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Volume 52, Issue 10
Displaying 1-16 of 16 articles from this issue
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Hisanori Tanimoto, Saburo Nasu, Francisco Eiichi Fujita, Yoshinob ...1988 Volume 52 Issue 10 Pages 909-916
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSConversion Electron Mössbauer Spectroscopy (CEMS) is a useful technique to study structures and properties near the surface of materials. In this study, CEMS was applied to investigate around the surface of a high-manganese steel, which is called Hadfield steel which is known for its remarkable work hardening. X-ray backscattering Mössbauer spectroscopy was also performed in order to compare the state of the Fe atom near surface to that of bulk and the cause of work hardening of Hadfield steel was discussed.
Observed Mössbauer spectra were analyzed into two components, one was a singlet peak corresponding to Fe atoms without C atoms at the first or the second nearest neighboring interstitial site, the other a doublet peak corresponding to Fe atoms with C atoms at those sites. A widely split six line peak of α′ martensites was not observed in any Mössbauer spectra so that α′ martensites has no relation to work hardening of Hadfield steel. The comparison of CEMS spectra to X-ray backscattering Mössbauer spectra made it clear that the decarburization around the surface occurred even in the samples before working. The value of quadrupole splitting in CEMS spectra decreased by working and this could be explained by the introduction of stacking faults in samples. The decarburization around the surface and the decrease of quadrupole splitting by working lead to the conclusion that work hardening of Hadfield steel results from the introduction of stacking faults and the formation of thin ε martensites.View full abstractDownload PDF (1080K) -
Shicheng Liu, Hisashi Kuwano, Yoshikazu Hamaguchi1988 Volume 52 Issue 10 Pages 917-926
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe metastable R-phase precipitated in the early stage of aging in the Fe-Mo binary alloys is also observed in the Fe-Cr-Mo ternary alloys before the stable μ-phase, the Laves-phase, the χ-phase or the σ-phase is precipitated depending on the Cr and Mo contents and the aging temperature. The crystallographic structure and orientation relationship between the R-phase and matrix α-phase is quite similar to that in the Fe-Mo alloys. The replacement of Cr with Fe causes no effect on the precipitation process of the metastable R-phase but accelerates the transformation from the metastable R-phase to the χ-phase and delays the transformation to the stable σ-phase. The Mo content in the metastable R-phase, which is about 48 mass% in the case of the Fe-Mo binary alloy, decreases slightly with the increase of Cr content in the ternary alloys and shows 40 mass% in a Fe-10Mo-30Cr alloy. But no marked difference is observed in the Cr/Fe ratio between the metastable R-phase and as-quenched alloys.View full abstractDownload PDF (1635K) -
Shicheng Liu1988 Volume 52 Issue 10 Pages 927-934
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Precipitation processes in supersaturated Fe-5W-(0-34)Cr (at%) alloys during the aging between 823 and 1173 K have been studied mainly by means of X-ray diffraction, electron diffraction and electron microscopic observations. The major results obtained are as follows:
(1) During the aging at 823-1173 K, a metastable R-phase, which is similar to that in Fe-Mo binary alloys, is found in the early stage in Fe-5W-(12-34)Cr alloys, which is transformed to the Laves-phase, the χ-phase or the σ-phase in the later stage depending on the alloy composition and aging temperature. The composition of metastable R-phase is Fe-31W-(9-21)Cr.
(2) At 1173 K, the existence of χ-phase is confirmed but its composition is somewhat different from that in the literature. The three-phase region of (α+Laves+χ) exists near the Fe-corner in the 1173 K-isothermal section of the phase diagram.
(3) In the early stage of aging, there is an increase in hardness which might be due to the precipitation of metastable R-phase. In the later stage of aging, the successive hardening occurs in the high Cr alloys probably due to the transformation to the σ-Phase.View full abstractDownload PDF (1855K) -
Tetsuya Katayama, Hiroshi Fujita1988 Volume 52 Issue 10 Pages 935-944
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe formation mechanism of strain-induced γ→ε→α′ martensitic transformation in an Fe-Cr-Ni alloys has been investigated by electron microscopy. The results obtained are summarized as follows:
(1) Two sets of ε martensite crystals which belong to primary and coplanar slip systems are formed in γ-crystals which are oriented for multiple slip systems. They intersect with each other and fine α′ crystals are frequently formed at the intersections.
(2) Even when the γ-crystal is oriented for a single slip system and only one set of ε martensite crystals of a single variant are formed, α′ crystals are sometimes formed within them. In this case, stair-rod dislocations are observed so frequently in the vicinity of α′ crystals, accompaning the stacking faults which correspond to the secondary shear bands.
(3) The α′ crystals grow individually and consequently coalesce with each other to form a large single α′ crystal which contains complex microstructures including small ε martensite crystals.
The mechanism of γ→ε→α′ martensitic transformation is discussed on the basis of the experimental results.View full abstractDownload PDF (3688K) -
Toshio Shimoo, Fusago Mizutaki, Shigeru Ando, Hiroshi Kimura1988 Volume 52 Issue 10 Pages 945-953
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of reduction of silica-graphite mixtures has been investigated at temperatures between 1673 and 2073 K under argon atmosphere. The rate of reduction has been determined by thermogravimetry and chemical analysis. The reduction products are both SiC and SiO. The production ratio of SiC increases significantly with increasing temperature and C/SiO2 mixture ratio.
In the early stage of the reduction, the rate equation for interfacial reaction control is applicable to the reduction of SiO2 with graphite. The apparent activation energy is 361 kJ/mol. The rate determining step is considered to be the chemical process at the surface of graphite particles.
When the reaction proceeds and the continuous layer of SiC is formed around the graphite particles, the rate of reduction shows a parabolic rate equation. The activation energy is 426 kJ/mol. The reduction of SiO2 is controled by the diffusion of carbon in SiC.
At temperatures below 1773 K, the reduction rate cannot be represented by the above rate equations.View full abstractDownload PDF (1401K) -
Masakazu Fujitsuka, Masao Fukutomi, Masatoshi Okada1988 Volume 52 Issue 10 Pages 954-959
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe use of low atomic number (Z) material coatings for fusion reactor first-wall components has proved to be a valuable technique to reduce the plasma radiation losses. Molybdenum coated with titanium carbide is considered very promising since it has a good capability of receiving heat from the plasma. An interfacial reaction between the TiC film and the molybdenum substrate, however, causes a severe deterioration of the film at elevated temperatures.
In order to solve this problem a TiC coated molybdenum with an intermediate tungsten layer was developed. High temperature properties of this material was evaluated by a newly devised electron beam heating apparatus.
TiC coatings prepared on a vacuum-heat-treated molybdenum with a tungsten intermediate layer showed good high temperature stability and survived 2.0 s pulses of heating at a power density as high as 53 MW/m2.
The melt area of the TiC coatings in high heat flux testings also markedly decreased when a tungsten intermediate layer was applied. The melting mechanism of the TiC coatings with and without a tungsten intermediate layer was discussed by EPMA measurements.View full abstractDownload PDF (1175K) -
Toshio Katagiri, Kyoko Fujii, Mitsuyoshi Naritomi1988 Volume 52 Issue 10 Pages 960-965
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe ion-sulphonitriding of SCM440 steel was studied by using ammonium sulphide as a sulphonitriding reagent. The experiments were performed over the temperature range from 808 to 888 K in a gas mixture of nitrogen, hydrogen, and resolved ammonium sulphide atmosphere. From the microscopic examinations it was found that the sulphonitrided compound layer consisted of a black, porous layer and a white layer formed on the surface of the specimen. The phase compositions of the sulphonitrided layer obtained by heat treatment at 808 and 858 K were found to be FeS, ε-Fe2-3N, while those obtained at 858 K were FeS, ε-Fe2-3N and γ′-Fe4N by X-ray diffraction. Microhardness measurements on the cross-section of the ion-sulphonitrided specimen showed that the microhardness of the compound layer was HV 600∼700 on the surface, and HV 900∼1000 on the inner part of the layer, and it was considered that the microhardness of the layer had an increasing tendency from the surface toward the inner part of the layer.View full abstractDownload PDF (1315K) -
Katsunori Yamaguchi, Kimio Itagaki, Akira Yazawa1988 Volume 52 Issue 10 Pages 966-972
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHeat contents of the Ga-As and In-As systems were measured by a drop-calorimeter in the concentration ranges of NAs=0.05 to 0.5 (GaAs, InAs), and in the respective temperature ranges of 800 to 1550 K and 700 to 1500 K. The corresponding results were then illustrated in (HT−T298.15)-temperature-composition ternary diagrams. By the use of a thermodynamic analysis method, the thermodynamic quantities such as the activities of relating components and heats and entropies of mixing in the liquid Ga-As and In-As systems were determined at high temperatures above 1200 K, respectively. The activities of Ga and In in both liquid systems showed a large negative deviation from Raoult’s law at compound side and a slight positive deviation in the Ga-rich and In-rich regions, and those of As showed a large negative deviation from Raoult’s law. Based on the obtained thermodynamic data, partial pressure-temperature-composition correlation diagrams were constructed for the Ga-As and In-As systems. Total pressure of arsenic gas species and partial pressure of As2 showed a drastic increase with increasing temperature and increasing arsenic concentration.View full abstractDownload PDF (785K) -
Won Sub Chung, Takeaki Murayama, Yoichi Ono1988 Volume 52 Issue 10 Pages 973-980
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe reduction equilibria of monocalcium ferrite with CO-CO2 gas mixtures was measured using the following cell: Pt/CO-CO2/ZrO2(Y2O3)/A(O), B(O), C(O)/Pt
where A(O), B(O) and C(O) represent three solid phases which participate in the reduction equilibria. The composition of the CO-CO2 gas mixtures in the reference electrode was changed so that the electromotive force became zero. The gas composition at 0 mV was assumed to be the equilibrium one at the temperature.
The results obtained were as follows:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (1064K) -
Norikatsu Yokota, Shigehiro Shimoyashiki1988 Volume 52 Issue 10 Pages 981-988
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDeposition behavior of corrosion products has been investigated to clarify the effect of metal surface composition on the deposition process in liquid sodium. For the study a sodium loop made of Type 304 stainless steel was employed. Deposition test pieces, which were Type 304 stainless steel, iron, nickel or Inconel 718, were immersed in the sodium pool of the test pot. Corrosion test pieces, which were Type 304 stainless steel, 50 at%Fe-50 at%Mn and Inconel 718, were set in a heater pin assembly along the axial direction of the heater pin surface. Sodium temperatures at the outlet and inlet of the heater pin assembly were controlled at 943 and 833 K, respectively. Sodium was purified at a cold trap temperature of 393 K and the deposition test was carried out for 4.3×102-2.9×104 ks.
Several crystallized particles were observed on the surface of the deposition test pieces. The particles had compositions and crystal structures which depended on both the composition of deposition test pieces and the concentration of iron and manganese in sodium. Only iron-rich particles having a polyhedral shape deposited on the iron surface. Two types of particles, iron-rich α-phase and γ-phase with nearly the same composition as stainless steel, were deposited on Type 304 stainless steel. A Ni-Mn alloy was deposited on the nickel surface in the case of a higher concentration of manganese in sodium. On the other hand, for a lower manganese concentration, a Fe-Ni alloy was precipitated on the nickel surface. Particles deposited on nickel had a γ-phase crystal structure similar to the deposition test piece of nickel. Hence, the deposition process can be explained as follows: Corrosion products in liquid sodium were deposited on the metal surface by forming a metal alloy selectively with elements of the metal surface.View full abstractDownload PDF (935K) -
Nobuo Kobayashi, Yoshio Yamasaki, Naotsugu Inakazu1988 Volume 52 Issue 10 Pages 989-994
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to find the relation between corrosion behavior and residual stress, the immersion test of aluminum sheet (99.99%) which was cold-rolled up to 90% total reduction under the condition of 10 and 30% reductions per pass, has been carried out in 0.5 N NaOH aqueous solution, and the residual stress and the rolling texture have been investigated by means of X-ray diffraction. The corrosion rate curve obtained showed two maximum values at 30 and 80% total reductions, and a minimum value at 50%. The maximum value at 80% is larger than that at 30%, and the corrosion rate decreases with increasing one-pass reduction. The relation between residual stress and total reduction corresponded to the relation between corrosion rate and total reduction; it was found that the corrosion rate depends on the residual stress. The residual stress increases with increasing dislocation density and tangle up to the 30% total reduction. And at about 80% total reduction, it increases in accordance with the formation process of the rolling texture. On the other hand, ths residual stress at 50% total reduction falls by the release of strain energy due to lattice rotations with deformations over 30%. When the cold-rolled sheet was recovered (373 K, 10.8 ks), the corrosion rate becomes a relatively average velue and is lower than that of the as-rolled sheet.View full abstractDownload PDF (1409K) -
Kazuyoshi Kamachi, Sachio Oki, Susumu Gohda, Gunji Ueno1988 Volume 52 Issue 10 Pages 995-998
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermal spraying method is one of the industrial processes to improve wear resistive, heat resistive and corrosion resistive properties of the surfaces of metals and alloys. In spite of widely spreaded applications of the method, any study of the cohesivity of thermal sprayed layer with substrate from a standpoint of the basic cohesive mechanism has not been carried out. The cohesivity is expected to be enhanced by mutual diffusion between coated material and substrate. In this paper, reaction diffusion between thermal sprayed aluminium and copper substrate is reported. 99.9% aluminium was thermal sprayed on commercial copper plates by the wire arc spraying method. The aluminium coated specimens were heat treated at 873 K for 3.6 ks in a muffle furnace under the atmosphere. Micro-structure, Vickers hardness, X-ray diffraction patterns of the cross sections of the specimens were examined and the distributions of aluminium and copper were analysed by EPMA. It was proved that reaction diffusion occurred between the thermal sprayed aluminium layer and the copper substrate and the intermetallic compounds of Al-Cu were formed. The thickness of the alloy layer formed by the heat treatment at 823 K for 3.6 ks was about 140 μm and the maximum hardness of the alloy layer was about 700 Hv.View full abstractDownload PDF (858K) -
Sachio Oki, Kazuyoshi Kamachi, Susumu Gohda, Yoshito Hirata1988 Volume 52 Issue 10 Pages 999-1005
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn this study 99.9% aluminium was thermal sprayed on the specimens of 0.25%C (S25C) and 0.55%C (S55C) steels by the wire arc spraying method. Armco iron specimens were also coated with aluminium to examine the effect of carbon on the diffusion process. These specimens were heat treated at temperatures from 923 to 1123 K for 3.6 and 10.8 ks in the atmosphere using a muffle furnace. The microstructure and Vickers hardness of the heat treated specimens were examined. Identification of the formed phases was carried out by X-ray diffraction patterns and EPMA.
Results obtained were as follows:
(1) Diffusion of aluminium into the substrates occurred and diffusion of iron from the substrate also occurred. Intermetallic compounds of Fe-Al were formed and the total thickness of the alloy phases formed by the heat treatment at 923 K for 10.8 ks was about 250 μm.
(2) Several intermetallic compounds formed in the alloy layer were identified by the X-ray diffraction method. The compounds were arranged in order of stoichiometric atomic ratio in the interface zone between the coated aluminium layer and the substrate, and the Fe2Al5 phase was predominant over other phases. The maximum value of the Vickers hardness of the diffused layer attained about 1000.
(3) In the case of armco iron, the growth of the alloy phases was not uniform. However, in the case of carbon steels, it was comparatively uniform. This may be attributed to the diffusion of aluminium in carbon steels was suppressed by carbon atoms.View full abstractDownload PDF (1799K) -
Ken-ichi Ohsasa, Tadayoshi Takahashi, Katuhiro Kobori1988 Volume 52 Issue 10 Pages 1006-1011
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe negative pressure developed in the liquid retained in solidifying aluminum ingots has been directly measured. A stainless steel disk of 50 mm diameter was immersed into the depth of 5 mm from the surface of the aluminum melt 70 mm high in a graphite crucible of 60 mm diameter. When the solidification front reached the edge of the disk, the negative pressure started to occur in the residual liquid because the liquid under the disk was blockaded. The negative pressure was continuously measured with the load cell connected to the disk and the critical value of the negative pressure for pore formation was evaluated from the peak of the measured load curve.
The negative pressures for the pore formation in the most ingots were smaller than 10−2 MPa, but in a few ingots relatively large negative pressures up to the 2.4×10−1 MPa were measured. The external shrinkage of the solidified shell due to the negative pressure was observed in the ingots with large negative pressure.View full abstractDownload PDF (949K) -
Ken-ichi Ohsasa, Tadayoshi Takahashi1988 Volume 52 Issue 10 Pages 1012-1019
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRadial contraction behavior during solidification of cylindrical Al-3 mass%Si alloy ingots with and without degassification was investigated in relation to pouring temperatures. The macrostructure of the conventionally cast ingots changed from columnar to fine equiaxed morphology with decreasing pouring temperature, and the fraction solid of solidifying shell corresponding to the beginning of contraction varied concurrently from 0.56 to 0.77. The amount of contraction of the ingot till the end of solidification decreased with decreasing pouring temperature, and the amount of the contraction of the degassed ingot was larger than that of the non-degassed ingot at the same pouring temperature.
The comparison between the measured contraction and the estimated thermal contraction showed that the amount of the contraction of solidifying shell consisted of two components, i.e. thermal contraction of dendrite network and the solid deformation due to negative pressure developed in interdendritic liquid. Furthermore, it was shown that the density of the ingot with a large contraction was higher than that of the ingot with a small contraction.View full abstractDownload PDF (1590K) -
Mok-Soon Kim, Shuji Hanada, Sadao Watanabe, Osamu Izumi1988 Volume 52 Issue 10 Pages 1020-1021
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (433K)
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