発行日: 2019年
    [早期公開] 公開日: 2019/11/05
    ジャーナル フリー 早期公開

    To investigate the reason why low-carbon steels with carbon-clusters shows the maximum strength during low-temperature aging, interactions between an edge dislocation and carbon clusters are performed through molecular dynamics (MD) simulations. Carbon clusters are modeled based on atom probe tomography (APT) observations. To express a transition process of carbon configurations from solid solution state to carbon cluster state to precipitation state during aging process, we reduce a carbon presence area with a fixed number of carbon atoms, i.e., the carbon concentration can be continuously increased. The MD simulations can represent the age hardening/softening tendency observed in the experiment and the carbon cluster state shows the maximum strength where the dislocation passes through the carbon cluster not by the Orowan but by the cutting mechanism. The MD analysis found that partial clusters in the carbon cluster act as the main resistance to dislocation passage; the biased distribution of carbon atoms is also confirmed in the actual observed carbon clusters by APT. A new interaction mechanism between dislocation and carbon clusters is developed based on the phenomena in the MD simulations and the availability is discussed.

    Fig. 11 Prediction of critical shear stresses for dislocation to pass through carbon clusters with different diameters by three types of dislocation-carbon cluster interaction mechanisms. Fullsize Image
  • 奥山 哲也, 東園 拓海, ゴ フィン キン ルアン, 工藤 昌輝
    原稿種別: 論文
    論文ID: J2019029
    発行日: 2019年
    [早期公開] 公開日: 2019/10/28
    ジャーナル フリー 早期公開

    The effect of Nb on microstructure and thermal-shock resistance was investigated for as cast and annealed JIS SCH21 steels. Primary NbC carbide were crystallized together with M23C6 at grain boundary in as cast steel. Decomposition of primary M23C6 was detected, while NbC was also hardly decomposed when annealed at elevated temperature. It was found that chromium carbides had low thermal stability but primary NbC carbides played a role in preventing propagation of micro-cracks and restraining shape deformation under condition both heating and quenching. As a result, thermal-shock resistance was improved in the Nb-added steel.

    Fig. 12 Partitioning of alloying elements analyzed by STEM-EDS for micro-crack in Nb steel occurred when thermal shocked at 1223 K for 300 cycles. Fullsize Image
  • 中田 伸生
    原稿種別: オーバービュー
    論文ID: J2019030
    発行日: 2019年
    [早期公開] 公開日: 2019/10/21
    ジャーナル フリー 早期公開

    Martensitic reversion from bcc-martensite to fcc-austenite is an important phase transformation to improve mechanical properties of steels remarkably as well as other phase transformations. However, few studies have undertaken to investigate the martensitic reversion, because it hardly occurs in carbon steels. In the present overview, some characteristics of the martensitic reversion were explained briefly with reference to the previous studies, and a couple of applications of microstructural control for high alloy steels using the martensitic reversion were introduced. Furthermore, a novel heat treatment through the martensitic reversion to improve strength and toughness of low alloy martensitic steel was proposed.

    Fig. 7 EBSD data, (a-d) inverse pole figure, (e) phase and (f-h) kernel average misorientation maps, showing recrystallization of martensitic reversed austenite by bulge mechanism in Fe-32%Ni-5%Co cast alloy, which were after (a, e) sub-zero treatment at 77 K and annealing at (b, f) 923, (c, g) 1073 and (d, h) 1173 K. Fullsize Image
  • 堀川 敬太郎, 小林 秀敏
    原稿種別: 論文
    論文ID: JB201903
    発行日: 2019年
    [早期公開] 公開日: 2019/10/21
    ジャーナル フリー 早期公開

    In the present study, a new method for hydrogen charging in aluminum was developed which named friction in water (FW) process. The hydrogen charging was carried out by polishing aluminum surfaces for 1 h with a silicon carbide emery paper in water at room temperature. For comparison, hydrogen-uncharged specimens were also prepared. The total amount of hydrogen in aluminum clearly increased after the FW process, during which hydrogen was generated by the chemical reaction between water and the non-oxide coated aluminum. After hydrogen charging by the FW process, aluminum showed a decrease in ductility in conventional strain rate tensile testing. Hydrogen microprint technique (HMT) revealed that hydrogen atoms absorbed by the FW process was diffused to the opposite surface in the thickness direction.

    Fig. 3 Schematic of the connection of sensor gas chromatography and the reaction container. Fullsize Image
  • 渡邉 桃加, 北原 弘基, 高松 洋平, 津志田 雅之, 安藤 新二
    原稿種別: 論文
    論文ID: J2019034
    発行日: 2019年
    [早期公開] 公開日: 2019/10/11
    ジャーナル フリー 早期公開

    Pure Mg, Mg-0.5 at%Al, Mg-0.5 at%Zn, Mg-0.5 at%Y, Mg-0.9 at%Y, and pure Zn single crystals were applied to indentation tests using a spherical indenter to allow experimental investigation the roles both slips and twinning induce on the formation of indentation. When indented on (0001), all single crystals displayed indentation of circular morphology without slip lines and twins. Mg and Mg alloys' indentation sizes were found dependent on critical resolved shear stress (CRSS) for basal slip in (0001) indentations. Zn (0001) indentation size depends on CRSS for both basal and pyramidal slips. Conversely, when indented on (1010) and (1210), all single crystals had indentations elongated to [0001] with basal slip lines around indentations. Also, {1012} twins were observed in Mg-0.5 at%Al and Mg-0.5 at%Zn but were scarce in Mg-Y. Pure Zn displayed second order pyramidal slips. Sizes of both (1010) and (1210) indentations were found dependent on CRSS for basal slips and for {1012} twins.

    Fig. 3 Optical micrographs of indentations on (1-210) in (a) Mg, (b) 05Al, (c) 05Zn, (d) 05Y, (e) 09Y and (f) Zn single crystals when indented at 4.90 N. Fullsize Image
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