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Volume 50, Issue 1
Displaying 1-17 of 17 articles from this issue
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Tsunehiko Todoroki, Hirokazu Tamura1986 Volume 50 Issue 1 Pages 1-10
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThree types of phases, the CsCl(B2) type, the rhombohedral (R) type and the monoclinic (M) type, are recognized in near-equiatomic Ti-Ni alloys. The effect of the heat treatment (633 K-933 K) after cold work on the phase transformations among these three phases in three Ti-Ni alloys (49.7, 50.2 and 50.6 at%Ni) has been investigated by D.S.C. measurement.
The results are summarized as follows:
(1) The phase transformations are classified into the following three types according to the heat treatment temperature; (a) B2→R→M during cooling and M→R→B2 during heating for lower heat treatment temperatures; (b) B2→R→M during cooling and M→B2 during heating for intermediate heat treatment temperatures; and (c) B2→M during cooling and M→B2 during heating for higher heat treatment temperatures.
(2) The more the Ni content increases, the larger the temperature range for the R-phase to exist becomes and the more the R-phase transformation temperature decreases with the increase of the heat treatment temperature. But the R-phase transformation of the alloys heat-treated at 633 K starts at about 330 K, which is almost independent of the Ni content.View full abstractDownload PDF (1360K) -
Kei Ameyama, Tadashi Maki, Imao Tamura1986 Volume 50 Issue 1 Pages 10-19
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe morphology and crystallographic feature of austenite (γ) precipitated from ferrite (α) grain during aging in the (α+γ) two phase region have been investigated using Fe-25%Cr-7%Ni-3%Mo and Fe-25%Cr-6%Ni (α+γ) two phase stainless steels.
The starting structure of the steels before aging was fully ferritic. The precipitation process of γ from α was found as follows: (1) precipitation of fine γ allotriomorphs at α grain boundary, (2) formation of filmed γ along α grain boundary by coalescence of the γ allotriomorphs, (3) growth of spiked γ from the filmed γ into α grain, and (4) intragranular precipitation of γ particles in α grain.
The intragranular precipitated γ shows rod-like shape with the growth direction of ⟨111⟩α. Among rod-like γ, twinned γ pairs were frequently observed. Each γ of the pair was found to hold not only Kurdjumov-Sachs (K-S) orientation relationship against α matrix but also twin relation to the other γ of the pair at the same time. There is only one K-S variant allowed for the formation of twinned γ pairs to satisfy the above two conditions. The twinned γ pairs also frequently change to be pipe-shaped in a later growth stage, because of loccal dilution of Ni atoms in α near a concave surface of the γ pairs.View full abstractDownload PDF (3142K) -
Toshio Enjo, Toshio Kuroda1986 Volume 50 Issue 1 Pages 20-27
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffect of the microstructure on the hydride precipitation behavior has been studied on a Ti-6Al-4V alloy cathodically charged at various current densities using internal friction measurement and transmission electron microscopy.
The hydride precipitation by cathodic charging was observed not only near the surface but also inside the specimen for the β annealed specimen consisting of α+β microstructure. The hydride precipitation was observed only near the surface of the specimen for the β quenched specimen of α′ microstructure, and for the α+β quenched specimen consisting of α+α′ microstructure. The γ hydride phase precipitated at the α⁄β interface and inside the α and β phases for the β annealed specimen. The γ phase also precipitated at the α⁄β or α′⁄α interface and inside the α′ phase for the α+β quenched specimen.
An internal friction peak appearing at 190-220 K by using 1 Hz was related to hydride precipitation. The peak height increased with increasing cathodic charging time.
The precipitation of hydrides caused the Bordoni peak related to the strain of α phase matrix. The peak at 220-280 K at 1 Hz appeared only with the presence of a large amount of hydrogen and strain, and the peak was considered to be due to the interaction of dislocation with hydrogen.
The Bordoni peak and the peak at 220-280 K at 1 Hz appeared clearly for the α+β quenched specimen and the β quenched specimen. However, their peaks were difficult to occur for the β annealed specimen, because of the presence of β phase.View full abstractDownload PDF (2612K) -
Keisuke Ishikawa, Toshio Ogata1986 Volume 50 Issue 1 Pages 28-33
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTensile test was carried out on four alloys at liqud helium temperature to study the effect of strain rate on the deformation behavior. Alloys used were Fe-13%Ni alloys, SUS 304L, SUS 310S and 5083-O aluminum alloys, which were fully ductile even at liquid helium temperature.
At lower strain rate serrated flow was observed for every alloy, and at higher rate all flow curves became smooth. Proof stress has little strain rate dependence, but tensile stress decreases with an increase in strain rate. The latter fact would be associated with adiabatic deformation, which depends upon the thermal properties of the alloys at low temperatures.View full abstractDownload PDF (701K) -
Tomei Hatayama, Takuji Okabe, Hideo Takei1986 Volume 50 Issue 1 Pages 34-39
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe strain rate sensitivity index, m, of Al-33Cu and Al-27Cu-5Si alloys was measured by the two methods, (a) the differential closs-head speed method and (b) the strain rate change method. The m-value by the method (a) was dependent strongly on strain and decreased with increasing strain. The m-value by the method (b) was dependent slightly on strain, but strongly on the width and the sense of the change from a given strain rate, \dotε1, to another one, \dotε2. The dependence of m on the width, J∗=∂m⁄∂\sqrt(lnN)2 where N=\dotε2⁄\dotε1, was positive or negative depending on whether the strain rate was lower or higher than the strain rate having the maximum m-value on the m-ln\dotε curve when N=2 (the reference curve of m). At the strain rate having the maximum m-value, the value of |J∗| showed the minimum value (|J∗|∼0). Since the m-value is defined by the strain rate and strain rate change, it is desirable to measure m by the method which excludes the effect of strain on flow stress, and it is suggested that the strain rate change method is the one in accordance with the definition. When specimens were deformed under the condition of the same m-value on the reference curve of m, the fracture strain and the uniformity of deformation in the strain rate region where J∗>0 were higher than those in the region where J∗<0.View full abstractDownload PDF (866K) -
Masayuki Yoshiba, Ohmi Miyagawa, Hiroyuki Mizuno, Hiroshi Fujishiro1986 Volume 50 Issue 1 Pages 40-49
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to investigate the effect of environmental factors such as the corrosive species and temperature on the creep rupture properties of a nickel-base superalloy subjected to hot corrosion, creep rupture tests have been performed of Inconel 751 specimens with and without coating of different compositions of Na2SO4-NaCl salt mixtures in a temperature range between 1023 and 1173 K. The effect of hot corrosive environment on the creep rupture strength and the rupture behavior was found to differ considerably, depending on temperature and salt composition. Adding only a small amount of NaCl to the coating salts results in the marked degradation of the creep rupture strength along with the completely altered rupture behavior as compared with the case in air, in which the stress-enhanced preferential intergranular penetration of sulfides, oxides and occasionally chlorides causes directly a premature intergranular fracture in a brittle manner prior to the formation of creep-induced internal grain boundary cracks. In particular, the detrimental effect of NaCl bearing environment is more pronounced in the lower temperature region below about 1073 K, even if it is lower than the melting point of salt, where chromium oxy-chlorides play the most important role in the intergranular attack behavior. However, an aggressive intergranular attack associated with the oxy-chloride formation tends to decline with increasing temperature because of higher volatility of oxy-chlorides as well as NaCl. In the higher temperature region above about 1073 K, an intergranular attack proceeds mainly by a successive sulfidation-oxidation process, while NaCl appears to play a catalystic action to promote the Na2SO4- induced aggressive attack. Further increased temperature to about 1173 K results in the rather mitigated degradation of corrosion rupture properties along with the rupture behavior essentially similar to that in air because of the oxidation-dominating intergranular attack.View full abstractDownload PDF (3667K) -
Masuo Hagiwara, Yoshinari Kaieda, Yoshikuni Kawabe1986 Volume 50 Issue 1 Pages 50-56
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of post-consolidation heat treatment on the microstructure and the resultant mechanical properties were evaluated both at room and cryogenic temperatures (77 K and 4 K) for hot isostatically pressed (HIP) Ti-6Al-6V-2Sn alloy powders made by the rotating electrode process (REP).
The uniform, high integrity properties equivalent to wrought mill annealed material were obtained by this fabrication method.
The post-consolidation heat treatment had a marked effect on the microstructural modification. The highest ductility was obtained for as-HIP fabricated and mill annealed materials. The solution treated and aged (STA) material showed the highest strength with moderate ductility, whereas the beta annealed materials exhibited the lowest strength and ductility. The fracture toughness showed the highest value in the as-HIP fabricated condition, and the lowest in the STA condition. The good properties combinations obtained in the as-HIP fabricated condition could be attributable to the formation of finer and lower aspect ratio alpha platelets during alpha-beta HIP treatment.
The comparison with HIP consolidated REP Ti-6Al-4V alloy powders showed that strength was somewhat higher for Ti-6Al-6V-2Sn, whereas ductility was higher for Ti-6Al-4V, especially at cryogenic temperatures.View full abstractDownload PDF (2900K) -
Haruo Nozaki, Yuji Uesugi, Yukio Nishikawa, Imao Tamura1986 Volume 50 Issue 1 Pages 56-63
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMany models were suggested for the phase transformation superplasticity. Most of them provide only qualitative pictures of the mechanism. The internal stress theory by Greenwood et al. gives a quantitative explanation of experimental results, but neglects the compatibility of strain and the balance of stress. In the present study, we proposed the equation between transformation plastic strain εtp, and applied stress by using continuum mechanics which satisfied the conditions above mentioned. Main results obtained are as follows.
(1) The equation proposed shows a qualitative good agreement with experimental results that εtp, increases linearly in the range of low applied stress σA and rapidly in the range of high σA, and that εtp increases as \dotT decreases. This suggests that the deformation during phase transformation approaches the normal creep, since the contribution of internal stress decreases relatively in the condition of high σA or low \dotT.
(2) The eigen strain due to volume chance in a newly transformed region arrises to relieve the applied stress σA and creates internal stress. The matrix is deformed plastically by internal stress and σA. It seems that the internal stress decreases soon due to mechanisms proposed up to present, for instance, stress relaxation by plastic deformation. It is, therfore, suggested that the phase transformation superplasticity results from the repeating occurrence and decrease of internal stress.View full abstractDownload PDF (1039K) -
Kusuhiro Mukai, Tsutomu Harada, Tetsuo Nakano, Keisuke Hiragushi1986 Volume 50 Issue 1 Pages 63-71
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExperiments show the following facts: Local corrosion of solid silica at the surface of liquid PbO-SiO2 slag progresses in the area where the slag film, creeping up along the surface of the solid silica from bulk slag, moves actively by the Marangoni effect. Oxygen in the atmosphere does not affect the local corrosion. The local corrosion does not occur for the silica specimen which is wound tightly with platinum wire at the slag surface. The wire prevents the slag film from moving. Leading part of the local corrosion is in the portion where the specimen is washed vigorously with thin stag film which is rising up from the bulk slag. In this portion, the corrosion rate increases with increasing the film velocity.
The corrosion rate in the leading part is well described by the rate equation derived from the assumption that the rate is controlled by mass transport of dissolved SiO2 in the slag film under the Marangoni flow of the film. The assumption is supported by the experiment made of the dissolution rate of rotating SiO2 cylinder into the bulk slag.
The above results confirm that neither the volatile component in the slag nor oxygen in the atmosphere causes the local corrosion and the local corrosion results from the effective promotion of mass transport of the dissolved component from the specimen by the active Marangoni flow in the diffusion layer in the film.View full abstractDownload PDF (1234K) -
Kiyoshi Terayama, Masao Ikeda1986 Volume 50 Issue 1 Pages 71-76
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present study is concerned with the kinetics of carbon reduction of CoO and CoFe2O4 by the effluent gas analysis method. The results are as follows:
(1) The reduction of CoO starts at about 1163 K, and the activation energy is calculated to be 236 kJ/mol.
(2) At an earlier stage of reduction of CoFe2O4, the reduction of CoO in CoFe2O4 occurs to yield metallic cobalt. The activation energy of 243.6 kJ/mol nearly equal to that for the Boudouard’s reaction is obtained.
(3) The clear observation and analysis of the reduction product of CoFe2O4 are successfully conducted by the non-aqueous electrolyte-potentiostatic etching method (abridged as SPEED method). In addition, X-ray diffraction and EPMA examination are also used to identify the phases formed.View full abstractDownload PDF (1554K) -
Kazuichi Mizoguchi, Masahiro Yamane, Yukio Suginohara1986 Volume 50 Issue 1 Pages 76-82
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe viscosities of CaO, MgO and Na2O-SiO2 systems containing Ga2O3 were measured and an ionic form of Ga3+ ions was discussed on the basis of the effect of Ga2O3 on the viscosities of the melts. For example, the viscosity changes with increasing additions of Ga2O3 in Na2O-SiO2 melts were almost same as those of Al2O3 in CaO-SiO2 melts. The results indicate that Ga2O3 plays as an amphoteric oxide as Al2O3 in silicate melts. The viscosities measured in this study were well arranged and the ratio of the number of tetrahedrally coordinated Ga3+ ions to that of total Ga3+ ions could be calculated using a following parameter (Pη) which corresponds to the ratio of nO0⁄nSi in the binary silicate melts.
The parameter Pη is expressed by
(This article is not displayable. Please see full text pdf.)
\ oindentwhere ZMe is the electric charge of Me ion, ni is the ion fraction of i ion and XGa, is the ratio of tetrahedrally coordinated Ga3+ ions to total Ga3+ ions.
The XGa values of CaO, MgO and Na2O systems were calculated as 0.481, 0.341 and 0.666 respectively. It is considered that the difference in these values between each system is due to the basicity of the basic oxides consisting of the silicate melts. Ga2O3 is founded to play as more basic oxide than Al2O3 since the values of XGa in this study have about 70% of those of XAl obtained in the same silicate systems.View full abstractDownload PDF (913K) -
Yong Hack Lee, Kimio Itagaki1986 Volume 50 Issue 1 Pages 83-89
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe heat contents of the Sb-S and Sb2S3-FeS systems were measured by a drop-calorimeter in the concentration ranges of NS=0 to 0.6 and NFeS=0 to 1, and in the temperature ranges of 750 to 1350 K and 750 to 1500 K, respectively.
The method of quantitative thermal analysis was applied to calculation of the thermodynamic quantities such as the activity of the components and the heat and entropy of mixing in the liquid Sb-S and Sb2S3-FeS systems. A considerably large positive deviation from a Raoultian behaviour was observed in aSb of the Sb-S system at 1300 K, while the sulfur pressure increased drastically at about NS=0.6 where the compound Sb2S3 is located. Large positive deviations from Raoultian behaviours were also observed in aSb2S3 and aFeS of the Sb2S3-FeS system at 1473 K in the high concentration range FeS above NFeS=0.7.View full abstractDownload PDF (899K) -
Fumio Kurosawa, Isamu Taguchi1986 Volume 50 Issue 1 Pages 89-97
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe precipitation behavior of phosphides which are the most important compounds in the centerline segregation zone of continuously cast (CC) steel slabs has been studied using the non-aqueous electrolyte-potentiostatic etching method (the SPEED method).
The results are summarized as follows.
(1) Iron phosphides were clearly observed in middle (0.16%C or more) and high carbon steel slabs as spheroidized eutectic compounds, but not observed in low carbon steels.
The spheroidized eutectic phosphides were identified as (Fe, Mn)3P, (Fe, Mn)2P and steadite (Fe3P-Fe3C-Fe).
(2) The precipitation zone of the eutectic phosphides depends on the C and P contents of CC slabs, and the phosphide precipitates in slabs of about 0.16%C or more. Thus it is considered that the precipitation of the spheroidized eutectic phosphides depends on the primary austenite (γ) at solidification of CC slabs, and an increase in the γ quantity causes the solubility of P in the γ to drop. Therefore, the P segregates along γ grain boundaries, and then concentrates spheroidized and precipitates as the eutectic phosphides.
(3) The morphology and composition of the spheroidized eutectic phosphide, (Fe, Mn)3P, change into those of (Fe, Mn)2P and FeP by heating at about 1173 K.
(4) The precipitation zone of the phosphides is in good agreement with both the weld cracking zone and the poor ductility zone concerning hot ductility in carbon steels.
Thus it is considered that the embrittlement owing to phosphorus is caused by the phosphides with low melting point.View full abstractDownload PDF (4512K) -
Tetsuyuki Ikeda, Seiki Nishi, Takashi Yagi1986 Volume 50 Issue 1 Pages 98-107
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAl-8%Pb alloy ingots 20 to 40×10−3 m in diameter and 180×10−3 m in height were cast in a movable metal mold with water spraying at mold moving speed of 0.5 to 3.0×10−3 m/s at a casting temperature of 1273 K. Cooling rate and temperature gradient of these ingots within a temperature range in which two liquid phases coexist were 2.5 to 15.5 K/s and 5 to 4.5×103 K/m respectively and rate of monotectic solidification was 500 to 4500 μm/s. When cooling and solidification modes were the intermediate type between solidification by water dipping and unidirectional soliclification, gravity segregation was reduced in these ingots. This solidification mode is to cool the liquid phase from the side wall of a metal mold and to cool unidirectionally by a solidified layer beneath it. Based on this cooling mode, the homogeneous ingot could be produced according to the solidification mode which solidify steadily in the vertical unidirection into a L1+L2 region with high heat gradient. The casting condition was 40×10−3 m in diameter, 1.0×10−3 m/s in mold moving speed and 1273 K in casting temperature.View full abstractDownload PDF (1829K) -
Noboru Yoshikawa, Hajime Suto1986 Volume 50 Issue 1 Pages 108-113
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe behavior of tetragonal (t)-monoclinic (m) transformation in partially stabilized zirconia (PSZ) containing yttria from 0 to 6 mol% was investigated by means of dilatometry. The results are as follows:
(1) The transformation temperature (T0m−t) decreases lineally with increasing Y2O3 content. The present data almost coincide with the result by Ruh et al..
(2) By using the relationship between T0m−t and Y2O3 mol% as a conversion curve, the equilibrium concentration of t-phase in alloys annealed at 1600°C (1873 K), 1700°C (1973 K) and 1800°C (2073 K) was determined from their T0m−t, and it was found that the solubility limit of Y2O3 in t-phase increased with rising temperature.
(3) The as-annealed PSZ was composed of (t+c) phases, but the m\ ightleftharpoonst transformation took place more and more easily by cyclic heating. These transformations can proceed isothermally with release of the transformation-induced internal stress by the aid of slow speed cracking.
(4) The t\ ightharpoonupm transformation is suppressed by rapid cooling, but the m\ ightharpoonupt transformation is not much affected by the heating rate.View full abstractDownload PDF (1343K) -
Noboru Yoshikawa, Hiroyuki Eda, Hajime Suto1986 Volume 50 Issue 1 Pages 113-118
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to re-examine the the phase diagram of ZrO2-Y2O3 system, well-prepared ZrO2-Y2O3 co-precipitation powders were sintered, annealed at 1600°C (1873 K), 1700°C (1973 K) and 1800°C (2073 K), and then the conjugate compositions of tetragonal (t) and cubic (c) phase grains were analysed by means of EPMA. The present data of t-phase coincided with those by dilatometry reported in our previous paper. These data do not contradict X-ray data by Ruh et al., but it is considered that the solubility line of t-phase should be drawn in a different way from them. The anomalous shape of solubility line is discussed from the viewpoint of tetragonality and the abnormal t-c transformation of ZrO2.View full abstractDownload PDF (2355K) -
Keiichi Kuniya, Hideo Arakawa, Takashi Namekawa1986 Volume 50 Issue 1 Pages 119-125
Published: 1986
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of fiber arrangements and additional elements on reciprocating sliding wear characteristics of copper-carbon fiber composite was studied. Results obtained in this study were as follows:
(1) The wear volume of the copper-carbon fiber composite appeared to be smaller than that of copper alloys.
(2) The wear volume of the copper-carbon fiber composite became larger, as the sliding load increased and the volume fraction of carbon fiber increased beyond 30 volume percent.
(3) The effectiveness of fiber arrangement in reducing the wear volume was the highest in the random arrangement, medium in the direction perpendicular to the unidirectional fiber direction and the lowest in this fiber direction.
(4) The wear volume of the composite was decreased by the addition of Sn and Zr. However, the addition of these elements could not achieve the isotropic wear characteristics of the composite.
(5) It was found that the isotropic wear characteristics of the composite could be obtained by the addition of carbon powder. The isotropic wear characteristics and the reducing wear volume of the composite could be attained by the addition of Zr and carbon powder together.View full abstractDownload PDF (1723K)
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