Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
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Regular Article
  • Hiroshi Shibamoto, Akihiko Kimura, Masayuki Hasegawa, Hideki Matsui
    Type: Regular Article
    2020 Volume 84 Issue 2 Pages 37-43
    Published: February 01, 2020
    Released: January 25, 2020
    [Advance publication] Released: November 15, 2019
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    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.

    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
  • Keisuke Takemoto, Hiroaki Rikihisa, Masayuki Tsushida, Hiromoto Kitaha ...
    Type: Regular Article
    2020 Volume 84 Issue 2 Pages 44-49
    Published: February 01, 2020
    Released: January 25, 2020
    [Advance publication] Released: December 13, 2019
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    Tensile tests were applied to rolled Mg-Y alloy sheets with various contents of yttrium to investigate effects of yttrium addition on activities of basal slip and non-basal slip systems so as to clarify the relationship between tensile properties and activities of slip systems. 0.2% proof stress of Mg-Y alloys increased with increasing yttrium content ranging from 0.5 to 1.2 at%. Ductility increased with increasing yttrium content no more than 0.9 at% but decreased when 1.2 at% was added. Frequencies of basal and non-basal slips increased by yttrium addition. The frequency of {1011}<1123> first order pyramidal slip (FPCS) increased with increasing yttrium content no more than 0.9 at% and decreased when 1.2 at% was added. With increasing yttrium content, the frequency of {1122}<1123> second order pyramidal slip (SPCS) decreased, while that of {1010}<1120> prismatic slip (PS) increased. The highest total frequency of non-basal slips was observed in Mg-0.9Y, showing the highest ductility. Enhancement of ductility on magnesium was caused by activation of both basal and non-basal slips through yttrium addition.

    Fig. 5 Optical micrographs of slip lines in 0.5Y-1 (ε = (a)1.7% and (b)5.5%) and 1.2Y-2 (ε = (c)2.0% and (d)5.2%). Slip lines were identified to be BS, PS, FPCS and SPCS using the trace analysis. I and II indicate connecting points of BS and FPCS, and BS and SPCS, respectively. Fullsize Image
  • Daiki Ueda, Satoshi Oue, Tomio Takasu, Hiroaki Nakano
    Type: Regular Article
    2020 Volume 84 Issue 2 Pages 50-57
    Published: February 01, 2020
    Released: January 25, 2020
    [Advance publication] Released: December 06, 2019
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    Electrodeposition of Zn–Zr oxide and Zn–V oxide composites was performed under galvanostatic conditions from an unagitated sulfate solution containing Zn2+, Zr4+, or VO2+ ions and an additive such as polyethylene glycol (PEG). The sulfate solution had a pH of 2 and the electrodeposition was performed at 313 K. The effects of PEG on the co-deposition of the Zr oxides and V oxides and their polarization behavior were investigated. Additionally, the effects of PEG on the microstructure of the deposits were investigated. Although the Zr content in the deposits obtained from the Zn–Zr solution without PEG was approximately zero, it increased significantly at a current density above 1000 A m−2 following the addition of PEG. In the Zn–V solution, the V content in the deposits obtained from 100 A m−2 to 2000 A m−2 was higher with PEG than that without PEG. In the presence of PEG, the cathode potential polarized, the rate of hydrogen evolution increased, and the hydrolysis reaction of Zr4+ and VO2+ ions occurred easily. This resulted in the Zr content and V content increasing in the deposits. Additionally, the crystal platelets of Zn in the Zn–Zr oxide film and the Zn–V oxide film became fine, and the surface coverage of the spongiform Zr oxide and the film-like V oxide increased. Furthermore, the corrosion current densities of the Zn–Zr oxide film and the Zn–V oxide film obtained from the solution with PEG were lower than those from the solution without PEG. The reduction reaction of dissolved oxygen decreased in the films with PEG, thereby decreasing the corrosion current density.

    Fig. 1 Zr and V content in deposits obtained at various current densities in (a)Zn-Zr and (b)Zn-V solutions with and without PEG [◯ Without PEG, ● With PEG]. Fullsize Image
  • Keita Uchida, Satoshi Oue, Hiroaki Nakano
    Type: Regular Article
    2020 Volume 84 Issue 2 Pages 58-65
    Published: February 01, 2020
    Released: January 25, 2020
    [Advance publication] Released: December 27, 2019
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    To elucidate the effects of polyethylene glycol (PEG) and glue on the deposition behavior of Zn from electrowinning solutions and its crystal structure, Zn electrodeposition was performed at a current density of 600 A·m−2 and a charge of 8.64 × 106 C·m−2 in an agitated sulfate solution containing 1.07 mol·dm−3 and 1.8 mol·dm−3 of ZnSO4 and H2SO4, respectively, at a temperature of 45℃. With the additions of PEG and glue, the evolution of hydrogen was suppressed at current density region less than the critical current density for Zn deposition, resulting in decrease in critical current density of Zn. The degree of decrease in critical current density of Zn was larger with glue than that with PEG. The current efficiency for Zn deposition was higher with PEG and glue than that without at low current density region because the critical current density of Zn decreased with additives. Since the additives suppressed Zn deposition more than the hydrogen evolution at high current density region, the current efficiency of Zn decreased with increasing concentration of additives in solution. At high current density region, there was little difference in current efficiency of Zn between PEG and glue. The effect of molecular weight of PEG on the current efficiency of Zn was rarely observed at molecular weight above 2000. With an addition of PEG, the deposits became fine platelets crystals with preferred orientation of {1011} and layered pyramidally, while the deposits orientated to {1120} preferentially and the platelets crystals grew perpendicularly to the substrate with an addition of glue. The surface roughness of deposited Zn decreased with additives and it was smaller with PEG than that with glue.

    Fig. 4 Current efficiency for Zn deposition in the solutions containing glue and various molecular weights of PEG (● additive-free, ▲ Glue 6000, ○ PEG 200, △ PEG 2000, □ PEG 6000, ◇ PEG 35000, Concentration of additives : 10 mg・dm−3). Fullsize Image
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