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Volume 41, Issue 4
Displaying 1-17 of 17 articles from this issue
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Seiki Nishi, Toshir\={o} Kobayashi, Fumio Nonoyama1977 Volume 41 Issue 4 Pages 319-325
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relationships between the toughness and the cast structures were investigated in Al-0.5 wt% iron alloys with varying amounts of titanium or chromium, cooled at different rates.
The addition of Ti refined and that of Cr coarsened the grain size. On the contrary, the addition of Ti coarsened and that of Cr refined the dendrite cell size. No clear difference in the toughness at room temperature was observed in all specimens. But the toughness at −196°C changed with the dendrite cell size rather than with the grain size. It was assumed that the toughness was enhanced by the refining of the dendrite cell size.
As desribed above, the addition of Ti, which is practiced in the commercial production, does not always seem to be effective for the improvement of toughness. It would be necessary, therefore, to introduce some way of refining the dendrite cell size.View full abstractDownload PDF (720K) -
Minoru Mori, Yoichi Ishida, Masao Kato1977 Volume 41 Issue 4 Pages 326-332
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBurgers vector of a boundary dislocation in a recrystallized Al-Mg alloy was identified by comparing the transmission electron micrographs with two-beam dynamical theory computations.
A large angle goniometer stage was used to observe the specimen from various directions and the crystal orientations were determined by matching the diffraction pattern with the computed Kikuchi map on a graphic display. The image comparison showed that the particular dislocation is one of the b3-type Burgers vectors whose magnitude is especially large. The direction and the spacing of the dislocation agreed with those of the dislocation network that can cause the measured misorientation from that of the perfect Σ33 coincidence. The calculation indicated that two more arrays of boundary dislocations of small Burgers vectors are in the boundary.
It is concluded that the dislocation array is only occasionally seen in the boundary of a polycrystalline specimen not because the array is absent but because the image is invisible in the micrograph.View full abstractDownload PDF (789K) -
Tohru Arai, Yoshihiko Sugimoto, Masayoshi Mizutani, Noboru Komatsu1977 Volume 41 Issue 4 Pages 332-338
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the previous paper, it was reported that carbide such as VC, NbC, Cr7C3, etc. can be formed on steels immersed in a borax bath containing metal powder such as Fe-V, Fe-Nb or Cr.
The present study was undertaken to investigate the possibility of carbide formation on steels immersed in a borax bath containing chloride or oxide powders such as VCl3, CrCl3, V2O5, Nb2O5 or Cr2O3 and a combination of oxide and metal powder such as Ca, Ti, Fe-Al, Fe-Mn, etc.
The results obtained are as follows:
(1) The carbide layer was formed on steels immersed in the bath containing chloride powder of VCl3 or CrCl3.
(2) In the bath containing oxide powder of V2O5, Nb2O5 or Cr2O3, the carbide layer was not formed, while the layer was formed in the bath containing a combination of oxide powder and metal powder as a reducing agent, which provides a carbide forming reaction with negative free energy change (ΔG).
(3) The use of a large amount of metal powder in the above-mentioned reaction, however, resulted in the formation of the iron boride layer instead of the carbide layer.View full abstractDownload PDF (757K) -
Shigeru Asano, Ryutaro Tsunoda, Rikuro Otsuka1977 Volume 41 Issue 4 Pages 338-344
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe temperature dependence of internal friction was measured from 100 to 350 K at a frequency of about 700 Hz for hydrogen-charged 310S, 316 and 304 stainless steels. A characteristic relaxation peak due to dissolved hydrogen was found at about 280 K, on which there is little information in the literature. The characteristics of this 280 K peak are as follows: (1) The internal friction peak grew up with hydrogen charging and went to decay with room-temperature aging, the time responses of which were consistent with a diffusion-controlled process. The peak hight increased not only with the absorbed volume of hydrogen but also with the nickel content of alloys. (2) The peak temperature, in contrast to the peak hight, did not depend much on the absorbed volume of hydrogen and the compositon of alloys. From the relation between peak temperature and test frequency, the activation energy was estimated to be 11.8 kcal/mol and the frequency factor to be 1.3×1012 s−1. Both of these values agreed quite well with the corresponding values for hydrogen diffusion in austenitic stainless steels. (3) Apparently, the 280 K peak could be regarded as a Snoek-type relaxation occurring in the fcc lattice, which might be explained in terms of the stress-induced reorientation of hydrogen atom pairs or clusters under the influence of nickel in Fe-Cr-Ni alloys.View full abstractDownload PDF (638K) -
Jiro Saga, Setuo Miyata1977 Volume 41 Issue 4 Pages 345-352
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the mechanism of hydrogen embrittlement in nickel and nickel-iron alloys, tensile tests at various temperatures and strain rates were carried out using thin specimens occluded with hydrogen in the form of solid solution and hydride.
Embrittlement occurred over the whole investigated temperature range of −196 to +100°C, revealing two maxima near −50°C and ambient temperatures. In lower testing temperatures where the hydride is stable, supersaturated hydrogen in the form of solid solution is segregated to grain boundaries or high triaxial stress fields, precipitating hydride during the tensile test. Embrittlement near −50°C decreases with the increase in iron content and strain rate, since they make hydride precipitation difficult. On the other hand, in the higher testing temperature range where the hydride is unstable, embrittlement is accelerated not only by the generation of structural damage like surface cracks caused by the decomposition of the unstable hydride but also by the segregation of the hydrogen to regions of triaxial stresses around the damage. Embrittlement of this type occurs more pronouncedly during aging at 20°C; the ductility of hydrogenated metals decreases with hydride decomposition, showing a minimum when the hydride has been decomposed completely.
Hydrogen embrittlement is considered to take place by two distinct causes; one is precipitation of brittle hydride, and the other is the clustering of hydrogen around the metallographic damage introduced by hydride decomposition.View full abstractDownload PDF (940K) -
Kazuhiko Majima, Hiroyasu Mitani1977 Volume 41 Issue 4 Pages 352-358
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn this work, the continuous cooling transformation diagrams of the Fe-Cu-1.0%C sintered Cu steel containing up to 6.5%Cu were investigated, and the effect of Cu on the critical cooling rate was made clear. Subsequently, in order to investigate the difference between the hardenability of the normal wrought steel and that of the sintered steel, the continuous cooling transformation diagram of the eutectoid carbon steel practically free from impurities, produced by vacuum melting method, was studied.
The results obtained were summarized as follows:
(1) The critical cooling rate of the Fe-1.0%C binary sintered compacts was as fast as 1100°C/sec, indicating poor hardenability.
(2) The critical cooling rate of the Fe-Cu-1.0%C ternary sintered compacts became slower with increasing Cu content. For example, it was 140°C/sec in the case of the Fe-6.5%Cu-1.0%C ternary sintered compacts whose composition was nearly the same as the Fe-Cu-C ternary eutectoid composition.
(3) The critical cooling rate of the normal wrought Fe-0.77%C steel with 0.75%Mn and 0.2%Si was 150°C/sec, while, it was 900°C/sec in the case of the Fe-0.77%C steel practically free from impurities.View full abstractDownload PDF (728K) -
Toshio Hirai, Koichi Niihara, Takashi Goto1977 Volume 41 Issue 4 Pages 358-367
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPyrolytic Si3N4 has been deposited on a graphite substrate using a SiCl4+NH3+H2 system as the source material under the following conditions: SiCl4(vapor) flow rate [FR(SiCl4)], 100, 170 and 260 cm3/min; SiCl4(v) to H2 gas flow rate ratio FR(SiCl4)/FR(H2), about 0.26; NH3 gas flow rate, 60 cm3/min; total gas pressure (Ptot), 10 to 80 Torr; deposition temperature (Tdep), 1100 to 1500°C. The effects of the SiCl4(v) flow rate on the morphology, density, structure and deposition rate of Py-Si3N4 were investigated.
At Ptot=60 Torr, the rate of increase in layer thickness (x⁄t) became larger with FR(SiCl4). The maximum value (1.2 mm/hr) of x⁄t for the crystalline Py-Si3N4 was obtained at FR(SiCl4)=260 cm3/min, Tdep=1400°C and Ptot=60 Torr. The density of the amorphous Py-Si3N4 was 2.60 to 2.89 g/cm3 at FR(SiCl4)=170 cm3/min, and 2.90 to 3.00 g/cm3 at 100 and 260 cm3/min. The observed density of the crystalline Py-Si3N4 was independent of the SiCl4(v) flow rate and 3.15 to 3.18 g/cm3 (99 to 100% of a theoretical density). The structural characteristics and formation mechanism of Py-Si3N4 were also discussed in terms of the SiCl4(v) flow rate.View full abstractDownload PDF (1022K) -
Toshio Hirai, Koichi Niihara, Akira Ohkubo1977 Volume 41 Issue 4 Pages 367-374
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMixtures of α- and β-type silicon nitride powders and carbon powder (C/Si3N4 mole ratio=3.0) have been heat treated in the temperature range of 1320 to 1760°C for 0 to 120 hr in N2 at atmospheric pressure. The amounts of SiC formed by a reaction of Si3N4+3C→3SiC+2N2 under various conditions were determined by chemical and X-ray diffraction analyses. For the α-Si3N4-C system (C/α-Si3N4=0 and 3.0), the amount of the α→β transformation was obtained from X-ray diffraction data. In both systems, SiC was formed at temperatures above 1490°C and the greater part of SiC was of the β-type. The experimental data on the formation rate of SiC followed Jander’s solid-state kinetic law. The β-Si3N4 was more reactive with carbon than the α-Si3N4 at high temperatures. The rates of SiC formation in the β-Si3N4-C system were larger than that for the α-Si3N4-C system by factors of 2 (at 1800°C) to 5 (at 1500°C). The activation energies in Jander’s kinetics were 160 and 190 kcal/mol in the β and α systems, respectively. It is concluded that the rate-controlling step for the high-temperature reaction of Si3N4 with carbon is the diffusion of carbon in the SiC formed. The difference between the reactivities of α- and β-Si3N4 with carbon is also discussed in terms of the α→β transformation.View full abstractDownload PDF (584K) -
Yasunari Kaneko, Yukio Suginohara1977 Volume 41 Issue 4 Pages 375-380
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA fundamental study was carried out in order to find out the method of fixed quantity on three kinds of oxygen ions, i.e. O0 (bridged oxygen), O− (non-bridged oxygen) and O2− (free oxygen), exsisting in the vitreous silicate. Therefore, the binding energies of oxygen Ols electrons for various oxides and mono-silicate compounds were determined by using X-ray photoelectron spectroscopy (XPS). The main results obtained were as follows:
(1) The binding energies of Ols electrons for O2− ion existing in various metallic oxides generally decreased with decreasing electronegativity of metallic ion and ion-oxygen attraction.
(2) The shift of Ols binding energy for O2− ion in MeO was about two times as many as that for O− ion in 2 MeO·SiO2 compounds, when those were based on the Ols binding energy for O0 ion in SiO2.
(3) The XPS spectra obtained for binally silicates showed that the Ols spectra fitted three overlapped peaks, when all the peaks were constrained to the Lorentz shape and the values of Ols binding energy and width at half-maximum obtained for three kinds of oxygen ions, by the use of an electronic computer. Consequantly, the quantitative analysis of O0, O− and O2− ions existing in the binally silicate may be possible.View full abstractDownload PDF (499K) -
Toshimi Sasaki, Toshihiro Yamada, Akiomi Kono, Masahisa Aoyagi1977 Volume 41 Issue 4 Pages 381-385
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe elements such as Al, Cr and Ti that form the stable nitride on the process of gas nitriding are necessary to obtain higher surface hardness and larger nitrided depth, as standarized in the chemical composition of nitriding steel.
Similarly, Si is an element to form nitride. Therefore, the authors have shown in the previous paper that a higher surface hardness, Hv 800, is obtained in the gas nitrided spheroidal graphite cast iron and considered that its hardening mechanism depends on the formation of Si3N4.
A more detailed study of the effect of Si content on the gas nitriding characteristics was conducted in this work.
The 0.2%C steels containing 0.37∼1.49%Si were gas nitrided at 530∼620°C for 20 hr using a circular type furnace.
It was found that the surface hardness of nitrided specimens increases in propotion to the increase of Si content, and that the surface hardness reaches a maximum value, about Hv 400. The nitrided depth increases with increasing of Si content and nitriding temperature. The maximum value of this depth is about 0.4 mm.
Moreover, it was found that tempering the nitrided specimens increases both the surface hardness and the nitrided depth.
From these results, we concluded that the hardening mechanism in those gas nitrided specimens was due to the precipitation or growth of Si3N4.View full abstractDownload PDF (851K) -
Shigeatsu Nakazawa1977 Volume 41 Issue 4 Pages 386-390
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSActivity coefficients of silver in infinitely dilute solution with copper, γAg°, were determined by the “Two-Component Evaporation Method”, where γAg° was determined combining the composition of the equilibrium vapor, the alloy composition, and the known vapor pressures of components in each standard state, pAg° and pCu°. For a dilute solution this method is similar in principle to that reported by Onillon and Olette for determination of the activity coefficients of various components in molten iron. This study, however, has two unique features; (1) the equilibrium vapor effuses from a “Knudsen cell,” and (2) the ratio of the “logarithmic decrements” of each component during the experiment is measured. The “logarithmic decrement” is defined as ΔlnmAg or ΔlnmCu, where mAg or mCu is the mass of respective component in the alloy, and related to γAg° by the equation
(This article is not displayable. Please see full text pdf.)
\ oindentwhich can be successfully used to overcome the problems caused by the alloy composition change during the run.
Experiments were done at three temperatures, i.e., 1480, 1580, and 1680 K. Silver concentrations of all nine alloys investigated were 1 at% at the highest. If a proportional relationship between lnγAg° and 1⁄T is accepted a priori, a least-squares analysis of the values ΔlnmAg⁄ΔlnmCu for the alloys at different temperatures gives the equation
(This article is not displayable. Please see full text pdf.)
\ oindentwhich yields lnγAg°=1946 K⁄T. Activity coefficient is estimated as follows: γAg°=3.75 (at 1473 K), 3.44 (1573 K), or 3.20 (1673 K).View full abstractDownload PDF (402K) -
Hideo Ohno, Yoshiaki Tsunawaki, Norimasa Umesaki, Kazuo Furukawa, Nobu ...1977 Volume 41 Issue 4 Pages 391-396
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe self-diffusion coefficients and their temperature dependences of fluorine in molten Li2BeF4 and LiBeF3 have been investigated by the capillary reservior technique using a tracer Fluorine-18. The observed diffusion coefficients of fluorine DF (cm2 sec−1) are written in the form of DF=D0exp[−ED(F)⁄RT], where ED(F) and D0 are calculated by the least squares method from all experimental data. Those of molten Li2BeF4 and LiBeF3 are as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentThese results for fluorine diffusion are considerably difficult to explain by a simple model because of the unusual combination of the relatively large diffusion coefficients and a high activation energy and cannot be explained solely by mass transfer due to migration of large fluoroberyllate anions. One of the possible explanations for these results could be the exchange of fluorine atom between neighboring beryllate units including the rotation of beryllate anions. Another possible explanation could be the diffusion mechanism of a neutral pair of, for example, LiF. Both diffusion mechanisms give high activation energy and are consistent with the observed results. The close analogy between the diffusion behavior of fluorine in molten LiF-BeF2 mixture and that of oxygen in molten CaO-SiO2-Al2O3 slag was also discussed.View full abstractDownload PDF (524K) -
Kazuji Sasa, Tadayuki Nakayama1977 Volume 41 Issue 4 Pages 396-400
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the present study, scaling behaviours of Fe-18Cr and Fe-18Cr-C alloys, especially effects of the alloy grain size and its growth at 900 and 1000°C in 760 Torr oxygen were examined by thermogravimetric methods, X-ray diffraction and electron probe microanalysis. At 1000°C, breakaway oxidation due to a matrix grain growth was observed for fine grained Fe-18Cr and this was suppressed for coarse grained specimens which had been prepared by annealing at 1200°C for 5 hr. However, the oxidation behaviour of the coarse grained Fe-18Cr containing 0.057%C as well as the fine grained specimens containing 0.10%C showed the development of nonprotective oxide scales. The grain growth of Fe-18Cr and Fe-18Cr-C was not remarkable at 900°C, and the fine grained Fe-18Cr produced only Cr2O3-rich scales. Moreover, the oxidation behaviour of the coarse grained specimens followed an approximate parabolic rate law. Both the fine and coarse grained Fe-18Cr-C alloys showed the breakaway oxidation behaviour even at 900°C, and produced rapid growing stratified scales composed of the outer Fe oxide layer and the inner Fe, Cr spinel layer. The formation of the nonprotective oxide scales on the Fe-18Cr-C specimens may be mainly attributed to the decarburization from the alloys at high temperatures.View full abstractDownload PDF (674K) -
Yasuyoshi Fukui, Yakichi Higo, Shigetomo Nunomura1977 Volume 41 Issue 4 Pages 400-405
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA study has been made of the crystallographic dependence of fatigue crack propagation in bcc metals using Fe-3%Si alloy coarse grain specimens. A significant crystallographic dependence in fatigue crack propagation is observed. Fatigue cracks do not propagate stably along an unspecific plane normal to the loading axis but incline to change the propagation plane gradually to propagate along a specific plane ({110} or {100}). In this grain, the fatigue striation arrangement direction is changed according to the change of the fatigue crack plane. Analyzing this result, it is revealed that the striations are arranged parallel to the cross-line between a macroscopic crack plane and the {110} or {100} plane.
Various fatigue crack propagation models are discussed in the light of this study, and it is shown that no fatigue crack propagation model can explain adequately this crystallographic dependence. This may be explained by modifying the so-called slip-off process.View full abstractDownload PDF (773K) -
Shigetomo Nunomura, Yasuyoshi Fukui1977 Volume 41 Issue 4 Pages 405-412
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOn the basis of the observed cristallographic features of the fatigue crack propagated planes in Fe-3%Si single crystals, the transcrystal fatigue crack propagation mechanism of bcc metals was studied. To make sure the one cycle-one striation relation which forms a basis of the fatigue crack propagation, program load fatigue tests were carried out. The relation was confirmed all over the fatigue cracked surfaces. The dependence of crystallographic orientation on the crack propagating rate and the direction of the propagation was investigated using the coarse-grain thin plate specimens. The two dimensional slip-off process model was modified under the three dimensional condition, taking the shear stresses on slip planes into account. This model shows that the crack plane and the fatigue striation have a tendency to coincide with {110} and ⟨111⟩ respectively, where the rate reaches a maximum value. The model also shows that this tendency appears slowly in polycrystals, and that the effect of the stress ietensity factor of the whole specimen and that of the local one are in equilibrium with each other and the fatigue crack plane and the striation can lie on an unspecified plane and direction respectively in single and coarse grain crystals. These were in good agreement with the observations. Considering the strain hardening in the cracking process, the variety of the contrast and the profile of the striation could be explained.View full abstractDownload PDF (924K) -
Masahiro Kitada1977 Volume 41 Issue 4 Pages 412-420
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAbsorption-desorption characteristics of hydrogen, e.g. the enthalpy changes, the absorption and desorption rates, for LaNi5, CeCo5, and SmCo5 noticed as hydrogen storage materials have been studied.
The results are as follows:
(1) Hydrides formed under 5 atm of hydrogen at 20°C are LaNi5H7.72, CeCo5H2.45 and SmCo5H2.90.
(2) The enthalpy changes for the formation of the hydrides (hydrogen absorption) in the LaNi5-H, CeCo5-H, and SmCo5-H systems are −6.76, −7.49, and −7.93 kcal/mol, and the enthalpy changes for the dissociation of the hydrides (hydrogen desorption) are 6.56, 7.24, and 7.35 kcal/mol, respectively.
(3) The desorption rates of hydrogen against the air of 1 atm from the hydrides decrease with decreasing temperature, and the apparent activation energies of the hydrogen desorption obtained from the relations between the desorption rate and inverse temperature are 11.3–11.7 in the LaNi5-H, 10.1–15.2 in the CeCo5-H, and 4.1–14.3 kcal/mol in the SmCo5-H systems. On the hydrogen desorption from the hydride in the LaNi5-H system, the following relation is obtaind empirically; νd=B·Pd2, where νd, Pd, and B are the hydrogen desorption rate, the equilibrium hydrogen desorption pressure, and a constant, respectively.
(4) On the hydrogen absorption in the LaNi5-H system, the following relation is obtained empirically; νa=A(Pa−Pe), where νa, Pa, Pe, and A are the hydrogen absorption rate, the applied hydrogen pressure, the equilibrium hydrogen absorption pressure, and a constant respectively. The absorption rates increase with decreasing temperature, and the apparent activation energy of the hydrogen absorption is about 3 kcal/mol.View full abstractDownload PDF (996K) -
Masahiro Kitada1977 Volume 41 Issue 4 Pages 420-425
Published: 1977
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe equilibrium hydrogen absorption and desorption pressures, the hydrogen absorption and desorption rates, and the other characteristics of Mm-Ni alloys have been studied to appraise as hydrogen storage materials. In this study, it is clear that Mm-Ni alloys have good practical characteristics. Mm-Ni alloys containing 65 to 67 wt%Ni absorb the maximum amounts of hydrogen in the Mm-Ni system. For example, Mm-67 wt%Ni alloy forms the hydride MmNi4.95H6.95 at 20°C, and the equilibrium hydrogen absorption and desorption pressures are 20 and 10 atm respectively. The enthalpy changes of hydride formation and dissociation for Mm-67 wt%Ni alloy are −5.0 and 4.1 kcal/mol, and the apparent activation energies of hydrogen absorption and desorption are 6.1 and 8.6 kcal/mol respectively.View full abstractDownload PDF (581K)
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