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Volume 26, Issue 11
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Mikio Yamamoto1962 Volume 26 Issue 11 Pages 689-694
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFirstly, the thermal factor or the temperature distribution, in particular, the temperature gradients in the solid and in the liquid at the solid-liquid interface, Gso and Glo, the crystallographic factor or the direction of preferential crystal growth, and the impurity factor or the constitutional supercooling, and their dependence on the crystallization velocity, Ri, and the furnace temperature gradient, Gf, are discussed for the case of solidification. It is shown that the conditions necessary for growing successfully single crystals from the melt are the high purity of the material and the high value of the ratio Gf⁄Ri as already known empirically. Secondly, the yield percentage, S, of growing single crystals from the melt as dependent on Ri and Gf is considered. It is found that single crystals grow practically only when Glo is positive and that S is higher as Glo is larger. If, as the first approximation, S is taken to be proportional to Glo, the relation between S and Glo is given by S = S_o [1 - D {1 - (S/A)^1/2(σ_l/k_l)^1/2}^-1(R_i/G_f)], where D = (A/S)^1/2 ρ_sL/{(k_l σ_l))^1/2 + (k_s σ_s)^1/2}. Here So is the value of S for Ri→0, A and S the cross-sectional area and circumference of the specimen (their variation accompanying solidification are neglected here for simplicity), respectively, kl and ks the thermal conductivities of the liquid and of the solid, respectively, σl and σs the thermal emissivities of the liquid and of the solid, respectively, ρs the density of the solid, and L the latent heat of solidification. This expression indicates that S is higher as Gf⁄Ri is larger, as is known empirically, and it agrees, in the relation between S and Ri, with the experimental results obtained preirously by the author and Watanabé in growing single crystals of zinc, bismuth, and white tin by the Bridgman method. Finally, it is shown that, if the orientation distribution of single crystals grown from the melt is determined mainly by the counterbalance of the crystallographic and thermal factors of the solidification process, the probability of single crystal growth is the same for all orientations for small Ri⁄Gf and, as Ri⁄Gf becomes larger, it becomes larger for crystals with orientations along the preferred directions of growth, which accords with the observed facts.View full abstractDownload PDF (880K) -
Hirozô Kimura, Yasuo Sasaki1962 Volume 26 Issue 11 Pages 695-699
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing the vacuum process, carbide reduction of niobium pentoxide due to the following reaction was investigated experimentally : Nb2O5+5NbC=7Nb+5CO. The mixing ratio of Nb2O5/NbC was varied from 33/67 to 45/55. By means of fluctuation measurements of pressure and temperature, it was clarified that the reaction began to proceed rapidly above 1700°C. Crude niobium metal, containing 96 to 97%Nb, was obtained easily by this process. The purification of crude niobium metal obtained above was examined in a series of vacuum refining experiments. Impurities, such as carbon, oxygen and nitrogen in niobium metal decreased at the refining temperature above 2150°C at the pressure of 10−5 mmHg. The removal of carbon during refining process was dependent on both temperature and oxygen content. Rapid removal of oxygen was observed in the presence of carbon. Cold-rolling was attempted on each specimen of refined metals, and fabricable specimens containing above 99.7%Nb showed the Vickers hardness lower than 200.View full abstractDownload PDF (908K) -
Hirozô Kimura, Yasuo Sasaki1962 Volume 26 Issue 11 Pages 699-703
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCrude niobium metal containing about 99%Nb was obtained from a mixture of niobium pentoxide and niobium carbide by arc reduction by the following reaction: Nb2O5+5NbC→7Nb+5CO. Mixtures of niobium pentoxide powder and niobium carbide powder were pressed into briquettes. To proceed with the above reaction at high temperature, they were arc-melted by using a laboratory argon-arc furnace with tungsten electrodes and a water-cooled copper crucible. The effects of melting time, argon pressure and number of times of remelting on the reaction were investigated. The purity of reductants as crude niobium metal, the composition of furnace gas and the weight losses during arc melting were examined. It was observed that a large amount of CO gas was generated from the molten specimen during arc-melting. Increase of niobium content in reductants was remarkable on account of both the reaction and the vapourization of niobium monoxide especially in low pressure melting.View full abstractDownload PDF (480K) -
Yoshikazu Yamamichi1962 Volume 26 Issue 11 Pages 703-707
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe Höganäs’ sponge iron process has been studied with the intention of producting iron powder for sintered products and welding bars. In order to design a suitable tunnel kiln for plant layout, the kinetic equation based on knowledge about its reduction mechanism had to be determined. At first, in this report, the unsteady thermal conduction of a sagger was solved by a graphical solution based on Schmidts’ method.View full abstractDownload PDF (610K) -
Shozo Yoshioka, Yutaka Nakayama1962 Volume 26 Issue 11 Pages 707-712
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe distribution and behaviour of dislocations, and also the fine structure of mechanical twin in magnesium deformed at room temperature were studied by means of the transmission electron microscopy. The most striking feature of dislocations in deformed magnesium was that the dislocations piled up toward the grain boundary. Besides this, the entangled dislocations were found along the twin boundaries. From these phenomena, some inferences are made as to the probable trend of the work-hardening of polycrystalline magnesium deformed at room temperature. Evidence was found for the occasional separation of perfect dislocations into partial ones separated by a stacking fault. However, the loops of prismatic dislocations containing a stacking fault probably originated in the precipitation of vacancies could not be found even in magnesium severely deformed at room temperature and quenched magnesium.View full abstractDownload PDF (1887K) -
Kikuji Satô1962 Volume 26 Issue 11 Pages 713-718
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn anomaly which occurs in annealing in the temperature range between 250°C and 450°C was investigated with commercial Cu-Ni-Zn alloys. The electric resistance and its temperature coefficient of cold-drawn wires and of wires which were water-quenched and furnace-cooled from 500°C were measured at 21°C and −196°C. (1) The electric resistance of cold-drawn wires increased gradually in the temperature range between 100°C and 300°C during isothermal annealing. (2) Its reaction was of second order and its activation energies were 2.5 kcal/mol and 25 kcal/mol at 100°∼200°C and 200°∼300°C, respectively. (3) During isochronal annealing process, both cold-drawn wires and water-quenched wires showed maxima of electric resistance and of its temperature coefficient between 250°C and 450°C. (4) but in these wires, an effect of over-aging on electric resistance and monotonous increase of its temperature coefficient were observed in a long-time or high-temperature isothermal annealing. (5) Etching bands were observed under an electron microscope only on a surface of the specimen which showed high electric resistance. From these results it seemed difficult to explain the anomaly in nickel silver alloys only with the mechanism of ordering. Therefore the author suggests that segregation of Zn atoms to stacking faults may explain the above and some of the recent experimental results.View full abstractDownload PDF (1126K) -
Kichizo Niwa, Satoshi Kado, Tadanori Itoh, Ken Tsuchiya1962 Volume 26 Issue 11 Pages 718-722
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe diffusion coefficients of silver in molten lead and bismuth at infinite by high dilution were studied within the temperature ranges of 451°∼639°C and 383°∼599°C, respectively, using the capillary method and with Ag110 as the radioactive tracer. The obtained results can be represented by & D_Ag in Pb = (3.13±0.25)×10^-4 exp(-3430±60/RT) cm^2/sec
& D_Ag in Bi = (8.19±0.79)×10^-4 exp(-4100±60/RT) cm^2/sec The relationship between diffusion and viscosity proposed by Einstein, Sutherland, Eyring, Li and Chang and Longuet-Higgins and Pople were tested by the obtained experimental results. It was found that the values calculated by the Sutherland, Longuet-Higgins and Pople’s equations showed good agreement with the experimental data, and hence these equations are adequate for these liquid metallic solutions.View full abstractDownload PDF (554K) -
Kichizo Niwa, Satoshi Kado, Tadanori Itoh, Ken Tsuchiya1962 Volume 26 Issue 11 Pages 722-726
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBy the use of the capillary method and Ag110 as the radioactive tracer, studies have been made of the diffusion of silver in molten tin and cadmium within the temperature ranges of 387°∼590°C and 364°∼541°C respectively. The results obtained can be represented by & D_Ag in Sn = (7.34±0.66)×10^-4 exp(-4180±60/RT) cm^2/sec
& D_Ag in Cd = (5.68±0.90)×10^-4 exp(-4380±90/RT) cm^2/secIn the same manner as stated in the previous report, the relationship between diffusion and viscosity was tested by the obtained results and it was found that the Sutherland and Longuet-Higgins-Pople equations are quite useful in evaluating the diffusion coefficient of dilute solutions.View full abstractDownload PDF (638K) -
Kichizo Niwa, Satoshi Kado, Tomeji Ohno1962 Volume 26 Issue 11 Pages 726-730
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe diffusion coefficients of silver in molten copper at infinitly high dilution have been studied within the temperature range of 1143°∼1290°C by the use of capillary method and Ag110 as radioactive tracer. The obtained results can be represented by D_Ag in Cu = (1.93±0.43)×10^-3 exp(-11210±285/RT) cm^2/secThe dependence of diffusion coefficients of silver in Cu-Ag system upon the concentration has been studied at the concentration of silver, NAg=0.146 and in the temperature range of 1150°∼1311°C. The obtained results can be represented by D_Ag in Cu-Ag (N_Ag = 0.146) = (6.81±1.96)×10^-4 exp(-9030±330/RT) cm^2/sec.View full abstractDownload PDF (552K) -
Kazuo Tsuya, Noriyoshi Aritomi1962 Volume 26 Issue 11 Pages 730-734
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe ductility of molybdenum, processed to sheets from electron-beam melted ingots, was compared with that of commercial sintered molybdenum sheets. Molybdenum powder with 0.06 pct carbon was electron-beam melted in a water-cooled copper boat, which was moved horizontally. The ingots (8×15×200 mm) were hammered and rolled to the sheets 1 mm and 0.3 mm in thickness. The specimens, cut from electron-beam melted molybdenum sheets and sintered ones, were fully recrystallized at 1300°C. The bend angles and the tensile properties of these specimens, were determined at temperatures ranging from −100°C to 25°C and from −90°C to 150°C, respectively. The results obtained are summarized as follows: (1) A fully recrystallized structure was observed at 1100°C in sintered molybdenum, while electron-beam melted molybdenum recrystallized completely at 1000°C with coarser recrystallized grains. (2) In tensile tests at temperatures ranging from −50°C to 25°C, the amount of elongation after necking had occurred was larger in electron-beam melted specimens than in sintered specimens. (3) The ductility-transition temperature below which completely brittle fracture occurred was about 30°C lower in electron-beam melted molybdenum than in sintered molybdenum.View full abstractDownload PDF (623K) -
Hiroshi Kimura, Ryukiti R. Hasiguti1962 Volume 26 Issue 11 Pages 735-737
Published: 1962
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe respective thermal electro-motive force of cold drawn and fully annealed copper wires was measured to investigate the change in thermo-electric power due to cold working, and its recovery was investigated together with the release of internal strain energy while heating the wire. Recovery of the thermo-electric power occurred in two stages corresponding to the two steps of release of strain energy. In the first stage 12% of the total change in thermo-electric power was recovered and 30% of the internal strain energy was released. In the second stage, i.e., recrystallization, the thermo-electric power recovered to the annealed state and the release of strain energy ceased. The first stage is considered to be due to annealing out of vacancies produced by deformation, and the change in thermo-electric power due to excess vacancies is estimated to be 0.6 μV/°C per 1 at% vacancies. The second stage is considered to be due to annihilation of dislocations and the change in thermo-electric power due to dislocations is estimated to be 5×10−19 NV/°C, where N is the dislocation density.View full abstractDownload PDF (555K)
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