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Volume 44, Issue 6
Displaying 1-19 of 19 articles from this issue
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Tsuneo Saga, Shuji Nagai1980 Volume 44 Issue 6 Pages 589-593
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHot-rolled thick plates of A5083P-0 with anisotropy were used as work pieces, and the cutting resistance, the shear angle, the cutting work were measured under orthogonal cutting.
And also, the effects of anisotropy of work piece on the behavior of built-up edge and the shape of free surface of chip were observed.
Results obtained were as follows:
(1) Due to anisotropy of the work piece, effect of cutting direction on tangential force was markedly observed; the observed effect was L>LT\fallingdotseqST.
Compared with L-direction cutting, in the case of LT and ST-direction cuttings, the tangential force decreased about 12%. Radial force was almost the same regardless of the cutting direction.
(2) Shear angle φ, shear stress in shear plane τs, compressive stress σ and work of shearing deformation in the shear plane Es under orthogonal cutting were affected by anisotropy same as the tangential force.
(3) Mechanism of cutting with built-up edge was analyzed, and the following results were obtained. True rake angle α′, shear angle φ and contact length l show the tendency of L<LT\fallingdotseqST. Over cut ψ, contact width u shows L>LT\fallingdotseqST, and the cutting resistance in L-direction was greater than that in LT and ST directions.
(4) In the case of L-direction cutting as compared with ST-direction cutting, tool mark does not coincide with cutting direction and has waving, and lamella intervals are large. This fact is considered to be one of the causes which make the cutting resistance of L-direction large.
Where L=Longitudinal LT=Long Transverse ST=Short Transverse.View full abstractDownload PDF (573K) -
Teruaki Sato1980 Volume 44 Issue 6 Pages 594-602
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThere exists a large demand for a high carbon steel because of its high hardness and tensile strength accompanied by superior wear resistance. It is generally used as tough structures after heat treatment. However, in some cases it is used in as rolled structure. Welding is usually avoided for high carbon steel, but sometimes it is inevitable.
In the present paper, investigation has been made on the relation of microstructure and mechanical properties at various points of welded joint to fatigue properties by making the welded joint from two prior structures, heat treated tough structure and as rolled pearlite structure. The following results are obtained.
(1) The fatigue strength, microstructures and mechanical properties of the bonded portion for the welded joint of prior sorbitic structure are not so different from those of the weld metal compared to the case of prior pearlite structure.
(2) The plane and notched fatigue strength of the bonded portion are the lowest of all for both welded joints of prior sorbitic structure and pearlite structure.
(3) As for the heat affected zone and mother metal, the plane and notched fatigue strength and also the mechanical properties of the welded joint for prior sorbitic structure are superior to those for pearlite structure.
(4) The fatigue strength and endurance ratio of a sorbitic structure are higher than those of a pearlite structure.
(5) The endurance ratio of weld metal, HAZ and mother metal except bonded portion are about 0.37∼0.39 and the welded joint of prior sorbitic structure is superior to that of pearlite structure.
(6) The fatigue strength of each location except bonded portion is proportional to the tensile strength for plane specimens but not for notched specimens.
(7) The reason why the fatigue strength of the bonded portion is low is that there appears the coase grained pearlite structure with ferrite network at the heat affected zone and the fatigue crack initiates at the locally weakest position, i.e. the ferrite phase. The hardness is the highest and the fatigue strength is the lowest for the bonded portion.
(8) The higher the hardness, the better the plane and notched fatigue strength in case of the same microstructure. The better the spheroidization of cementite, the higher the fatigue strength in case of the same hardness.View full abstractDownload PDF (1974K) -
Atsushi Takei, Kazuyoshi Nii1980 Volume 44 Issue 6 Pages 603-608
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo study the effect of tensile stress on the high temperature oxidation of alloys, wire specimens of Ni-20Cr-4Al alloy were oxidized in a creep testing machine under constant loads of zero to 14.7 MPa at 1237 K.
The results of the study indicated that under the tensile stresses of about 7.4 MPa protective thin oxide film of Al2O3 formed firmly and the oxidation rate showed a minimum. However, increasing the tensile stress beyond this stress range caused a severe oxidation penetrating the alloy matrix. From the present study, two mechanisms for the stable formation of a protective thin film of Al2O3 under these tensile stresses are proposed as follows.
(1) Tensile stress induced in a specimen by the constant load relieves the compressive stress being induced in the glowing oxide film, preventing the spalling of a thin oxide film of Al2O3 on the specimen surface.
(2) The tensile stress causes a significantly increased diffusion rate of Al in the alloy matrix, and the protective oxide film of Al2O3 easily forms on the surface of alloy.View full abstractDownload PDF (900K) -
Yukihiro Ueno, Rikuro Otsuka1980 Volume 44 Issue 6 Pages 609-615
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe thermally stimulated exoelectron emission (TSEE) from the oxidized surface of nickel, the cleavage plane of NiO single crystal and the pressed disk of nickel oxide powder was investigated using a gas-flow G.M. counter. These specimens showed the same TSEE behaviour and gave the glow curves having glow peaks at 400 and 520 K. The intensity of 520 K peak was nearly constant independent of the atmospheric pressure at which specimens were oxidized or heat-treated prior to the TSEE mesurement, while the intensity of 400 K peak varied with the atmospheric pressure and was proportional to the 6th root of the pressure. This fact implies that the 400 K peak intensity is in direct proportion to the concentration of nickel ion vacancy in NiO. It was revealed that the exoelectron source giving the 400 K peak was closely related to the nickel ion vacancy. This correlation was also shown in the variation in the peak intensity with the heat-treatment temperature range up to about 850 K. The peak intensity, however, decreased as the specimen was heated above 850 K, in spite of the high vacancy concentration. It was surmised that other factors became predominant in the case of high vacancy concentration.View full abstractDownload PDF (585K) -
Masao Yakushiji, Yoshiyuki Kondo, Kiyoshi Kamei1980 Volume 44 Issue 6 Pages 615-619
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCopper-nickel-titanium ternary alloys containing up to 45% nickel and 35% titanium were examined by means of optical microscopy, melting point measurement and X-ray diffraction to clarify the reactions with melt. The results obtained are as follows:
(1) The T phase based on the ternary compound CuNiTi having a melting point of 1458 K exists in this system.
(2) The primary surface of T comprises the greater part of the liquidus surface in the copper-rich region, and the eutectic reactions of T occur with α, Ni3Ti, CuTi, Cu3Ti2 and Cu3Ti.
(3) The mono-variant eutectic line represented by L\ ightleftharpoonsT+α runs along the copper-nickel binary system with falling temperature, and through the composition of Cu88%-Ni6%-Ti6% reaches the region where the lowest melting temperature is measured. The melt disappears in this region by the invariant eutectic reaction L\ ightleftharpoonsT+Cu3Ti2+Cu3Ti which seems to occur at about 1143 K.
(4) Two other invariant reactions L+α\ ightleftharpoonsT+Cu3Ti and L+TiCu\ ightleftharpoonsT+Cu3Ti2 occur at points close to the ternary eutectic point.View full abstractDownload PDF (706K) -
Masao Yakushiji, Yoshiyuki Kondo, Kiyoshi Kamei1980 Volume 44 Issue 6 Pages 620-624
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Cu rich Cu-Ni-Ti ternary alloys contaning up to 45%Ni and 35%Ti were exsmined to clarify the phase relationship by means of X-ray diffraction technique and electron probe microanalysis. The constitution of Cu-T quasi-binary system was also investigated. The results are summarized as follows:
(1) In the Cu rich region, the T phase based on the ternary compound CuNiTi is in equilibrium with α, Cu3Ti, Cu3Ti2 and CuTi, respectively.
(2) The homogeneity range of T, 35∼43%Cu, 29∼36%Ni and 25∼35%Ti, at room temperature is in the shape of an ellipse.
(3) The solubility of α at room temperature is about 5%Ti at 50%Cu-50%Ni, and it decreases to below 0.4%Ti in a Cu-Ti binary system.
(4) The eutectic composition and temperature of the Cu-T quasi-binary system were found to be 18%T and 1343 K.
(5) In the Cu-T quasi-binary system, α dissolves T about 10% at the eutectic temperature, and the solid solubility of α for T decreases with falling temperature to below 2%T at room temperature. On the other hand, the solubility of T for α is about 92%T at the eutectic temperature, and decreases with falling temperature to about 97%T at room temperature.View full abstractDownload PDF (818K) -
Teruo Uno, Yoshio Baba1980 Volume 44 Issue 6 Pages 624-629
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of cold work and aging on the ductility and the fracture behaviour of high purity Al-4.6%Cu alloy has been investigated to improve the low ductility of the alloy. Marked improvement in the ductility of coarse grained Al-4.6%Cu alloy can be attained by proper cold working and aging after solution treatment, and fracture mode changes from brittle grain boundary fracture to ductile transgranular fracture. These phenomena can be observed if cold work were immediately carried out after solution treatment. Preaging treatment after quenching is undesirable because of a marked decrease of ductility. The cause of the marked improvement in ductility is attributed to the absence of precipitate-free zones along grain boundaries, supression of coarse grain boundary precipitates and the precipitation of coarse intermediate precipitates (θ′ phase) in the matrix.View full abstractDownload PDF (1191K) -
Kenji Ikeuchi, Kozo Furukawa, Jin-ichi Takamura1980 Volume 44 Issue 6 Pages 630-636
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe recovery kinetics of vacancies on isothermal annealing of deformed polycrystalline gold specimens having different dislocation densities has been examined with resistivity measurement, in particular reference to the Harper form as C=C0exp(−K·tm), where C0 is the initial concentration of vacancies, t is the annealing time, and K and m are constants. The initial vacancy concentration in all specimens was kept nearly constant, regardless of amounts of strain, by introducing suitable quantities of quenched-in vacancies prior to the tensile deformation at 77 K. Main results are summarized as follows:
(1) The value of exponent m is not constant but varies with the dislocation density, obeying the relationship given by
(This article is not displayable. Please see full text pdf.)
\ oindentwhere Δρd is the resistivity increment due to dislocations introduced by the deformation, and constants a and b are 0.12 and 0.57×1011 (Ω·m)−1 for gold, respectively.
(2) In specimens having low dislocation density (tensile strain ε≤3%), the whole annealing process is described by a single exponent m. However, in specimens of high dislocation density (ε>5.5%), the early stage of annealing is expressed by an exponent m′ which is larger than m, whereas the substantial part of the annealing process is described by exponent m given as eq. (1).
(3) The effective activation energy for the annealing process is 0.70±0.02 eV regardless of the amount of strains.
The above results (1) and (2) are incompatible with the Harper’s analysis that the value of exponent m is uniquely defined by the form of the vacancy-dislocation interaction potential. Several factors accounting for the experimental results have been discussed, among which (a) vacancy flow due to the concentration gradient, (b) vacancy flow due to the vacancy-dislocation interaction force, and (c) the sink efficiency of dislocation are suggested to be most important.View full abstractDownload PDF (583K) -
Kenji Ikeuchi, Kozo Furukawa, Jin-ichi Takamura1980 Volume 44 Issue 6 Pages 637-644
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe computer simulation of vacancy annihilation to dislocations has been made by the Monte Carlo method to interpret the annealing kinetics of vacancies in deformed gold, which is described by the Harper form as C=C0exp(−K·tm), where C is the vacancy concentration, t is time, K and m are constants, as reported in the preceding paper. Three factors most important for the kinetics have been taken into account in the calculation; (a) vacancy flow due to the concentration gradient, (b) vacancy flow due to the gradient of the vacancy-dislocation interaction (elastic) potential, and (c) sink efficiency of dislocation. In the simulation, the sink efficiency has been treated in such a way that a vacancy at a nearest-neighbour site of dislocation must overcome an energy barrier ΔE on annihilation. The results are summarized as follows:
(1) In the case where dislocation acts as a perfect sink (ΔE=0), the value of exponent m in the early stage of annealing indeed ranges from 0.55 to 0.69, depending on the dislocation density, in accord with the experiment, but in the later stage approaches 1.0 in marked contrast to the experiment. The similar tendency is found even when the interaction potential is assumed to be ten times as large as the theoretically reasonable value. The present results, therefore, do not support the Harper’s analysis that the value of m is uniquely defined by the form of the vacancy-dislocation interaction potential.
(2) When a fixed sink efficiency (ΔE=const.>0) of dislocation is assumed, bearing in mind the extended dislocation, the obtained value of m becomes much higher than the experimental value, increasing with the increase in the energy barrier ΔE.
(3) A variable sink efficiency model has been found to be most appropriate, in which the energy barrier ΔE is assumed to increase with the degree of bowing-out of dislocation as a function of the number of vacancies absorbed. The exponent m in this case varies with the dislocation density in a similar way as the experimental results; for the low dislocation density the whole process of annealing can be described by a single value of m, while for the high dislocation density the annealing process consists of two stages, i.e., the early stage with the exponent m′=0.7 and the later stage with the exponent m=0.5.View full abstractDownload PDF (696K) -
Eisuke Sugimoto, Shigeki Kuwata, Zensaku Kozuka1980 Volume 44 Issue 6 Pages 644-651
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe e.m.f. method using the zirconia solid electrolyte has been applied to the study of determination of the various thermodynamic values at the temperatures above 900 K.
This work was done for the purpose of applying this method to obtain the fundamental data on practical lead refining at temperatures of 623∼773 K.
In this work, it was recognized that the stabilized zirconia was useful as an electrolyte even at the lower temperature of about 673 K and the Y2O3 stabilized zirconia was found to be better than the CaO stabilized zirconia as the solid oxide electrolyte to be used at the temperature of 673∼773 K.
For the measurement of the e.m.f. at the lower temperatures as this work, however, it must be considered to minimize the internal resistance of the cell.
E.m.f.’s of galvanic cells with the solid oxide electrolyte (ZrO2+CaO) and (ZrO2+Y2O3) were measured to determine the standard free energies of formation of PbO, FexO, Fe3O4, Cu2O and Sb2O3 in the following temperature ranges.
The cell used were as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentThe results were represented by the following equations:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (688K) -
Kanji Masui, Toshio Yamada, Yoshihiro Hisamatsu1980 Volume 44 Issue 6 Pages 651-658
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFrom a Watts-type plating bath (CoSO4-CoCl2-H3BO3) containing different amounts of phosphorous acid, Co-P alloys with compositions ranging from 0 to 14 wt%P were electrodeposited, and their structural changes at elevated temperatures were investigated by differential scanning carolimeter, X-ray diffractometer, transmission electron microscope, and small-angle X-ray scattering. Moreover, the apparent activation energy for the heat-induced structural changes in the Co-P amorphous alloys were determined by Kissinger’s method. The results are summarized as follows: (1) The deposited alloys with 0<P≤4.4 wt%, are supersaturated solid-solutions of P in the hcp Co, and those containing ∼5≤P≤14.0 wt% are amorphous solids. (2) The crystallization process of the Co-P amorphous alloys can be classified into three types depending upon the P content. The alloys with ∼5≤P<9 wt% (region I), hcp Co separates in an amorphous matrix at 550∼610 K and upon further heating the matrix transforms into stable phases of hcp Co and Co2P by eutectic crystallization at 610∼670 K. In the alloys with 9≤P<12 wt% (region II), the amorphous solids convert directly into a lamellar structure of hcp Co and Co2P by eutectic crystallization at 620∼630 K. In the alloys with 12≤P≤14 wt% (region III), Co2P separates in an amorphous matrix at 620∼630 K followed by eutectic crystallization into hcp Co and Co2P at 630∼650 K. (3) The Vicker’s hardness of the alloys increased remarkably when the amorphous matrix crystallized into the eutectic structure. For instance, the value of the Co-14.0 wt%P alloy goes up to about 1300 Hv. (4) The apparent activation energy of the structural changes in the amorphous alloys was obtained to be 215±10 kJ/mol.View full abstractDownload PDF (929K) -
Toshio Enjo, Kenji Ikeuchi, Naofumi Akikawa, Makoto Ito1980 Volume 44 Issue 6 Pages 659-665
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTi-6Al-4V alloy has been diffusion-welded in a vacuum environment with particular reference to the effect of the microstructure of base metals on the bonding process. The effect has been examined using as-received base metals (grain size of alpha phase dα=2∼3 μm), base metals annealed at 1173 K for 14.4 ks (dα≅8 μm) and base metals annealed at 1283 K for 3.6 ks (coarse plate-like alpha phase). The development of the bonding process has been evaluated from a void ratio at the bonding interface and the tensile strength of joint. The results obtained are summarized as follows. (1) The strain rate sensitivity factor m obtained from a compression test at 1123 K indicates that the as-received and 1173 K-annealed base metal deform superplastically (m=0.6), but the 1283 K-annealed base metal does not have the superplasticity (m=0.3). The strain rate increases as the microstructure of the base metal has become finer. (2) The bonding process of Ti-6Al-4V alloy is developed more rapidly in the base metal having a finer microstructure. This result is attributed to the difference in the characteristic of plastic flow between the base metals as described in (1), because the void ratio at the bonding interface and the joint strength can be described as a function of welding deformation regardless of the microstructure of base metals. (3) The diffusion welding of Ti-6Al-4V alloy (as-received) to titanium results in improvements in the void ratio and joint strength compared with that between titanium. This result suggests that the Ti-6Al-4V alloy with fine microstructure is applied successfully to the diffusion welding of titanium as an insert-metal.View full abstractDownload PDF (935K) -
Atsushi Kikuchi, Mitsuru Ayusawa, Teiriki Tadaki, Siro Maeda1980 Volume 44 Issue 6 Pages 665-671
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDeoxidation rate of liquid copper whose oxygen concentration was above 0.25 mass% was measured by employing an agitated reactor under various experimental conditions (reaction temperature=1357∼1538 K, impeller tip speed=1∼33.3 s−1, gas flow rate=2.2∼31.7 (10−6 m3(NTP)/s), mol fraction of CO in the gas phase=0.2∼1.0).
Results obtained are as follows:
(1) The resistance of mass transfer in the liquid phase is small and neglected with respect to the overall resistance of the deoxidation.
(2) The chemical reaction is the rate-controlling step at a high gas flow rate, and the rate (−r) is expressed by an equation, −r=k′pCO, where pCO is the partial pressure of CO and k′ is an apparent rate constant of the chemical reaction. The apparent activation energy and the frequency factor are 9830 J/mol and 2.7 (10−6 mol/m2·s·Pa), respectively.
(3) Both steps of mass transfer in the gas phase and the chemical reaction are rate-controlling at a low gas flow rate. An empirical correlation on mass-transfer coefficient (kG) obtained by substracting the resistance of chemical reaction from that of the over-all reaction is Sh=0.01Re2.0Sc0.5 (Sh=kGd⁄D, Re=duρ⁄μ, Sc=μ⁄ρD, d=equivalent diameter, u=gas velocity in the nozzle, ρ=density of gas, μ=viscosity of gas, and D=diffusion coefficient of the CO2-CO system).
(4) The rate of deoxidation under the experimental conditions can be estimated from the over-all rate equation and empirical equations for k′ and kG.
(5) It was pointed out that the experiments under the conditions of lower oxygen concentration and higher temperature than those of the present study are necessary to discuss the mechanism of chemical reaction.View full abstractDownload PDF (534K) -
Kazuo Kameda, Yoshio Yoshida, Senzi Sakairi1980 Volume 44 Issue 6 Pages 671-677
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe E.M.F. of the following galvanic cells involving zirconia solid electrolytes have been measured in order to obtain the standard free energy of formation of ZnO in the temperature range 818 to 986 K and the thermodynamic data of the liquid Au-Zn and Ag-Zn systems, for NZn=0.25∼0.80 and NZn=0.27∼0.85, in the temperature ranges 918 to 1123 K and 865 to 1152 K, respectively.
(This article is not displayable. Please see full text pdf.)
\ oindentThe error arising from vaporization of zinc was carefully avoided in this study.
The standard free energy of formation of ZnO was determined:
(This article is not displayable. Please see full text pdf.)
The activity curves obtained show considerably negative deviations from Raoult’s law, especially in the Au-Zn system, suggesting the large affinity of zinc for gold and silver.
The properties of alloys between metals of I B (Au, Ag, Cu, noble metals) and zinc have been discussed in terms of recent progress of the alloy theories by Engel.
It is proved phenomenologically that the break points of αZn function at approximately NZn=0.40 in liquid Au-Zn, Ag-Zn and Cu-Zn systems may be also interesting from the standpoint of recent stability theories of alloy phases.View full abstractDownload PDF (581K) -
Fumio Kurosawa, Isamu Taguchi, Mitsuru Tanino, Ryutaro Matsumoto1980 Volume 44 Issue 6 Pages 677-686
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSulfides in steels have been studied by a new non-aqueous electrolyte-potentiostatic etching method (abridged as the SPEED method). The results are summarized as follows:
(1) The SPEED method that eliminates the matrix interference may be applied to the three-dimensional observation of sulfides in steel samples including fracture surface samples and to the highly sensitive determination of light elements of sulfides, such as oxygen, nitrogen and sulfur.
(2) The SPEED method makes it possible to observe and analyze the unstable fine sulfides. In this work, MnS, Mn-S-O, TiN-MnS, Ti2S, La-Ce-O-S, Ca-Al-La-Mn-Si-Mg-S-O, Y-O-S, Y-O-S-MnS and Ca-Al-Zr-Ti-Mg-O-S are observed and analyzed. They are found to exist in steels with oxide, carbide, and nitride.
(3) A method has been proposed for a better observation and identification of FeS, (Fe, Mn)S and MnS. These sulfides are observed and identified by this method using SEM-EDX, XMA, etc. after being separated from the steel matrix by ultrasonic vibration and then collected by filtration through a metallic filter. Sulfides mentioned above are observed clearly and identified easily.View full abstractDownload PDF (2056K) -
Joo Ishihara, Masaichi Nagai, Takeo Tamamura1980 Volume 44 Issue 6 Pages 687-695
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn a previous paper, the chipping phenomena on blanking punches are described as follows: During the blanking operation, many wear pits are initiated on the side surface of the blanking punch. The side surface of the blanking punch is subjected to tensile stress and compressive stress alternately. The chipping phenomenon is initiated from fatigue cracks caused by the stress concentration at the bottom of the wear pits.
In this study, the chipping resistance of various nitrided steels for blanking punches was tested. The tested steels were age-hardening steels of the composition of Fe-3%Mn-15%Ni-V-Mo-Co, where the quantities of V, Mo and Co were varied to several levels. The steels were ion-nitrided at 723 K (450°C) for 3.6∼187.2 ks (1 to 52 h).
The results were obtained as follows:
(1) The blanking punches made of these ion-nitrided age-hardening steels are free from chipping damage.
(2) If the high-vanadium steels containing vanadium more than 3% are ion-nitrided for an excessively long time, internal cracks are initiated in the nitrided layer. But chipping does not occur during the blanking operation with these internal cracks in the nitrided layer, while slight spallings may be observed in the surface layer whithin 1.7×104 cycles.
(3) The lives of the punches made of the ion-nitrided high-vanadium steels are extremely long, if the internal cracks are not present. For instance, the life of a punch made of 3%Mn-15%Ni-3%Mo-9%Co steel which is ion-nitrided for 18 ks (5 h) at 723 K is three times longer than that of an SKD-1 steel punch, which was quenched from 1253 K (980°C) and tempered at 473 K (200°C).View full abstractDownload PDF (1494K) -
Setsuo Takaki, Youichi Tokunaga1980 Volume 44 Issue 6 Pages 696-703
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe transformation mechanism from the Mo rich zone to the high temperature precipitate and the reversion behavior of zones in Fe-18%Ni-10%Co-5%Mo alloy were investigated by means of calorimetric analysis, hardness testing and electrical resistivity measurement. Hardness changes during reheating over the temperature range 500∼575°C after preaging at 400°C for 200 h show that the amount of the maximum reversion increases with temperature differance between preaging and reheating, but that tends to be saturated. And also, the results of calorimetric analysis show that the high temperature precipitate is not formed even in the maximum reverted state. Thus, it is suggested that some of the Mo rich zones formed in preaging at low temperature stably remain during reheating at high temperature, and that these stable zones are transformed into the high temperature precipitates in that situation. In isothermal aging, the Mo rich zones formed in the early stage are considered to be stabilized in the later stage, and then transformed into the high temperature precipitates in the same way. Upon isothermal aging under 450°C, however, this transformation does not proceed at the hardening stage but occurs at the overaging stage.View full abstractDownload PDF (719K) -
Hiroh Numata, Yasuo Hira, Shiro Haruyama1980 Volume 44 Issue 6 Pages 703-711
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSElectrochemical polarization studies were made on iron, nickel and chromium in molten vanadium pentoxide, with special reference to the mechanism of vanadium attack.
Anodic polarization curves of Fe and Ni exhibited a diffusion-limiting current whereas the cathodic polarization curves seemed to be controlled by charge transfer. After several ten minutes of immersion, their surface was covered by viscous liquid film. On the other hand, the polarization current of Cr was one order of magnitude less than that of Ni and Fe, and its surface after immersion was covered by a compact solid oxide film. Instantaneous corrosion rates were estimated using the polarization resistane method which is widely used for the monitoring of corrosion rate in aquous media. The corrosion rate estimated from the method exhibited a good agreement with that obtained from weight loss. The corrosion current of Fe and Ni increased with time, corresponding to the shift in potential to negative direction. On the other hand, Cr showed a time independent corrosion rate and exhibited a constant passive potential. The results were discussed in terms of electrochemistry as well as thermodynamics.View full abstractDownload PDF (706K) -
1980 Volume 44 Issue 6 Pages 711
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPlease see pdf. Wrong:Photo. 1(A), Photo. 1(B) Right:Photo. 1(B), Photo. 1(A)View full abstractDownload PDF (741K)
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