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Volume 34, Issue 1
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Masahiro Kitada, Toshio Doi, Tadashi Umezawa1970 Volume 34 Issue 1 Pages 1-5
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAnisotropies in the H-Jc characteristics of the rolled Nb-40Zr-10Ti alloy sheets were investigated. H-Jc characteristic of various heat-treated specimens were measured at 4.2°K in a transverse magnetic field.
The results are as follows:
(1) When the rolled plane is parallel to the applied magnetic field, the critical current density is 1.7×105 A/cm2 at 60 kOe. In case the rolled plane is normal to the applied magnetic field, however, the critical current density decreases to about 1/3 to 1/6 of the above value.
(2) The most suitable treatment to increase the critical current density of the specimens is the intermediate heat treatment at 700°C for 1 to 5 hr.
(3) When the rolled plane is fixed parallel to the applied magnetic field and only the angle of the rolling direction to the applied magnetic field is changed, the critical current density of the specimens is not dependent upon the above angle. But, when the rolled plane is normal and the rolling direction is parallel to the applied magnetic field, the critical current density decreases to about 1/2 to 1/3 of the value for the specimen whose rolling direction is normal to the applied magnetic field.View full abstractDownload PDF (1172K) -
Masahiro Kitada, Toshio Doi1970 Volume 34 Issue 1 Pages 5-10
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe microstructures and textures of Nb-40Zr-10Ti superconducting sheets were investigated to find out the relation between the microstructure and the anisotropy of H-Jc (applied magnetic field-critical current density) characteristics and the dependency of the H-Jc characteristics upon the texture were discussed.
The source of the H-Jc characteristics is the anisotropic distribution of dislocations and precipitates which are introduced in a stage of heat treatment and rolling, Jcmin (rolled plane ⊥ applied magnetic field) to Jcmax (rolled plane\varparallelapplied magnetic field) ratio in a transverse magnetic field is in proportion to a⁄(a+d), where a and d are the thickness of the “imperfect layer” and of the “perfect layer” in the section of the specimen, respectively.
The dependency of the texture upon the H-Jc characteristics is not observed.View full abstractDownload PDF (2359K) -
Masahiro Kitada, Toshio Doi1970 Volume 34 Issue 1 Pages 11-16
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of oxygen on various properties of superconducting Nb-40Zr-10Ti alloy was investigated. The H-Jc (applied magnetic field-critical current density) characteristic in a transverse magnetic field at 4.2°K, the superconducting transition temperature Tc, the microstructure and the mechanical property of the specimens were examined.
The results are as follows:
(1) Jc of Nb-40Zr-10Ti alloys increases with the addition of oxygen. The main reasons for the increase of Jc of the specimens are considered to be the following three. [(a)] The pinning force which impedes the motion of the flux line increases with the existence of solute oxygen. [(b)] The interaction between the flux line and the β′+β″ lamella is strengthened by the refining of the β′+β″ structure (aged at 700°C). [(c)] The β→β′+β″ reaction is accelarated by the existence of oxygen. The increase in Jc for the specimens aged at 700°C are therefore due to more than two reasons mentioned above.
(2) Tc of the alloy decreases with the addition of oxygen.
(3) The tensile strength and the brittleness of the specimens increase with addition of oxygen.View full abstractDownload PDF (2077K) -
Tatsuzi Yamamoto, Keita Kawamura, Takaaki Hara1970 Volume 34 Issue 1 Pages 16-22
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetic properties of thin Sendust-alloy films are investigated. The films are obtained by vacuum evaporation onto heated glass substrates. Characteristic experimental results are as follows:
(1) Magnetic anisotropy which seemes to be due to oblique-incidence occurs in each samples. But through annealing in a vacuum, it decreases asymptotically with time.
(2) Magnetic properties are changed by diffusion of atoms and reduction of anisotropy during annealing. And each characteristic value approaches its final value after 1 hr.
(3) The relation between coercive force and film thickness corresponds qualitatively to Nèel’s Theory.
(4) The relation between magnetic properties and film constitution corresponds to that of bulk samples.
A tentative explanation of the results is given on the basis of the known structural properties of films.View full abstractDownload PDF (1904K) -
Masamichi Kowaka, Taishi Moroishi, Hiroo Nagano1970 Volume 34 Issue 1 Pages 23-32
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRapid laboratory test methods were studied to develop more economical and corrosion resistant steels for sulfur dewpoint corrosion in the low-temperature parts of boilers.
The correlations between three kinds of laboratory tests and the field tests in the low-temperature parts of boilers were investigated, and the effects of several alloying elements on the corrosion resistance of steels were discussed.
The results are summarized as follows:
(1) Immersion test in sulfuric acid: The immersion tests in sulfuric acids at various concentrations and temperatures which were determined from the liquid-vapor equilibrium diagram of sulfuric acid at the vapor pressure, PH2SO4+PH2O=0.1 atm, were carried out to investigate the effects of alloying elements. The correlation between the immersion test in sulfuric acid and the field test was insignificant.
(2) Corrosion test with an apparatus using the sulfuric acid condensation method: Sulfuric acids were condensed on the surfaces at 80°, 110° and 140°C in a flowing gaseous mixtures of SO3, H2O and N2. The effects of the surface temperatures on the corrosion rates of various steels and difference between the corrosion behaviors of the steels were investigated. This test was characterized by the presence of a very small amount of sulfuric acid on the exposed areas of the specimens, simulating the actual corrosion condition. The experimental results proved, however, not to be so well correlated with those of the field test. Although the main corrosion product in the laboratory test was monohydrated ferrous sulfate as in the field test, the existence of a large amount of unburned carbon in the field test was thought to be the cause for the differentiation of the corrosion behavior.
(3) Corrosion test in the mixture of sulfuric acid and active carbon: The corrosion tests in the mixtures of sulfuric acid and active carbon powder were done in view of the catalytic oxidizing action by unburned carbon, i.e., active carbon. The results of the tests in the mixtures of which sulfuric acid concentrations were determined as 80 or 85% from the common corrosion environment in actual boilers were very well correlated with the field tests. Therefore, this method was thought to be a useful laboratory test method for developing corrosion resistant materials and prediction of the life of not only the tubular-type but also Ljungstrom-type air preheaters, and economizers.View full abstractDownload PDF (2573K) -
Masamichi Kowaka, Hiroo Nagano1970 Volume 34 Issue 1 Pages 32-39
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo clarify the mechanism of sulfur dewpoint corrosion of steels, measurements of the corrosion potentials of steels in the mixtures of sulfuric acid-commercial active carbon powder and sulfuric acid-boiler deposit were carried out, and the effects of active carbon and unburned carbon in boilers on the corrosion were discussed from these results. Further, the anodic polarization curves of steels in sulfuric acid of high temperature and concentration were measured so as to investigate the relation between the anodic polarization characteristics and the resistance of steels for sulfur dewpoint corrosion. The experimental results may be summarized as follows.
(1) In the mixtures of 65∼85% sulfuric acid and active carbon at 110°C, the corrosion potentials of corrosion resistant steels containing chromium or boron shifted exceedingly in the noble direction, while those of non-corrosion resistant steels such as mild or copper steel hardly changed during the test period. It means that the former became the first stage passive state, and the latter still retained the active state. The commercial active carbon powder exerted the same influence as unburned carbon in the boiler deposit on the corrosion mechanism.
(2) The first stage passive current densities of steels in the anodic polarization curves in 80 or 85% sulfuric acid at 110°C decreased with increasing chromium content in steels. The low first stage passive current density correlated with the high resistivity for sulfur dewpoint corrosion.
(3) The mechanism of sulfur dewpoint corrosion seems to be composed of the corrosion process of three steps. The first step is the corrosion of steels in the sulfuric acid of relatively low temperature and concentration, the second step is in the sulfuric acid of high temperature and concentration, and the third step is in the unburned carbon sufficiently containing sulfuric acid of the same temperature and concentration as in the second step. The corrosion rates of steels may be determined chiefly by the corrosion of the second and third steps. Corrosion resistant steels containing chromium or boron bccome the first stage passivation in the third step process, and their corrosion rates are extremely retarded.View full abstractDownload PDF (1964K) -
Hakaru Masumoto, Yûetsu Murakami, Masakatsu Hinai1970 Volume 34 Issue 1 Pages 40-44
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMasumoto et al. previously discovered high permeability alloys near in composition to Ni3Mn which have an optimum degree of order, and named them “Nimalloy”. Much subsequent work has since been carried out so as to investigate the effects of various additive elements on the properties of nickel-manganese alloys as a result, the highest initial permeability of 76000 and the highest maximum permeability of 441000 have been obtained in the Ni-Mn-Fe-Cr system.
The data on niobium additions to nickel-manganese alloys show that the initial and maximum permeabilities of nickel-manganese alloys at first increase gradually and later rapidly reach their maxima, and then decrease gradually. The alloy consisting of 77.55%Ni, 19.52%Mn and 2.93%Nb exhibits the highest initial permeability of 32500 when cooled at a rate of 240°C/hr from 900°C and reheated at 440°C for 41 hr, and the highest maximum permeability of 151000 when cooled at a rate of 240°C/hr from 900°C and reheated at 420°C for 80 hr. In the latter case, the alloy shows a coercive force of 0.0149 Oe and a magnetic hysteresis loss of 22.00 erg/cm3/cycle for the maximum magnetic induction of 5000 G, and an electrical resistivity of 50.4 μΩ-cm at 20°C.View full abstractDownload PDF (1523K) -
Teruji Nojiri, Fusao Hayama, Shigeo Ôya1970 Volume 34 Issue 1 Pages 45-51
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relation between the casting structure and sliding wear properties and of lead and tin as the major components of lead-bronze was investigated. The test pieces were cut out from the chilled, columnar and equi-axial structures of lead-bronze ingots of different composition and were slid on a hardened steel ring in air without any lubricant.
The results obtained are as follows:
(1) The equi-axial crystal part in the casting structure shows the best anti-wear properties, followed in order by the columnar crystal and the chilled crystal is the worst generally. These trends are remarkable in the high lead and high tin alloy.
(2) The worn surfaces of the chilled structure are always metallic and the wear phenomenon is severe. The surfaces of columnar crystals are metallic or oxidized. The degree of oxidation depends on the compositions and sliding conditions, and is not satisfactory as compared with the equi-axial crystals. The surfaces of the equi-axial crystals are easily oxidized and the amount of wear is very small, while the wear of the steel ring is often severe.
(3) It is considered that the wear of lead-bronze is influenced by the distribution and shape of lead and the contents of Pb and Sn. The size of lead in the equi-axial crystal structure is relatively large and its distribution is relatively continuous each other. This form of lead is more preferable for wear resistance than the fine and isolated form of lead in the chilled structure.
(4) The materials with stable oxidizing wear seize the mating steel and show a high coefficient of friction, and these phenomena are relaxed by a suitable lead addition.View full abstractDownload PDF (2905K) -
Heitaro Yoshida, Kisaburo Koike, Renpei Yoda1970 Volume 34 Issue 1 Pages 52-58
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain forgeable chromium-base alloy having excellent creep rupture strength, various kinds of 60% chromium-base alloys, containing more than 10% molybdenum, boron, titanium, zirconium and carbon, and the alloys in which a part of iron was replaced with cobalt were melted in vacuum. The possibility of hot forging and the effect of these elements on the high-temperature properties were then investigated.
The results obtained are as follows.
(1) When ingots are heated, protection from the heating atmosphere is needed, and the preferable heating temperature range is 1200°∼1300°C than the range of 1100°∼1200°C.
The range in which hot working is possible is up to 20% molybdenum by dynapak forging, while it is up to 15% molybdenum by press forging. The conditions in which hot working is possible mainly depend on the alloy composition, with no relation to the purity of raw materials.
(2) Addition of a small amount of titanium is effective for improvement of ductility at high temperature. But, the addition of a large amount of titanium causes the alloy to precipitate the σ phase easily, thus deteriorating the ductility at high temperature of the alloy.
(3) Additions of carbon, boron, zirconium and titanium have a little effect on the improvement of creep rupture time. Selection of an optimum alloy composition is essential to increase the molybdenum content and also to utilize the precipitation of the σ phase in the range in which hot working is possible.
In this study, the composition in which hot working is possible and has a most excellent creep rupture strength is 58%Cr-12.5%Mo-5%Co-2%Ti-bal. Fe.View full abstractDownload PDF (3653K) -
Eiichi Takeuchi1970 Volume 34 Issue 1 Pages 59-64
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe author investigated the wear mechanism in the unlubricated sliding wear for Cu-Be alloy combined with the dissimilar metal (carbon steel; S55C) and also the phenomenon of the metal transfer in the adhesive or thermal wear range.
The following fact becomes clear that when BeA-50 (hardness at after aging; HRC 19-23) is used as a stator, the oxidation caused the main wear at a sliding velocity of 0.05∼0.20 m/sec, under a contact pressure of 5 kg/cm2, but in BeA-25 alloy (hardness at after aging; HRC 38-42), the adhesive phenomenon appears at a sliding velocity of 0.05 m/sec. When the velocity is between the above value and 0.70 m/sec, however, every alloy sufferes a great wear loss owing to the scratching or turning up operation by the adhesive wear marks or the wear debris existing between the sliding surfaces. Besides, the wear resistance in this range is better in BeA-25 alloy with higher hardness. When the velocity is about 4.00 m/sec, the thermal wear occurs and the conspicuous metal transfer as well as the high temperature oxidation was observed; the wear loss was comparatively small.
From the wear tendencies observed under the different wear mechanisms, the following fact becomes clear: in the oxidative wear range, the increasing rate of wear loss is small and the wear loss in the adhesive wear range increases almost linearly in proportion to the increasing sliding length, but in the thermal wear range, the high temperature oxidation and the increasing rate of the wear loss is small.
As the parts generated the metal transfer in the process of wear showed the wear between the metals of same kind, they transfer all the more easilly. Besides, the transfer-metal generated under the high velocity cracked owing to the thermal shock and the diffusion phenomenon between the matrix metals was observed.View full abstractDownload PDF (1973K) -
Yoshimichi Masuda, Ryuzo Watanabe, Masanori Hinata1970 Volume 34 Issue 1 Pages 65-70
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe sintering behaviors of three typical Fe-Cu, Ni-Ag, and Fe-Ag systems that are different in wetting characteristics have been studied. The isothermal shrinkage curves are divided into three stages on the log-log plot in every system. The first and the third stage of shrinkage can be represented by straight lines, whereas the slope of the second stage decreases gradually to that of the final stage. In the first stage relatively large voids were formed by the viscous flow of the liquid. The shrinkage in the second stage occurs by the penetration of liquid into the voids and the diffusion of gases through liquid, and in the final stage by the diffusion of gases from the voids isolated in the solid skelton.View full abstractDownload PDF (2753K) -
Yoshiyasu Sakamoto1970 Volume 34 Issue 1 Pages 71-77
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPrecipitates of nitrides are very important recrystallized structures in Al-killed low carbon steels. In the present paper, precipitation behaviours of nitrides at 500°∼750°C in hot-rolled sheets and cold-rolled sheets of Al-killed low carbon steels were measured by means of the internal friction technique. (Specimen size: 1∼1.5 mm t×10 mm w×150 mm l, flexural vibration). And preferred orientations of recrystallized materials were also investigated by the X-ray diffraction technique.
In order to measure the solute nitrogen, two methods of heat treatment were adopted.
(1) In order to separate the Snoek peaks of carbon and nitrogen, internal frictions were measured after annealing at 200°C for 3 hr.
(2) Snoek peaks could not be measured in the cold worked or polygonized materials because of the influence of lattice defects, so the solute nitrogen was measured after a short-time recrystallizing treatment (600°×15′), during which the precipitation might not occur.
The results are as follows:
(i) The rate of precipitation is increased with the amount of soluble Al.
(ii) Sheets in which the nitrides are precipitated at polygonization stages have stronger (111) textures than the materials which were recrystallized before the precipitation.View full abstractDownload PDF (2640K) -
Tsugio Tadaki, Ken’ichi Shimizu1970 Volume 34 Issue 1 Pages 77-83
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe martensitic transformation in the ordered Fe3Pt alloy was studied crystallographically by means of electron microscopy. The bcc martensite was found to have a superlattice which was expected to be formed by the Bain distortion from the Cu3Au-type superlattice of the γ phase. A number of transformation twins on the {112} type (not of the {211} and {121} types) plane were observed in the martensite. The habit plane of martensite plates and the orientation relationship between the martensite and austenite were consistent with those in the disordered Fe-Pt alloy of the same composition.
The domain structure in the ordered γ phase was observed by using the dark field technique, and it was clarified that the Ms temperature dropped rapidly according as the size of domain increased.View full abstractDownload PDF (2245K) -
Tadayuki Nakayama, Toshiaki Osaka1970 Volume 34 Issue 1 Pages 83-87
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTa samples were heated in an 18-8 stainless steel autoclave filled with deionized water. After heating, the oxide films were identified by means of transmission electron diffraction using an accelerating potential of 100 kV, and then component elements in the thin films were detected by using electron probe micro-analyzer.
The electron diffractogram of the film formed on Ta in deaerated high-temperature water by oxidation at 300°C for 1 hr or 24 hr indicated apparently the presence of only the rutile crystal structure. In addition, FeKα13 and TaLα15 characteristic X-ray spectra with the presence of Fe and Ta were detected in the film, indicating that the film was composed of (Fe, Ta)O2. On the other hand, the oxide film produced on the Ta surface in aerated high-temperature water by oxidation at 300°C for 1 hr gave a diffraction pattern corresponding to a hexagonal type structure. The unit cell dimensions for the above oxide were calculated from the reflections (220), (204) and (224); a0=5.87 Å, c0=4.62 Å, c0⁄a0=0.79. Further, after heating for 24 hr, the electron diffractogram of the film indicated the presence of the hexagonal crystal structure and the rutile crystal. CrKα13 and TaLα15 were detected in the film, and ca 0.67 mg/100 mL Cr6+ ions were detected from the water in an autoclave after oxidation. Therefore it was presumed that the Cr ions were dissolved from the autoclave and contributed to the formation of the hexagonal type oxide.View full abstractDownload PDF (1444K) -
Minoru Nobuki, Kyôji Tachikawa1970 Volume 34 Issue 1 Pages 88-94
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNb-Zr alloys containing 25, 50 and 70 at%Zr were fabricated into long fine wires. The most suitable lubrication for the drawing was coating of the wires with a layer of graphite or MoS2. The layer was formed by smearing colloidal solutions of these lubricants and subsequent drying up at 120°∼150°C in hot blasts. The friction coefficients between the wires and the WC drawing dies were measured by the separate die method. The friction coefficients during the continuous drawing were 0.07∼0.08 for graphite coating and 0.05 for the additional coating of MoS2. These values were a few tens of percent larger than those measured by the reciprocal friction testing machine. The die angle which minimized the drawing force was between 18° and 20°. The drawing forces which were calculated by formula (3) of this paper were in good agreement with the observed values. The influences of the intermediate annealing temperatures and the reduction of drawing upon mechanical and superconducting properties of the wires were also investigated. The wire annealed between 700°C and 850°C and then drawn about 96% showed the highest superconducting current capacity.View full abstractDownload PDF (2090K) -
Yasuo Kimura, Kimiyuki Kamino1970 Volume 34 Issue 1 Pages 94-101
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDirectional magnetic properties are observed in SmCo5-SmCu5 system alloy, which was subjected to freezing in a direction normal to the cold surface of the copper hearth. The maximum energy product, (BH)max, of 65 wt%SmCo5-35 wt%SmCu5 alloy is 5.78 MGOe in the as-cast state when the measurement is carried out in the direction perpendicular to the chill plane. By annealing at 300°C for 1 hr, (BH)max value increases to 7.73 MGOe with Br=6450 G and BHc=3400 Oe. The magnetic properties in the direction perpendicular to the chill plane are superior to the other directions and the chill plane shows weak texture, (0001). These alloys have the easy direction of magnetization, which is the c-axis of the hexagonal crystal as SmCo5.
The lattice constants of both a- and c-axes of the hexagonal crystal enlarge linearly with increasing copper content. The value of lattice constant ratio c⁄a is approximately 0.802 in all the alloys. The results of X-ray micro analysis suggest that the alloys of this system alloy have congruent points and miscribility gaps in solid solution on a quasi-binary diagram.View full abstractDownload PDF (2174K) -
Goro Ito, Tadao Ishihara, Yoshihiko Shimizu1970 Volume 34 Issue 1 Pages 101-107
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of such impurities as carbon, silicon, manganese and phosphor on the resistance to stress corrosion cracking of austenitic stainless steels were studied in pressurized, high temperature water containing chloride.
The tests were carried out at 300°C for 300 hr in an autoclave that contained the testing solution with a concentration of 600 ppm chloride ion prepared from sodium chloride and pure water.
The results are summarized as follows:
(1) In alloys containing from 0.05 to 0.2 per cent of carbon, the alloys with less than 0.1 per cent carbon were immune to cracking, but those with more than 0.1 per cent carbon became slighly susceptible to cracking. Furthermore, when the carbon content increased to 0.2 per cent, the alloys became remarkably susceptible to intergranular cracking.
(2) The alloys with less than 2 per cent silicon were slighly susceptible. When the silicon content increased to 5.4 per cent, the sucesptibility to cracking increased remarkably.
From the results of hydrogen charging tests, it seems that cracks in the alloys are caused by hydrogen embrittlement in the presence of martensite in their structures.
(3) The addition of less than 0.5 per cent manganese to the alloys had no appreciable effect on the susceptibility to cracking, but the alloys containing more than 1.5 per cent manganese became remarkably susceptible.
(4) The susceptibility to cracking for the alloys containing 0.03 to 1 per cent phosphor increased with increasing phosphor content.
(5) It is evident from the experimental results that in the alloys containing the same amounts of impurities as in commercial steels both phosphor and carbon contained in the alloys were harmful elements to cracking.
In general, the alloys containing the above-mentioned impurities were also susceptible to cracking in a boiling MgCl2 solution, but it was found that harmful elements to cracking in this environment were not limited to phosphor and carbon.View full abstractDownload PDF (2012K) -
Ryo Horiuchi, Junichi Kaneko, A. B. Elsebai, M. M. Sultan1970 Volume 34 Issue 1 Pages 108-115
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInvestigation was made in some detail so as to evaluate the characteristics of the hot torsion test, and an adequate method of evaluation of hot workability of aluminum alloys under hot working conditions was discussed. The most important point is that heat generated by the work of deformation causes a temperature rise, nonuniform temperature distributions and hence nonuniform distributions in shear strain in the specimen. Taking the effects of temperature rise into consideration, the solid cylindrical specimen test is preferred to the tubular specimen and differential test, and shorter gage length is desirable. Temperature change in the specimen was measured during torsional deformation, and a reasonable agreement was obtained between the measured values and the calculated ones which were obtained by solving the differential equations of unsteady heat transfer with proper boundary conditions.View full abstractDownload PDF (2493K) -
Riei Ichikawa, Teruo Ohashi1970 Volume 34 Issue 1 Pages 115-120
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structural change and some incidental properties of Al-Cr (up to 3 wt%) alloys by rapid solidification at varying cooling rates 102 to 103°C/sec were investigated. The results obtained are as follows: (1) It is shown that the supersaturated solid solutions can be formed by rapid solidification and the minimum cooling rate to dissolve solute Cr supersaturatedly in pure Al is more than about 600°C/sec for 2 wt%Cr and about 1000°C/sec for 3 wt%Cr, respectively. (2) The microstructure of these solid solutions are composed of the dendritic cell structure of the primarily crystallized α phase and appearance of CrAl7, which has to crystallize primarily in an equilibrium condition, is obstructed. (3) The decomposition temperature of the supersaturated solid solutions of Al-2 wt%Cr alloys is 250°∼300°C and is lower by 100°C than that of Al-Mn system. (4) No precipitation hardening cannot be recognized by decomposition of these supersaturated solid solutions.View full abstractDownload PDF (1223K) -
Akio Hara, Tadashi Ikeda1970 Volume 34 Issue 1 Pages 120-125
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDeformation and fracture mechanism by compression of WC-Co cemented carbide was studied by measuring and observing stress-strain curves, micro-structure and physical properties. It was found that micro-fracture in the alloy structure occurred in far advance of specimen’s fracture. Stress-strain curves were deviated from empirical σ=Aεn law from ε=0.2%, and a maximum stress was attained at about ε=1% or more, further, the stress was decreased with an increase of strain until fracture. With micro-structure changes, density, hardness, coercive force and poisson’s ratio were changed. Phase transformation of the cobalt phase was detected. Specimen’s fracture was caused by boundary fracture of the WC phase irrespective of grain size and cobalt content in the alloy.View full abstractDownload PDF (2027K)
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