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Volume 51, Issue 6
Displaying 1-16 of 16 articles from this issue
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Keijiro Hiraga, Keisuke Ishikawa1987 Volume 51 Issue 6 Pages 479-487
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetization-field-temperature characteristics of austenitic iron-based alloys containing Ll2 ordered phase γ′ have been investigated over the temperature range from 4.2 to 100 K in fields up to 6 MA·m−1. The alloys of Fe-(16, 18.5) Ni-16Cr-2.4Ti-1.4Mo (mass%) were used, in which the Ni concentration was lowered than that of conventional iron-based superalloys in order to decrease the magnetization of the γ phase matrix. A single-phase alloy which was an approximation of the γ phase of the 18.5Ni alloy was also used as a comparison. In the former alloys, very fine spherical γ′ phase which can be regarded as Ni3Ti containing small amount of Fe, Cr and Mo was uniformly precipitated after aging at 973 K for 86.4 ks.
An analysis of the magnetization curves revealed that the γ′ phase was ferromagnetic at low temperatures: The Curie temperature is about 60 K and the spontaneous magnetization at 0 K is 90-100 kA·m−1. For the aged alloys, the field dependence of magnetization calculated on the basis of superimposition of both the simple superparamagnetism of the γ′ particle and that of γ matrix is in a good agreement with that observed above the magnetic transition temperature of the γ-matrix of about 20 K.View full abstractDownload PDF (1452K) -
Keijiro Hiraga, Keisuke Ishikawa1987 Volume 51 Issue 6 Pages 488-495
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetic properties and austenitic phase (γ) stability at 4.2 K of γ′-strengthened iron-based alloys (γ+γ′ alloys) have been investigated as compared with those of single-phase alloys (γ alloys). The alloys containing (16-29.5)Ni-(14, 16)Cr-2.4Ti-(1-2)Mo and (11.5-20)Ni-(16-17)Cr-1.4Mo (mass%) were aged at 973 K for 172.8 ks after solutionizing at 1373 or 1423 K for 3.6 ks. Magnetization curves at 4.2 K and temperature variation of magnetization at constant fields were measured on a vibrating sample magnetometer. The amount of the a′ phase induced by cooling or 30% tensile deformation at 4.2 K was also determined by using magnetic techniques.
The differences in the properties between the γ+γ′ and γ alloys have been discussed on the basis of the magnetic transition temperature and structural parameters such as the free energy change ΔFα→γ and the Ms and Md temperatures which were calculated for the γ-matrix by using theoretical or empirical equations. It has been shown that the compositional criterion for the magnetic transition proposed by Warnes and King can be successfully applied to the γ-phase of the γ+γ′ alloys. It has been also found that the γ-phase is stabilized by the mechanical effect of the γ′ particles and solved Ti. The stabilizing effect has been estimated to be corresponding to about 330 J·mol−1 decrease in ΔFα→γ, 2.4% increase in Ni content and 140 K decrease in the Md temperature.View full abstractDownload PDF (1167K) -
Hisashi Kuwano, Kiyohiro Iioka, Yoshikazu Hamaguchi1987 Volume 51 Issue 6 Pages 496-502
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Mössbauer effect measurement has been made on an Fe-45.7 at%Cr alloy decomposed by the spinodal process at 748 K. The half width, the peak position and the shape of the internal field distribution curve were numerically analyzed on the assumption of a Gaussian distribution. The Mössbauer data are presented here in an evidence showing that the shape of the compositional fluctuation is rather close to a pulse wave then a sinusoidal one predicted by the classical spinodal theory. The amplitude of the compositional fluctuation evolves with time in four steps, in accordance with the earlier result of the Johnson-Mehl plot.View full abstractDownload PDF (917K) -
Toshihiro Seo, Kazumitsu Shinohara, Takashi Naohara1987 Volume 51 Issue 6 Pages 503-510
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMean grain sizes of σ phase particles in 25%Cr-20%Ni austenitic stainless steel have been measured during aging at temperatures between 1123 and 1223 K in order to make theoretical analyses of the growth kinetics of the grains. It has been found that both of the γ and σ phases follow the fourth powered law as described below:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere R, R0, K and t are, respectively, a mean radius of the grains at time, t, an initial radius at time=0, a growth constant and an aging time. The growth constant is, however, different between the growing phases, γ and σ, as follows:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere K′s are, respectively, the growth constants for superscripted phases, and β is the Zener parameter and f the volume fraction of the σ phase. Furthermore, the growth of the σ phase has been found to be controlled by the diffusion along the grain boundaries between precipitates and matrix, i.e., by the mechanisms of Ostwald ripening. The growth of the γ phase has taken place under the influence of pinning action by the precipitated σ particles: The driving force to grow grains of the γ phase has been supposed to be approximately equal to one-sixth of that to grow the σ particles.View full abstractDownload PDF (1947K) -
Masaru Yokota, Yoji Fujita, Keiichiro Shoji1987 Volume 51 Issue 6 Pages 511-517
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSConcentration distribution curves (c-x curves) for interdiffusion in complete solid solution of copper-nickel and iron-nickel binary alloy systems were obtained by the following three methods: (1) Experiment by using EPMA, (2) analytical computation based on a concentration independent interdiffusion coefficient (\ ildeDConst.) and (3) approximate computation based on a concentration dependent interdiffusion coefficient (\ ildeD(c)) by the use of the finite element method.
The experimentally determined c-x curves were compared with two types of computed ones. Then the usefulness of a method of determining the degree of homogenization (interdiffusion or sintering) was discussed. The results were as follows:
(1) The computed c-x curve on the assumption of \ ildeD(c) was consistent with the experimentally obtained one, but the c-x curve on the assumption of \ ildeDConst. was not exactly consistent with the experimentally obtained one, especially at the points dc⁄dx=0 and d2c⁄dx2=0 on the c-x curves, corresponding to the center of a foil composing the diffusion couple and the vicinity of joined interface, respectively.
(2) The degree of homogenization (interdiffusion), H, computed on the assumption of \ ildeD(c) agreed with the graphically obtained value, but that on the assumption of \ ildeDConst. deviated slightly from the graphically obtained valus.
By the use of experimental data on \ ildeDConst. in an alloy system, H value at any time can be estimated roughly. To obtain the exact H value, \ ildeD(c) should be taken into consideration in computation.View full abstractDownload PDF (1147K) -
Hidekazu Sueyoshi, Katsuro Suenaga, Ryohei Tanaka1987 Volume 51 Issue 6 Pages 518-524
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn influence of the austenitizing treatment followed by slow cooling on the graphitization in hypo-eutectoid alloy steels has been studied. The number of graphite nodules and the rate of graphitization remarkably depend on the austenitizing conditions. The rate of graphitization increases with an increase in graphite nodule number. From both the above mentioned result and the fact that the growth rate of graphite is independent of the austenitizing conditions, it is suggested that the austenitizing conditions have a major influence on the nucleation of graphite.
In the pre-treatment that a steel is held at the austenitizing temperatures, until traces of cementite disappear completely, and then slow-cooled to room temperature, the graphitization is most greatly stimulated. Cementite in pearlite formed after the above mentioned pre-treatment was found to be fine lamellae. It is concluded that fine cementite is unstable because of larger surface energy and may cause an easy nucleation of graphite thereby.View full abstractDownload PDF (1573K) -
Akira Kawasaki, Ryuzo Watanabe1987 Volume 51 Issue 6 Pages 525-529
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of interlayers having controlled compositional gradients on the residual thermal stress distributions of stainless steel/silicon nitride and tungsten/zirconia bondings was studied by the finite element method. A cylindrical model for the sample geometry and stepwise compositional variations in the interlayers were employed for the calculation. The thermal stress distributions were determined under the condition of a temperature difference of 1400 degrees using the elastic constants and the thermal expansion coefficients of the materials involved, assuming their linear dependence on the composition of the interlayer. Marked effect of reducing the thermal stress of the metal/ceramic bonding has been expected by inserting the interlayers with stepwise compositional profiles. The effect of width and compositional graduation fineness, as well as the composition profile, of the interlayers on thermal stress reduction has been demonstrated.View full abstractDownload PDF (655K) -
Motohiro Kanno, Noriaki Shimodaira1987 Volume 51 Issue 6 Pages 530-535
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn a previous paper, it has been shown that ductility of a Cu-4.4 mol%Sn alloy being poor at temperatures above about 573 K is markedly increased above 973 K by a small amount of additional boron and magnesium. In this experiment, hot ductility of the alloy affected by additional elements such as yttrium, cerium, lanthanum and calcium of about 0.1 mol% was further investigated in comparison with that of the alloy with and without additional boron. It was made clear that the ductility at temperatures above 973 K was improved to a great extent by the addition of yttrium, cerium and lanthanum. The ductility improvement was regarded to be due to an increase in grain boundary strength probably caused by inhibition of preferential oxidation of grain boundaries by these additional elements in the same way as caused by additional boron. On the other hand, an intermediate temperature embrittlement appearing around 673 K which was accompanied by intergranular fracture in the alloy with and without additional boron was much alleviated by the addition of yttrium, cerium, lanthanum and calcium. Auger electron spectroscopy revealed that a trace impurity of sulfur segregated in grain boundaries of the alloy. Sulfides containing yttrium were found to disperse in the matrix of an yttrium-bearing alloy, but no sulfides in a boron-bearing alloy. Thus, the alleviation of the intermediate temperature embrittlement caused by the additional elements was attributed to the increase in grain boundary strength due to desulfurization.View full abstractDownload PDF (1781K) -
Mitsuo Asawa1987 Volume 51 Issue 6 Pages 536-542
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBehavior of stressed Type 304 steel in H2SO4 solutions with addition of cyanide or thiocyanate has been studied in view of the reported strong adsorption characteristics of the latter spiecies and their tendency to cause embrittlement in carbon steel. Type 304 wire annealed was examined at 353 K in 1 to 4 kmol/m3 H2SO4 solutions with additions of different quantities of KCN, NH4SCN, or NaN3(pseudohalides) mainly under open circuit conditions at a stress of 275 MPa.
With increased additions of KCN or NH4SCN the attack morphology changed from heavy general corrosion to cracking or localized attack and the time-to-failure was prolonged. This is similar to a previously reported behavior of Type 304 in H2SO4 solutions with halide. KCN was a cathodic and anodic inhibitor and NH4SCN was a cathodic inhibitor. The latter was also an anodic inhibitor at and near the open circuit potential. H2S gas evolution from the solution containing NH4SCN was detected suggesting the role of hydrogen in cracking mechanism, as in the case of KCN. In the solutions containing NaN3 Type 304 did not fail due to passivation resulting from the cathodic reaction stimulated by NaN3 or failed by general corrosion at the small additions of NaN3.View full abstractDownload PDF (1494K) -
Yoshiaki Iguchi, Sumio Yamashita, Michio Inouye1987 Volume 51 Issue 6 Pages 543-547
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to study the wetting between solid iron and liquid slag in the softening and the melting zone in iron blast furnaces, the contact angles of sessile drops of CaO-SiO2, CaO-SiO2-Al2O3 and CaO-SiO2-MgO liquid slags on solid iron plates were measured in CO-CO2 gas mixtures at 1723 K. The following results were obtained. (1) The contact angle increases with the increase in basicity of slags from 0.5 to 1.0 under the same oxygen partial pressure. The addition of Al2O3 and MgO has no significant effect. (2) The contact angle decreases gradually with the increase in FeO content, independently of the kind of those slags. (3) The liquid slags containing FeO more then 30 mol% perfectly wet the surface of solid iron.View full abstractDownload PDF (776K) -
Nobuyuki Morito, Shinji Kobayashi, Tohru Sato, Toshiko Suzuki1987 Volume 51 Issue 6 Pages 548-552
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOn the free surface side of amorphous alloy ribbons which were made by the single roller process, the formation of round and small humps is observed occasionally. The nucleation frequency of small humps increases as defects at the corner of a slit orifice become larger. According to the computer simulation of casting and solidification process in the single roller method, a big turbulence in the melt flow has been found out on the free surface side at the same time as molten metal stream is ejected from a nozzle slit. If there are some defects at the corner of the slit orifice, they must result in a remarkable turbulence in the flow of molten alloy and big waves on molten surface. Then gas in surrounding atmosphere is taken in as voids on the free surface side at the time of the solidification on a rapidly moving substrate surface to form many small humps.
This suggestion was supported by the presence of hydrogen and oxygen as gas in voids that was detected by means of secondary ion mass analysis.View full abstractDownload PDF (923K) -
Ryohei Satoh, Muneo Ohshima, Kazuo Hirota, lchiro Ishi1987 Volume 51 Issue 6 Pages 553-560
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA high reliable solder bonding method called Self-streching Soldering Technology (SST) has been developed to realize high density packaging for electoronics circuits.
As micro-solder bonding of IC·LSI undergos thermal stress caused by the thermal expansion differene between the chip and the substrate during the use, a lower thermal stress bonding method is demanded for high density packaging.
In order to find and realize the low thermal stress solder shape, structure analyses by Finite Element Method (FEM) and control method of solder shape were investigated.
Results obtained are as follows;
(1) The waist bonding shape was found to be a low stress structure under constant solder volume, according to FEM simulation.
(2) The waist shape of joint solder could be controlled by the balance of upper and lower directional force causing the surface tension of molten joint and control solder.
(3) The molten solder shape and control balance equation could be conducted by Laplace-Young theory.View full abstractDownload PDF (1980K) -
Takehiko Itagaki, Toshiharu Kobayashi, Takashi Arai1987 Volume 51 Issue 6 Pages 561-568
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain information on the degradation of strength of tungsten fiber in tungsten-fiber-reinforced superalloys, several types of tungsten wires were nickel-plated and held at high temperatures, and then changes in microstructures were observed. The wires employed were those of ordinary-lamp-grade doped tungsten, halogen-lamp-grade doped tungsten, W-3%Re, W-2%ThO2 and W-2%Y2O3. They were made by powder metallurgy processes and cold-drawn to 1 mm diameter.
Recrystallization was not observed in plain wires after annealing at 1523 K for 10.8 Ms (3000 h). However, recrystallization occurred in all the wires during annealing even at the lower temperature of 1273 K when nickel was deposited on them. In most cases the recrystallization was found to be preceded by an incubation time, during which diffusion of nickel seemed to proceed inwards from surface of the wire. The extent of recrystallization varied with the kind of alloys and the annealing temperature. At 1373 K the order of ease of recrystallization was W-2%Y2O3, W-2%ThO2, W-3%Re and the two doped tungstens, and at 1573 K it was W-2%ThO2, halogen-lamp-grade doped tungsten, ordinary-lamp-grade doped tungsten W-2%Y2O3 and W-3%Re. The order of degradation of the high temperature strength for the wires annealed at 1573 K almost agreed with the order of ease of recrystallization at the same temperature.View full abstractDownload PDF (2850K) -
Taichi Kamijo, Hiroshi Fukutomi, Satoshi Ogino, Toshikazu Shimizu1987 Volume 51 Issue 6 Pages 569-576
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt has so far been reported that an addition of a small amount of tin makes it possible to omit the solution treatment for the aging of Cu-Cr alloy; i.e. the aging of Cu-Cr-Sn alloy water sprayed after hot rolling causes an increase in hardness comparable with the normal heat treatment. In the present work the effect of 0.16 mass%Sn addition on the age hardening kinetics in a Cu-0.6 mass%Cr alloy was studied using a heat treatment keeping specimens at 1123 K at different exposure times, so as to vary the solute chromium content prior to the aging.
Under a low supersaturated condition nucleation of homogeneous precipitation hardly occurred by aging at 723 K. While, the precipitation of chromium took place on the surface of the dispersed particles formed during hot-rolling, scarcely resulting in any increase in hardness. When the alloy was aged after cold-rolling at the same temperature, a noticeable increase in hardness was observed in the alloy containing tin by inhomogeneous precipitation on dislocations. The contribution to age hardening of work hardening due to the retained deformed matrix was clearly seen. The greater the amount of chromium content dissolved in the matrix after hot-rolling, the higher the increase in hardness after the aging. Retardation of recovery and recrystallization, which greatly affects age hardening, was attributed to the pinning effect of fine precipitates on climbing of dislocations. The addition of a small amount of tin not only retarded the precipitation of chromium occurring during hot-rolling, but also prevented the recovery pocess by means of segregation of tin to dislocations. Thus, the addition of tin to Cu-Cr alloy contributed simultaneously to the increase in precipitation hardening and improvement of heat resistance.View full abstractDownload PDF (2590K) -
Takakazu Suzuki, Hiroyuki Umehara1987 Volume 51 Issue 6 Pages 577-583
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermal deposition of Al on high modulus pitch-base carbon fiber tows from the tri-iso-butyl aluminum has been studied. The method carried out in the range from 523 to 673 K seems to be superior to other methods, for example, vacuum evaporation, sputtered deposition or electrodeposition and so on, from the view of throwing power, which is the penetrability of the source into the middle of the tows. The purpose of this study is to coat the fiber with Al uniformly and minutely without degradating the fiber and to provide a preform of carbon fiber-Al composites.
In this paper, we have described the effects of the vaporization temperature of the source (Tv) and the deposition temperature (Td) on the microstructure of the deposited aluminum. Moreover, the degradation of the fiber by the process has been estimated. In the experiment the total gas pressure (Pt) and the gas flow rate of Ar and isobutylene gas have been kept at 1333 Pa and a constant, respectively.
As a result, the optimum Tv has been between 333 K and 363 K. Then the pretty white silver Al deposits have been obtained at the Td from 533 K to 583 K. But at 603 K and above, the color of the deposits has become darker slightly. In the deposits relatively larger amounts of carbon and oxygen have been contained. The optimum Td has seemed to be below 583 K.
From the tensile testing, we have estimated the degradation of the coated fibers; non-coated fibers and Al deposited ones have given almost the same strength. Hence it has been obvious that the coated fibers have never been weaken by this CVD process.View full abstractDownload PDF (1348K) -
Hakaru Masumoto, Masakatsu Hinai, Showhachi Sawaya1987 Volume 51 Issue 6 Pages 584-590
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe damping capacity, magnetic and mechanical properties and corrosion resistance have been investigated in Fe-Co-Mo-Cr alloys. The internal friction and magnetic hysteresis measurements, and the tensile test were carried out by using an inverted torsion pendulum, an automatic recording fluxmeter and an Instron-type machine, respectively. The anodic polarization characteristics in 3%NaCl and 5%H2SO4 solutions were measured by a potentiostat method.
The maximum internal friction Qmax−1 depends largely on the change in magnetic properties with alloy composition and heat treatment. In the case of Fe-Co-Mo-Cr alloys containing 20%Cr, fairly high values of Qmax−1 greater than 50×10−3 are obtained upon furnace cooling in the composition range of 2-4%Co and less than 2.5%Mo, and in the composition range of less than 6.5%Co and less than 9.5%Mo upon water quenching.
The Fe-Co-Mo-Cr alloys with high values of Qmax−1 show a microstructure of α single phase and have a moderately small Hc, whereas those with very low values of Qmax−1 show a two-phase microstructure and have very large Hc. Therefore, the larger the magnetic hysteresis loss at a small strain amplitude, the higher the Qmax−1 value becomes.
The tensile strength and the yield strength of the alloys with 4%Co and 20%Cr increase with increasing Mo concentration, but the elongation decreases. The pitting and sulfuric acid corrosion resistances are improved with the increase in Mo concentration, because the pitting potential in NaCl solution increases sharply and the critical current density in H2SO4 solution decreases rapidly.View full abstractDownload PDF (945K)
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