Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 36, Issue 8
Displaying 1-16 of 16 articles from this issue
  • Masaaki Tokunaga
    1989 Volume 36 Issue 8 Pages 877-884
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Over-quenched Nd-Fe-B flakes for isotropic bonded magnets show high coercivity (iHc) by post-heat treatment. This flake has the lowest temperature coefficient of iHc around -0.45/°C and the smallest grain size in the Nd-Fe-B materials. Enough thermal stability and magnetizability are obtained for isotropic bonded magnets with these characteristics of the flake. The Nd14Fe80B6 ternary composition has the best hot workability (die upsetting) from stress-strain curves for the initial stage of die upsetting at hot working temperatures. Alignment of c-axis along die upsetting direction is obtained, but decrease in iHc due to grain coarsening is resulted. Ga is the best for enhancing iHc without deterioration in hot workability. Typical magnetic properties of Nd14Fe79.25B6Ga0.75 die-upset magnets are (BH)max=36 MGOe and iHc=19 kOe. The iHc of powders made by pulverizing the die-upset magnet is nearly independent of particle size. Anisotropic bonded magnets are developed using this powder. Typical magnetic properties of Nd-Fe-B-Ga compression moulded magnets are (BH)max=15 MGOe and iHc=19 kOe.
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  • Hitoshi Hashimoto, Saburo Yashima
    1989 Volume 36 Issue 8 Pages 885-889
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    Selection function and breakage distribution function of a tumbling ball mill were derived theoretically by measuring the impact force of balls on the mill shell and by considering the fracture properties of powder particles under compressive impact force. As a result, conversion ratio of the input energy into the impact energy of balls on the shell was found to be very low and the derived functions disagreed with the measured ones. From these results, grinding process of the tumbling mill was presumed to consist of fracture process of the powder particles under the compressive impact force and frictional crushing process under the shear force.
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  • Tamotsu Ueyama, Takashi Yamamoto, Kiyoshi Okazaki
    1989 Volume 36 Issue 8 Pages 890-897
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    The relations among packing density in Al2O3 green sheet and shrinkage, demensional stability and warping were discussed theoretically and experimentally. Dimensional stability in Al2O3 substrate strongly depended on packing density of particles in the green sheet and was experimentally varied by 0.5% when the packing density was changed around 1 vol%. These experimental values were fairly agreed with those obtained by theoretical considerations. Moreover, it was found that the warping observed in the sintered substrate was caused by the difference of shrinkage in thickness direction, which was due to the variations of packing density and binder content in thickness direction. This variation could be controlled around zero using the green sheet with a packing density of above 60 vol%. We could get the Al2O3 substrate with high dimensional stability.
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  • Yasuhiko Hashimoto, Koichiro Koyama, Kenji Suzuki, Teruo Takahashi
    1989 Volume 36 Issue 8 Pages 898-902
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Two new carbide phases, M1-phase and M2-phase, were found in the Ni-Ti-Mo-C quaternary system at 1273 K. M1-phase with the composition (Ti0.46Mo0.54)C is hexagonal with a=0.60313 run, c= 1.02371 nm. M2-phase with the composition (Ti0.28Mo0.72)C is orthorhombic with a=0.51610 nm, b=1.58280 nm, c=0.29810 nm. The Ni content in the both compounds was less than 0.1 at %. Phase relationships among such phases as [γ+C+δ+M1], [γ+C+M1+M2], [γ+C+M2+α-MoC1-x], [γ+δ+ M1+M2], [γ+δ+M2+α-MoC1-x] were also established.
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  • Yuji Katsumura, Kaoru Sobata, Yoshito Uehara, Hisashi Suzuki
    1989 Volume 36 Issue 8 Pages 903-907
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    Three sorts of Al2O3-25 vol% TiC ceramics having different grain sizes were prepared by hot-pressing and cutting performance of the ceramics tools was studied as a function of Al2O3 grain size. The results obtained were briefly summarized as follows; The fine grained tools showed the largest flank wear (VB) in turning test of grey cast iron, but on the other hand, they showed the smallest VB in the test of alloyed tool steel. The coarse grained tools often exhibited a shorten life time due to flaking.
    Discussion on the VB which had a reverse tendency in relation to the sorts of works and flaking mechanism was finely given.
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  • Shigeya Sakaguchi, Shuichi Imasato, Hiroshi Ito, Ryozo Nakamura
    1989 Volume 36 Issue 8 Pages 908-912
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    A high chromium cast iron (Fe-27Cr-3.1C) was applied to a binder of WC base cemented carbide because of its superior wear, corrosion and oxidation resistances, and some properties of the sintered WC-(Fe-Cr-C) alloys were investigated.
    The results of this work are summarized as follows:
    (1) The uniform and hard alloys were obtained by means of conventional vacuum sintering process, and these alloys were composed of WC, α-Fe and (Fe-Cr)7C3 phases.
    (2) The hardness of this alloy was higher than that of WC-Co alloy, and highest Vicker's hardness of 2000 could be achieved.
    (3) Wear resistance of this alloy was better than that of WC-Co alloy.
    (4) Except in 10% HNO3, corrosion resistance of this alloy against some acids was similar to that of WC-Co alloy.
    (5) Oxidation resistance of this alloy at high temperature was better than that of WC-Co alloy and was the same as that of TiC-TiN cermet.
    These improved properties of this alloy will be mainly caused by a (Fe-Cr)7C3 phase dispersed in the binder of this alloy.
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  • Nobujiro Tsuchiya, Masahide Fukuda, Tsuyoshi Nakai, Hisashi Suzuki
    1989 Volume 36 Issue 8 Pages 913-916
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    It was previously reported by the present authors that flaky structures consisting of βt often appeared and acted as fracture sources in WC-βt-Co alloy, the structures being caused by the agglomerated flaky powder formed during ball-milling. The mechanism why the flaky structures developed during sintering was studied. It was suggested that the flaky structures were formed, as the result of different kinds of massflows such as liquid flow, and solution and precipitation of WC and βt particles, taking place in or near the region of flaky powder during sintering.
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  • Kazuhiko Majima
    1989 Volume 36 Issue 8 Pages 917-925
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    The effect of eutectoid β stabilizing elements on the sintering characteristics of Ti powder compacts was carried out in order to get the high dense sintered Ti alloy by conventional sintering method through blended elemental process.
    The addition of Fe, Ni and Co among eutectoid β stabilizing elements showed the excellent effect on the densification of Ti powder compacts, where the sintered density ratio of Ti-4 mass%Co specimen was higher than 99%, and both of their ratios of Ti-4 mass%Fe and Ti-4 mass%Ni were higher than 98%. The tensile properties for sintered Ti-4 mass% Co and Ti-4 Fe specimens were remarkably improved by (α+β)-quenching after β-solution treatment, and the corrossion resistance of Ti-4 mass%Fe specimen in both of physiological saline solution and 1N-HCl solution was confirmed to be better than those of Ti-6 Al-4 V specimen or Ti-5 Al-2.5 Fe specimen which was newly developed as implanted material. In addition, the implantation test maintained in the tibia of rabbit for 14 months showed that Ti-4 Fe specimen had the excellent biocompatibility.
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  • Koichiro Koyama, Yasuhiko Hashimoto, Kenji Suzuki, Hideki Matsuo
    1989 Volume 36 Issue 8 Pages 926-932
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The standard Gibbs free energy of formation of NiW2B2 was determined in the temperature range from 1273 K to 1423 K by measuring electromotive forces of a galvanic cell having a solid oxide electrolyte. Also, the standard Gibbs free energies of formation of WO2 and WO49/18 and the Gibbs free energy of mixing of the Ni-W binary system, which were necessary to determine the standard Gibbs free energy of formation of NiW2B2, were determined. The results obtained are as follows:
    (1) ΔG°f(NiW2B2)=-199000+3.08T±1000J/mol (1273-1423 K).
    (2) ΔG°f(WO2)=-573100+167.0T±100J/mol (1223-1473 K).
    (3) ΔG°f(WO49/18)=-755400+213.2 T+200J/mol (1223-1423 K).
    (4) The Gibbs free energy of mixing of the Ni-W solid solution (Ni-16.4 mol%W), which is in equilibrium with NiW2B2, is:
    ΔGm(Ni-16.4 mol%W)=-4040+0.280T±3J/mol (1273-1423 K).
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  • Masaru Yokota, Akira Takase, Hiroshi Nagai, Keiichiro Shoji
    1989 Volume 36 Issue 8 Pages 933-938
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    Damping characteristics of sintered Fe-0.030 mass%C and Fe-0.014%C-2%Sn compacts which were infiltrated with pure Pb or Pb-2%Sn were investigated by using the magnetic driving resonant vibrating method. The purpose of C and Sn additions to Fe base skeletons was in improving the strengthening of skeletons, and Sn addition to Pb was in improving the wettability of infiltrants to Fe base skeletons. Infiltrated compacts were produced by sintering at 1273 K for 7.2 ks and then infiltrating at 1123 K for 600 s in purified H2 atmosphere.
    Results obtained were summarized as follows:
    (1) The ratio of infiltration (volume of infiltrants/total volume of porosity in the skeleton) for Fe-C-2%Sn compacts was a little inferior to that for Fe-C compacts, because of the formation of closed pores by melting out of Sn.
    (2) Typical Snoek peaks were observed for Fe-0.030%C/Pb (A/B: A; skeleton, B; infiltrant) and for Fe- 0.030%C/Pb-2%Sn compacts in the temperature dependent internal friction (Q-1) curves. Sn addition to Fe base skeletons markedly enhanced the value of Q-1 at the temperature of the appearance of Snoek peak, o.iginating in the relaxation of grain boundary diffusion of Sn. Sn addition to Pb infiltrant generally tended to lower the value of Q-1.
    (3) Q-1 for Fe-0.030%C/Pb or /Pb-2%Sn at 433 K appearing Snoek peak did not show the strain amplitude dependency up to εmax=5-8×10-8, and over that, increased with the increase of εmax- On the other hand, Q-1 for Fe-0.014%C-2%Sn/Pb or /Pb-2%Sn did not show the strain amplitude dependency up to smax??1×10-5. Q-1 of all specimens described above at room temperature showed the strain amplitude dependency above εmax??1×10-5.
    (4) Damping index of Fe-0.030%C/Pb or /Pb-2%Sn was about 9%, rather higher than that of Fe-0.014%C-2%Sn/Pb or /Pb-2%Sn. On the other hand, mechanical properties such as tensile strength and hardness of Fe-0.014%C-2%Sn/Pb or /Pb-2%Sn was inversely a little higher than that of Fe-0.030%C/Pb or /Pb-2%Sn.
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  • Yoshikazu Suzuki, Teruhisa Watanabe, Shigeo Tsuchida
    1989 Volume 36 Issue 8 Pages 939-944
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    The rolled sheets were made by P/M method from 7091 alloy powder, and effects of degassing conditions on mechanical properties and microstructures were studied. The green compacts of the powder were encapsulated, and degassed at 653 K-773 K for 0.3 h-24 h in about 10-3 Pa vacuum. Following degassing, the compacts were hot pressed, hot rolled with 88% reduction, and then cold rolled with 67% reduction to obtain 1 mm thick sheets. Results obtained were as follows:
    1) The degassing conditions considerably influenced the ultimate tensile strength (UTS) and the yield strength (YS) of the P/M sheets in T6 temper. The P/M sheets made through degassing at 733773 K for I h or more showed the highest UTS of about 630 PMa.
    2) The recrystallized grain size of the P/M sheets in T6 temper was also influenced by the degassing conditions, and the relatively high degassing temperatures of 733-773 K led to fine grain size.
    3) The P/M 7091 alloy sheets made through degassing at 733 k for 1 h showed higher UTS than those of I/M 7091 and I/M 7075 alloy sheets in T6 temper, and the differences were 35 MPa or more.
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  • Yoshikazu Suzuki, Teruhisa Watanabe, Shigeo Tsuchida
    1989 Volume 36 Issue 8 Pages 945-949
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    Effects of degassing conditions on hydrogen content and other properties of a P/M 7091 alloy were studied. The green compacts of the alloy powder were encapsulated and vacuum-degassed with various conditions, and then hot pressed and rolled. The degassing conditions were changed within 653-793 K in temperature, 0.3-24 h in time, 2.1-2.4 g/cm3 in green density and 100-10-5 Pa in degree of vacuum. Results obtained were as follows:
    1) The hydrogen content of 7091 alloy powder was about 55 p.p.m. And that of a P/M billet made from 7091 alloy powder without vacuum-degassing was close to 40 p.p.m.. Therefore the billet included a number of residual pores at the boundaries between powder particles.
    2) Hydrogen contents of the hot pressed P/M billets and rolled P/M sheets decreased with increasing the degassing temperature and the time. The P/M materials made through degassing at 653 K for I h contained about 5 p.p.m. hydrogen, and through degassing at 773 K for I h and for 24 h, contained about 1.2 p.p.m., 0.6 p.p.m. respectively. The P/M sheets were pore free even when they had high hydrogen content about 5 p.p.m.. Hydrogen contents of the P/M 7091 alloy sheets were in 0.6-5 p.p.m., which were higher than that of a I/M 7075 alloy sheet of 0.11 p.p.m..
    3) Effects of both the green density and the degree of vacuum at degassing on the hydrogen content of the P/M billets were little, excepting the fact that the higher green density of 2.4 g/cm3 resulted in slightly high hydrogen content.
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  • Shinji Yamada, Akira Sugafuji, Tetsuya Matsuda, Yasuhiro Shirasaka, To ...
    1989 Volume 36 Issue 8 Pages 950-956
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    In order to evaluate the joining between steels and the powder rolling sheets, the bonding conditions considering the role of the porosity, were investigated as functions of sintering temperature, sintering time and bonding pressure under the condition of dissociated ammonia gas atmosphere. Results obtained were as follows:
    (1) As a constant sintering time, the tensile strength of the joints increased at elevated bonding pressure. However, no particular change was recognized for the hardness of crystalline in the matrix phase.
    (2) The growth of crystallines and the increasing of pores between graphite and matrix phase were restrained with increasing the bonding pressure.
    (3) During tensile test, the specimens were broken outside the joint area in cases of sintering temperatures of 1150 K, 1200 K and 1250 K at the bonding pressure of 0.15 MPa. The increase of temperature and time during the sintering reduced porosities in the contact area, and in addition, the extension of diffusion layers were observed by EPMA.
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  • Shigenori Tanabe, Jiro Shibata, Hiroyuki Ichinose
    1989 Volume 36 Issue 8 Pages 957-962
    Published: December 25, 1989
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    In order to examine sintering behavior in a and γ phases of iron based mixed powder compacts, sintering process of iron and wolfram mixed powders was studied, and sintering rate of iron-wolfram and iron-nickel alloys were further studied quantitatively by measurements of neck growth between their wires. The results were summarized as follows:
    (1) Neck growth rate of iron-wolfram alloy wires was remarkably larger in a phase than in γ phase, although the difference in the sintering rate was not clear in the mixed powder compacts as well as in the case of iron-molybdenum system.
    (2) The neck growth rate followed the theoretical equation for volume diffusion controlled rate in both a and γ phases, and its rate was obviously divided into three groups at given sintering temperatures which were assigned to a, a+γ and γ phases.
    (3) Addition of W powder was found to be effective for densification of the mixed powder compacts sintered at high temperature of 1300°C, although there was little effect of its addition up to 1200°C because W slowly diffused to γ iron phase.
    (4) The neck growth rate of Fe-Ni alloy wires was nearly equal to that of pure iron in γ phase, and it was not so accelerated in the alloy wires as in the case of Fe-Ni mixed powder compact.
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  • Kanji Notomi, Nobuyasu Kawai
    1989 Volume 36 Issue 8 Pages 963-968
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    High-chromium steel powder containing 2.2%C-18%Cr-2%Mo-1%V, called "KAD181", has been produced by gas atomization, and hot isostatically pressed (HIPed) to full density.
    Microstructures and mechanical properties of as-HIPed KAD181 have been compared with those of HIPed and forged KAD181 and of conventionally cast and forged SKD11 steel (1.5%C-12%Cr). Bend strength, impact strength and fatigue properties of as-HIPed KAD181 are intermediate between those of longitudinal and transverse samples of as-forged KAD181. Wear resistance and fracture toughness of as-HIPed KAD181 are almost equivalent to those of as-forged KAD181 respectively. Mechanical properties of KAD181 are much superior to those of SKD11 except for fracture toughness, due to finer and prop homogeneous microstructure of KAD181.
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  • Masatomo Kamada, Masayuki Moriyama, Youichi Tokunaga
    1989 Volume 36 Issue 8 Pages 969-975
    Published: December 25, 1989
    Released on J-STAGE: May 22, 2009
    JOURNAL FREE ACCESS
    In order to improve the mechanical properties of sintered low alloy steels, Fe-1.5%Si-2.0%Ni-(0.5%Mo)-0.1-0.5%C compacts sintered at 1250°C for 3.6 ks were cooled in various conditions after the solution treatment at 960°C. The structures of specimens were controlled by changing the cooling rate. The relation between the structures which transformed during continuous cooling and the mechanical properties was studied. The results are summarized as follows:
    On the continuous cooling transformation diagram, the addition of molybdenum shifted the ferrite and pearlite noses to longer time and enlarged the sections of bainitic and martensitic transformations.
    It was necessary, under the optimum carbon content and cooling rate, to get the fine mixed structure of polygonal ferrite, bainitic ferrite and upper bainite which resulted in good combination of strength, ductility and toughness. But lower bainite and martensite appeared constantly in the structure of the specimens cooled in uniform cooling rate and decreased the ductility and toughness.
    The STEP cooling, which was the treatment of changing the cooling rate at 600°C, lead the fine mixed structure mentioned above containing 1025 vol% retained austenite. The STEP cooled specimens showed good mechanical properties; for example in 0.3-0.4%C specimen, 750 MPa of tensile strength, 8% of elongation and 120 kJ/m2 of Charpy impact value.
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