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Volume 34, Issue 7
Displaying 1-18 of 18 articles from this issue
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Hiroshi Ikawa, Shigeo Shin, Masakazu Miyagi, Masaki Morikawa1970 Volume 34 Issue 7 Pages 673-679
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe transition phase, ω, which is formed during the transformation β⁄β+α makes the alloys very hard and brittle. This ω phase was investigated by transmission electron microscopy in the Ti-Mo (β isomorphous type) and the Ti-Mn (β eutectoid type) system. The ω phase in Ti-Mo alloys is ellipsoidal with a major axis parallel to ⟨111⟩β, its maximum size being about 2000 Å. On the other hand, the shape of the ω phase in Ti-Mn alloys is cubic with a habit plane {100}β, its maximum size being about 300∼350 Å. The ω phase in the quenched material (ω′) of Ti-Mo alloys is formed more easily with the decrease of solute atom contents and extends in the form of a very fine needle parallel to ⟨111⟩β.View full abstractDownload PDF (2192K) -
Iwao Tsukahara1970 Volume 34 Issue 7 Pages 679-684
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe concentration and activity of oxygen in molten copper and copper-tin alloy have been measured by the galvanic cells,
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over the temperature range of 1100°∼1250°C for the oxygen concentration range of 2∼1000 ppm and for the tin mole fraction of 0∼5.5×10−2.
The activity of tin in molten copper-tin alloy has also been measured.
These measurements have shown that:
(1) The activity of oxygen in copper follows Henry’s law in the measured concentration range of oxygen and its activity coefficient is expressed by the equation,
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(2) The activity of oxygen in the copper alloy with a tin mole fraction of 7.0×10−4 follows Henry’s law in the measured concentration range of oxygen.
(3) The activities of oxygen in copper alloys with tin mole factions of 2.6×10−3, 5.3×10−3, 2.7×10−2 and 5.5×10−2 follow Henry’s law in the higher concentration range of oxygen but do not in the lower concentration ranges. And their activity coefficients decrease with decreasing oxygen concentration.
(4) The activity coefficient of oxygen in copper-tin alloys decreases with increasing tin concentration.
(5) The activity of tin in copper-tin alloys follows Henry’s law in the measured concentration range of tin and exhibits a large negative deviation from Raoult’s law.
Its activity coefficient can be written as logγSn=−2.805×103⁄T+0.6557
The solubility of oxygen in molten copper-tin alloys has also been discussed.View full abstractDownload PDF (1466K) -
Norio Ichinose1970 Volume 34 Issue 7 Pages 685-690
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSRecommendable spectrophotometric methods have been developed for the determination of microamounts of chromium and molybdenum in high-purity thorium compounds.
In the case of chromium, a sample is dissolved in nitric acid containing a few drops of hydrofluoric acid by heating, and the solution is treated with potassium permanganate and urea·sodium nitrite as the oxidizing agent. The solution is mixed with diphenylcarbazide, and the absorbance of its color developed in the solution is measured at 540 mμ.
In that of molybdenum, a sample is dissolved in hydrochloric acid containing a few drops of hydrofluoric acid by heating, and the solution is treated with potassium bromate-bromide as the oxidizing agent. Molybdenum (VI) in the hydrochloric acid solution (approximately 5.5 N) is extracted into n-butyl acetate. The n-butyl acetate extract is shaken with a potassium thiocyanate solution containing stannous chloride and hydrochloric acid, and the absorbance of its color developed in the organic phase is measured at 472 mμ.
These methods are applied to the determination of chromium above 0.1 ppm (Cr/ThO2) and of molybdenum above 1 ppm (Mo/ThO2) respectively.View full abstractDownload PDF (2049K) -
Tamotsu Sato, Goro Ohira1970 Volume 34 Issue 7 Pages 690-696
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe interfacial transition from plane to cellular structure and the segregation pattern of Al-Cu alloys was investigated by means of a quenching method during unidirectional solidification.
The following results were obtained:
(1) The preferred grain boundary segregation occurred prior to the breakdown of the planar interface.
(2) Small holes appeared at random on the solid-liquid interface at the beginning of the transition.
(3) The holes were aligned or distributed regularly to form an elongated cell.
(4) The solidification proceeded entrapping the liquid phase at the bottom of the holes and resulted in the “rosary-like” segregation.
(5) The “rosary-like” segregation was also observed in hexagonal cell nodes.View full abstractDownload PDF (3355K) -
Tamotsu Sato, Goro Ohira1970 Volume 34 Issue 7 Pages 697-700
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the unidirectional solidification of Al-Cu alloy, the preferred grain boundary segregation, the holes distributed at random on the solid-liquid interface, the “rosary-like segregation”, etc. were observed to occur with the cellular breakdown on solidification. These phenomena can hardly be explained by the constitutional supercooling or by the M-S theory.
The authors have already discussed the stability of the small pits on the solid-liquid interface, and from this point of view these phenomena are discussed in the current paper.View full abstractDownload PDF (1041K) -
Mutsuo Ohta, Fumio Hashimoto1970 Volume 34 Issue 7 Pages 700-705
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAging behaviour of Al-Ag binary alloys containing less than 0.11 at%Ag and Al-Ag-Zn ternary alloys containing a small amount of zinc were studied by the measurement of electrical resistivity.
The results may be summarized as follows:
(1) After isothermal aging below a certain temperature, the electrical resistivity of each Al-Ag binary and Al-Ag-Zn ternary alloys increases initially, reaches a maximum value and then decreases corresponding to the formation and growth of G.P. zones. But when aged isothermally above a certain temperature, the electrical resistivity shows a slight initial increase and then decreases very slowly, with no distinct maximum in the isothermal aging curves. In this case, G.P. zones seem not to be formed and the small increase of electrical resistivity is related to some behaviour of the supersaturated solute atoms. Therefore, these critical temperatures seems to be the highest temperature at which G.P. zones can be formed in Al-Ag binary and Al-Ag-Zn ternary alloys.
(2) The highest temperature at which G.P. zones can be formed in Al-Ag-Zn alloys containing a small amount of zinc is higher than that in the Al-Ag binary alloy containing the same amount silver. Namely, G.P. zones becomes stable at the initial stage when a small amount of zinc is added. This effect become remarkable when the concentration of zinc increases.View full abstractDownload PDF (2164K) -
Kenzaburo Kumada, Hiroaki Tatsumoto1970 Volume 34 Issue 7 Pages 706-711
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHigh purity 25Cr-20Ni steels were melted in vacuum and air respectively, and the phase change due to annealing at 750°, 800°, and 850°C for 2∼1500 hr after casting or forging was studied by means of micro-Vicker’s hardness testing, magnetic analysis, X-ray diffraction and microstructure examination.
The results obtained are as follows:
(1) The δ-ferrite which remains in the as-cast and as-forged specimens is sigmanized in less than 100 hrs annealing at 750°∼850°C.
(2) In the high purity 25Cr-20Ni steels, annealed at 750°∼850°C for a long time, the higher the temperature, the more rapid the ferrite precipitation, and the ferrite precipitation is more rapid in the forged materials than in the cast ones.
(3) The precipitated ferrite is sigmanized gradually with the annealing time and most rapidly in the temperature range between 800° and 850°C.
(4) The ferrite precipitated in annealing disappeares more slowly than that of δ-ferrite which remains in the as-cast and as-forged specimens.View full abstractDownload PDF (2533K) -
Minoru Tanaka, Tomoo Suzuki1970 Volume 34 Issue 7 Pages 711-716
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt has previously been reported that the age-hardening process of Fe-Ni-Co martensitic alloys takes place in two stages where the initial hardening occurs due to ordering and the second occurs due to strain hardening of matrix. In this paper, the second stage hardening of these alloys during isothermal ageing was investigated metallographically comparing with the behaviours of the age-hardenable Fe-Ni-Mn alloys which were already reported.
The results obtained in this paper are summarized as follows:
(1) The precipitation of the austenite from the martensitic matrix occurs more easily in the hardening stage of the Fe-Ni-Co alloys than that of the Fe-Ni-Mn alloys.
(2) The second stage hardening of Fe-Ni-Co alloys is accompanied with the increment of the lattice parameter of the martensitic matrix and of the amount of the precipitated austenite.
(3) From some considerations based on the measurements of the lattice parameters of the austenite, it seems that the concentration of solute atoms in the austenite is lowered as the ageing process advances, and also that the ferrite conjugated with the austenite separates changing its concentration of solute atoms in the matrix. The main reason for the second stage hardening seems to be due to strain hardening occurred by the precipitation of the ferrite above mentioned.
(4) The results of the measurements of the order-disorder transformation points of Fe-Ni-Co alloys suggest that (i) Ni atoms are substituted for Co atoms when Ni atoms are alloyed to the Fe-Co ordered structure, and (ii) the ordering energy parameter of the Fe-Ni bcc phase is greater than that of the Ni-Co bcc phase.
Comparing with the energy parameters of bcc phases of binary alloy systems, such as Fe-Ni, Fe-Co, Ni-Co, Fe-Mn and Ni-Mn, it is concluded that the separation of the martensitic matrix into the two bcc phases due to the miscibility gap island is possible in the Fe-Ni-Mn system but impossible in the Fe-Ni-Co system.View full abstractDownload PDF (1849K) -
Masahiko Ogirima, Toshinari Hirayama, Muneyasu Nakajima1970 Volume 34 Issue 7 Pages 717-723
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMany metallic materials are put into practical use after strengthening or deforming into intended shapes by cold rolling, cold pressing or cold drawing. However, the fatigue strength does not always increase by cold deformation because of the increase of dislocation density and vacancy density or initiation of microcracks. Therefore, in order to clarify the relation between prestrain and fatigue strength, OFHC copper and Cu-36%Zn alloy (brass) were prestrained to various degrees and then fatigued to failure by the pushpull fatigue-test machine. The microstructures of the prestrained copper and brass were observed by optical and transmission electron microscopy, and the effects of prestrain on fatigue process were investigated.
As a result of the investigation, the fatigue limit of OFHC copper was found to decrease by prestraining of several per cents. This decrease was assumed to be due to the increase of free dislocations. However, by increasing the applied prestrain from few per cents up to 90 per cents, the fatigue limit of OFHC copper increased monotonously because of the formation of cell structures. On the other hand, the decrease of fatigue strength of the brass prestrained by a few per cent was very small, and the fatigue limit dropped down abruptly at the prestrain of about 20 per cents. The cause for this sudden decrease of fatigue strength seemed to be due to the formation of microcracks. The difference of the effect of microcracks on fatigue strength between OFHC copper and brass can be explained by the difference in notch sensitivity.View full abstractDownload PDF (2915K) -
Ishi Miura, Hitoshi Hamanaka, Tamio Isago1970 Volume 34 Issue 7 Pages 723-728
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEutectic and hypereutectic Al-Si alloys were rapidly solidified at solidification rates of the order of 103°C/sec and more, and their microstructures and mechanical properties were investigated. By the rapid solidification, extremely fine eutectic structures with an average silicon size of 0.1μ were produced, and the solid solubility of Si in Al was much increased. For hypereutectics, a uniformly refined eutectic structure without primary silicon was produced up to 17 wt%Si by the rapid solidification. Mechanical properties of the Al-Si alloys were considerably improved, especially in hardness by the “quench-modification”, the maximum values of which were obtained by the precipitation of silicon particles from the supersaturated solution when aged at 130°∼150°C for 2 hrs.View full abstractDownload PDF (2246K) -
Masao Fujii, Makoto Kumada1970 Volume 34 Issue 7 Pages 729-735
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe role of grain boundaries in pitting corrosion of 18-8 stainless steels was studied by means of the potentistatic technique, transmission electron microscopic observation and micro-vickers indentation measurements.
The following results were obtained:
(1) Observation results of transmission electron microscopy that pits initiate from the grain boundaries at which chromium carbides are precipitated show that local cells are produced as a result of the accumulation of impurities at grain boundaries, and also that the parts preferentially attacked due to the actions of cells grow into pits.
(2) The fact that pits form on the region of micro-vickers indentations shows that local cells are produced as a result of the presence of regions with weak or broken surface films and the high chemical potential, and also that the parts preferentially attacked due to the actions of cells grow into pits. It seems that such parts correspond to grain boundaries.View full abstractDownload PDF (3364K) -
Isao Ito, Shiro Haruyama, Kyuya Nagasaki1970 Volume 34 Issue 7 Pages 736-738
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the previous paper, it was reported that the dezincification of α-brass was remarkably affected by small amounts of metallic additives, and the effectiveness was discussed by considering the three types of concentration-profiles of the additives. In the case of the group of Si, Ge and Sn, an abnormal dezincification was suggested to be due to the ternary diffusion phenomena.
In this paper, the experiment on the ternary diffusion was carried out at 800°C in hydrogen atmosphere by the diffusion couple method, using 8 couples of alloys of Cu-Zn-X systems (X: Ge, Sn, Ag, Fe, Co, Ni, Ga and Mn). The ternary diffusion paths were determined by measuring the concentration using EPMA.
The results are summarized as follows:
(1) The concentration profiles of Si, Ge and Sn were concluded to be due to the ternary diffusion caused by dezincification.
(2) The profiles of Ag, Fe, Co and Ni were explained by considering the ternary diffusion.
(3) The profiles of Al, Ga, Mn and Cr were interpreted as due to the oxidation of those elements.View full abstractDownload PDF (1151K) -
Tsugio Ogura, Seiichi Karashima1970 Volume 34 Issue 7 Pages 739-745
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAluminium polycrystalline specimens of 99.99% purity were fatigued at room temperature by alternating tension and compression. Substructures near the tips of fatigue cracks were observed at various stages of crack propagation using an X-ray microbeam technique. Effects of the crack length and the alternating stress on the characteristics of substructures and the size of plastic zone were examined.
The main results obtained are as follows.
(1) Regardless of the fatigue stress and the crack length, a plastic zone, in which a well-defined substructure is observed, exists around a fatigue crack. The results are in good agreement with the results reported on some fcc metals and alloys fatigued by alternate bending.
(2) The following two factors may be effective in the formation of the well-defined substructure near the tip of a fatigue crack; the stress concentration at the tip of a fatigue crack and a large quantity of vacancies formed during stress cycling.
(3) The characteristics of the plastic zones revealed by the present study by means of structure observations are very similar to those of the plastic zones deduced from the data based on a macroscopic point of view. It seems possible, therefore, that both plastic zones are explained from the same standpoint.View full abstractDownload PDF (2730K) -
Tsugio Ogura, Seiichi Karashima1970 Volume 34 Issue 7 Pages 746-752
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThin-foil specimens of pure aluminium (99.99%) were fatigued at room temperature by an alternative bending apparatus. Structures around fatigue cracks formed in the foils were examined in an electron microscope operated at 500 kV.
As already revealed by transmission electron microscopy at 100 kV, well-defined substructure and strain-concentrated region were observed around a fatigue crack. It was confirmed that voids of 0.1∼1μ in size were formed in the vicinity of fatigue cracks. Voids were also observed in persistent slip bands and in sub-boundaries. Based on the experimental results, the mechanism of fatigue crack propagation due to the coalescences of the voids at the crack tip is suggested. Discussion on the process of void formation and the role of the substructure in fatigue crack propagation is described.View full abstractDownload PDF (3040K) -
Hiroyasu Mitani, Hiroshi Nagai1970 Volume 34 Issue 7 Pages 752-757
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAlthough several reports have been published in regard to an Al extracting method called the “gross process” utilizing the subhalide reaction between Al and AlCl3, very little has been known about the purity of Al produced by this reaction. On selecting the composition of the raw material, quality of the reaction vessel and purpose of the produced Al, it is very important to make clear the contamination route and contents of impurities.
In the present work, in order to clarify the contamination route and degree, Fe, Cu and Si in Al produced from Al-Fe, Al-Cu and Al-Si binary alloys have been determined by spectroscopic analysis.
As a result, the purification factors for Fe and Cu are about 2×104 and 1×104 respectively, but concentration of Si in the obtained Al is 0.25% constantly regardless of the presence of Si in the raw material.
The contamination route of the impurities is discussed from the experimental results and thermodynamic calculations. It has been made clear that the contamination by Fe, Cu and Si arises from the reaction between the oxides of the impurities and AlCl and AlCl3.View full abstractDownload PDF (1482K) -
Sakae Takeuchi, Hiroshi Katsuta1970 Volume 34 Issue 7 Pages 758-763
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe defect structure in the nonstoichiometric TiS2 phase ranging 2 to 1.82 in atom ratio S/Ti has been studied in relation to the distribution of excess Ti atoms over the stoichiometric composition TiS2.00.
From the measurement of the density, lattice constant and X-ray intensity ratio as a function of S/Ti, it is found that there are 2.7% vacancies at the (0 0, 0) site of the Ti-sublattice and the same amount of Ti atoms at the interstitial position (0 0, 1/2) for the stoichiometric composition, and the occupation of these two sorts of sites by the excess Ti depends upon the Ti concentration. The (0 0, 0) sites in the range S⁄Ti>1.9 and the (0 0, 1/2) sites in the range S⁄Ti<1.9 are mostly occupied by the excess Ti.
The problem of the lattice bonding is discussed in relation to the above defect structure.View full abstractDownload PDF (1678K) -
Sakae Takeuchi, Hiroshi Katsuta1970 Volume 34 Issue 7 Pages 764-771
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMeasurements of electric resistivity, Hall coefficient and magnetic susceptibility was carried out for various compositions in the nonstoichiometric TiS2 phase over the temperature range of 4.2°K to 300°K.
From the behaviours on the temperature dependence of electric conductivity measured for single crystals with Ti-concentrations from TiS2.00 to TiS1.94, it is suggested that (i) the metallic conductivity in the stoichiometric composition TiS2.00 comes from a slight over-lapping between the bottom of conduction band and the top of valence band, (ii) the Fermi level of TiS2.00 is in the vicinity of a minimum position of the density of states curve N(E) resulting from the overlap of bands, and (iii) the Fermi levels for compositions with excess Ti deviate from the minimum position to high energies with the increase in excess Ti.
Magnetic susceptibilities were observed over the composition range from TiS2.00 to TiS1.82. They are paramagnetic and their temperature dependence is extremely small. The Pauli paramagnetism of the conduction electron gas contributes mainly to the magnetism of the TiS2 phase. From the relation between the observed magnetic susceptibilities and concentrations of excess Ti, it is concluded that the Fermi levels for compositions near the stoichiometric TiS2.00 are in the neighbourhood of the minimum position of the N(E) curve, but in a range of Ti concentrations higher than TiS1.90 the Fermi level deviates from the top of valence band, and hence the density of states is approximeted by a relation N(E)∝E1⁄2.View full abstractDownload PDF (2505K) -
Iwao Hagiwara1970 Volume 34 Issue 7 Pages 772-773
Published: 1970
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (622K)
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