In order to determine continuously the austenite grain size of steels with a high temperature microscope, observations of the austenite grain growth of 0.2% C steels (Si–Mn killed, or Al killed) in various atmospheres were carried out. The results obtained were as follows:
(1) When 0.2% C steels were heated in 3×10⁻⁵ mmHg vacuum, the austenite grains on the surface were coarsened remarkably to ASTM No.2 at 950°C, and their grain size was markedly different from that in the inner zone.
(2) When these steels were heated in extremely pure argon atmosphere in the pressure range of 0.6∼1.0 atm, the austenite grains on the surface maintained a grain size of ASTM No. 8 up to about 1150°C, and then coarsened. The value of their grain size was nearly equal to that of the inner grains.
(3) According to an electron microscopic study, the degree of oxidation on the specimen surface in high vacuum was less than that in argon. Therefore a high vacuum was replaced with the argon atmosphere at 950°C or 1000°C, but no changes in grain size were observed.
(4) As regards the surface grain growth of 0.2% C steels in various atmospheres, it was observed that the lower the degree of vacuum or the higher the argon pressure, the higher the grain coarsening temperature.
(5) Remarkable grain growth which occurred at about 950°C in high vacuum was also observed at the specimen surface several microns in depth even after removing the mechanically polished layer by electrolytic polishing.

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Influences of ten kinds of less than 0.5 at% additional elements on the aging kinetics of Al–2.5 at% Zn and Al–2.5 at% Zn–2 at% Mg base alloys have been studied from the measurements of electrical resistivity and hardness and also electron microscope observations, and the mechanism is discussed with particular attention to the role of lattice defects.
The results are as follows:
(1) The rate of pre-precipitation in Al–Zn and Al–Zn–Mg alloys is reduced by the additions of Si, Sn (group a), Fe, Cr, Mn, Zr, V (group b) and Cu, Cd (group c), but is enhanced by Ag.
Precipitation hardening of Al–Zn–Mg alloys is also reduced by the additions of groups (a) and (b), but is increased by the pre-aging at low temperatures or by the additional elements of group (c) and Ag.
(2) The effect of group (a) may be interpreted from the fact that both elements have a larger binding energy with a vacancy than that between a Zn atom and a vacancy, and that they do not interact with Zn atoms but form intermetallic compounds with Mg atoms alone.
The effect of group (b) can be reasonably explained in terms of the increase in crystal defects such as dislocations, subboundaries, grain boundaries and insoluble compounds formed by these additional elements, whose boundaries act as vacancy sinks to reduce the concentration of quenched-in vacancies, rather than the existence of the binding energy between the solute atom and a vacancy.
Ag and the elements of group (c) participate in the formation of G.P. zones which act as the heterogeneous nucleation center for the fine M’ (MgZn₂) phase, resulting in the increase in the age-hardening of Al–Zn–Mg alloys at higher temperatures. In particular, the addition of more than 0.03 at% Ag also increases the rate of clustering of Zn and Mg atoms as well as the number of zones; this phenomenon is explained by the faster clustering rate of Ag atoms than that of Zn and Mg atoms during the quenching and the subsequent aging.

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A transmission electron microscopic investigation has been carried out on the interaction between dislocations and precipitates in thin foils of an aged aluminium alloy containing 1.36 at% silicon. From the measurement of the radius of curvatures of moving dislocations expanded between precipitates, the stress acting on the dislocations has been determined for several stages of ageing. The result shows that the dislocations cut through the small pecipitates at an early stage of ageing. In the over-aged state, however, the by-pass process, formation of dislocation half-loops around the precipitates lying near the surface and loops sorounding several precipitates, prismatic dislocation loops due to double cross slip and tangling of dislocation around large precipitates have been directly observed. Comparison with the observations on the thin foils which were prepared from stretched bulk materials shows that these phenomenon might also occur in the bulk materials.

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This study has been carried out in order to clarify the interactions between metals and molten salts. As one of the basic studies on mixtures of metals and molten salts, the results of thermal analyses and measurements of electrical conductivities of salt-rich solutions of tin in molten bismuth trichloride are reported in this paper. For this system, when tin is dissolved in molten bismuth trichloride, the reaction is expected to proceed according to 3Sn+2BiCl₃=3SnCl₂+2Bi. Bismuth so produced, however, is known to dissolve in molten bismuth trichloride. The solution, therefore, is considered to be a mixture of stannous chloride and bismuth-bismuth trichloride. Thermal analyses were carried out by means of the ordinary cooling curve method to find the monophase regions. For the region ranging from pure salt to ca. 20 mole% metal, the electrical conductivity was measured by means of the capillary cell method with an alternating current over a temperature range from 240° to 400°C under argon atmosphere. With increase in tin content, the specific conductivity increased until it attained a maximum and then decreased at every temperature. As the metal content further increased, this system again showed an increase in conductivity. These results were compared with those of the bismuth-molten bismuth trichloride system, and it was found that at low metal concentrations the mechanism of the conductance of the tin-molten bismuth trichloride system was similar to that at the higher temperature side of the bismuth-bismuth trichloride system. This was explained by the presence of a simple ion or monomer in the tin-bismuth trichloride system.

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The effect of ausforming on the strength, ductility and hardness of several typical tool steels containing high carbon and high alloying elements were examined by static bending and hardness tests. The results obtained were as follows: (1) In tool steels containing high carbon and high alloying elements, there was a tendency that the increase in ductility by ausforming was more remarkable than that in strength, and the effect of ausforming varied with alloying elements in steels. (2) The effect of ausforming was hardly observed in the steels containing only chromium, but in the steels containing molybdenum, vanadium, tungsten, etc. which caused secondary hardening by tempering, the effect was remarkably observed in both strength and ductility. The 50%-ausformed SKH 9-steel (W-Mo high speed steel) had a maximum bending stress of 400 kg/mm², a yield strength of 300 kg/mm² and an absorbed energy of 750 kg-mm which was about 7 times as large as that of the unausformed steel. (3) The unausformed steel containing Mo, V, W, etc. showed a hardness drop at tempering temperatures of 300∼400°C and then a secondary hardening by tempering at about 500°C, whereas the hardness drop observed at 300°∼400°C came to disappear with the increasing degree of ausforming and retained a high hardness level throughout the tempering temperature range. (4) Optical micrographs showed that there was no remarkable difference between the ausformed and unausformed specimens, except for cracking of primary carbides which had already existed at the austenitizing temperature.

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The temperature dependence of equilibrium partition of alloying elements between ferrite and cementite was determined for several steels. After tempering the quenched steels for varying times at various temperatures, carbide was isolated electrolytically and the alloy contents in the carbide were determined. The equilibrium manganese, chromium and molybdenum concentrations in cementite, C_e, decreased with temperature and its temperature dependence was expressed by the following equation:
C_e=Aexp(B⁄T), wt%
A, B: constants, T: temperature, °K
The distribution coefficient, C_e/C_o (C_o : equilibrium alloy concentration in ferrite), was relatively insensitive to the coexistence of other alloying elements and to the carbon content in steel. The tempering time required for the equilibrium state and its dependence on the carbon content in steels and their initial structures before tempering were also investigated.

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The process of formation of the cube recrystallization texture in a pure copper sheet cold rolled by 93% was examined mainly by using a transmission electron microscope, with the following results: (1) On annealing at 150°C small recrystallized grains appeared within about 30 sec in the deformed matrix similar to that after rolling. Their size was larger than about 1 μ. The growth rate of the small recrystallized grains was high. (2) That most of the recrystallized grains more than 2 μ in diameter had cube orientations was recognized based on electron diffraction and the shape of annealing twins. (3) The recrystallized grains were aligned along straight lines parallel to the rolling direction. The orientations of the areas on both sides of the line were different from each other. The relative orientation relationships were not definite. (4) No recrystallization occurred preferentially in the regions with cube orientations which had been produced by rolling. (5) Recovery proceeded in the deformed matrix simultaneously with recrystallization. The cube recrystallized grains grew rapidly at the expense of the recovering deformed matrix.
These facts seem to support that the cube recrystallization nuclei are formed by a particular mechanism such as the inverse Rowland transformation, although no direct evidence for the occurrence of such a mechanism can be obtained under the resolving power of the electron microscope.
The rolling and annealing textures of all fcc metals and alloys can be classified according to the magnitude of the stacking fault energy (γ) of the material and the degree and temperature of deformation. In copper, gold and nickel, having moderate values of γ, the fraction of {112}⟨111⟩ twin components is high after heavy rolling at room temperature and the cube texture is formed after subsequent annealing.

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Aging behaviors of Cu-Ti alloys containing 0.6, 1.0 and 3.0 wt% Ti were observed by transmission electron-microscopy in the course of isothermal aging at 500°C and 700°C (for only 3.0 wt% Ti alloy). In the early stage of aging, coherent spherical particles appeared in the matrix and gradually grew into bamboo leaf-like precipitates grouped in parallel (all of which were smaller than 1 μ) with the aging time. But the degree of their growth differed by the titanium compositions and aging temperatures. The traces of the precipitate particles coincided with the ⟨100⟩ and ⟨110⟩ directions in the matrix, whereas the habit plane was parallel to {100} in the matrix. The results of microscopic observations were also compared with the side bands structure in X-ray diffraction and the characteristic change in electrical resistivity observed previously.

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In order to investigate the dynamic deformation behaviour of annealed polycrystalline aluminium at room temperature, its dynamic stress-strain curves at high strain rates (10²∼10⁴ sec⁻¹) were obtained using a bar-bar type impulsive loading apparatus. In this experiment, a cylindrical specimen was inserted between two elastic bars and compressed rapidly by transmitting a stress pulse generated by the impact of a bar.
The dynamic stress-strain curve is parabolic in a way similar to the static curve. The dynamic flow stress is always higher than the static one showing strain rate dependence. From the results obtained at higher strain rates the stress-strain-strain rate relationship is summarized by an equation
σ(kg⁄mm²)=12.8·ε^0.38·\dotε^1⁄16(sec⁻¹).
It is concluded from the results that the flow stress depends not only on the instantaneous strain and strain rate but also on the strain rate history of the specimen.

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Anodic behaviors of pure iron and iron oxides in dilute sulfuric acid and alkaline solutions were investigated to clarify the significance of passivation and other oxidizing potentials of iron. The anodic polarization curve of pure iron indicated four current peaks at potentials of about −0.1, 0.3, 0,6 and 1.4 V in 1 N H₂SO₄ and −0.9, −0.7, −0.4 and 0∼0.4 V (vs S.C.E.) in 1 N KOH. The anodic polarization curves of FeO_1.05, FeO_1.1 and Fe₃O₄ indicated three, two and one peaks, respectively, and the potentials of the peaks of the oxides agreed with those of pure iron. From these anodic behaviors of the oxides, it was suggested that the four potentials at the current peaks in the potential-current curve of iron show four redox potentials of Fe/FeO_1.05, FeO_1.05/FeO_1.1, FeO_1.1/Fe₃O₄ and Fe₃O₄/γ Fe₂O₃, where FeO_1.05 and FeO_1.1 are two Wüstites containing minimum and maximum combined oxygen, respectively. These potentials were also confirmed from the measurements of potential decay curves of iron and iron oxides. From these results, it was concluded that the passivation potential of iron in 1 N H₂SO₄ corresponded to the redox potential of FeO_1.05/FeO_1.1, whereas that in 1 N KOH corresponded to the redox potental of Fe/FeO_1.05.

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The present authors measured the magnetic properties of cobalt-rich Co–Al alloys and discovered a new magnet alloy “Malcolloy” which has a high coercive force of 1200 Oe. In this paper is further studied the effect of nickel addition on their properties, with the following results. The coercive force of Co–Al alloys is usually increased by the addition of nickel: The alloy containing 65.46% cobalt, 14.74% aluminium and 19.80% nickel shows a coercive force of 1500 Oe, a residual magntic flux density of 3200 G and a maximum energy product of 1.45×10⁶ G·Oe when tempered at 525°C for 15 hours after water-quenching from 1370°C and is forgeable at high temperatures. These alloys consist of many elongated ferromagnetic particles about 200∼1000Å in mean diameter dispersed in the matrix of nonmagnetic β phase. Consequently it may be concluded that the high coercivity of the alloys is caused mainly by the presence of the aforementioned fine particles of a single magnetic domain.

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A rapid electrographic determination of magnesium in magnesium-aluminum or magnesium-nickel alloys and zirconium in zirconium-nickel alloys was worked out. The method consisted of the stripping of alloy constituents into a filter paper moistened with a supporting electrolyte solution and the subsequent measuring of the intensity of color developed on the paper spectrophotometrically. Suggested electrolyte solutions were 0.5 M sodium potassium tartrate for magnesium alloys and 0.5 M NH₄Cl for zirconium alloys. After electrographic stripping (4 V, 10 mA, 10 sec for magnesium and 20 sec for zirconium) of the alloy constituents into the filter paper under a pressure of 2 kg per 6.25 cm², the filter paper was treated with a saturated ethyl alcohol solution of quinalizarin for magnesium and with an ethyl alcoholic solution of 0.5% alizarin for zirconium to develop the colored pattern to be measured at 560 mμ and 510 mμ, respectively. The method seems to be of special value for a rapid and practically non-destructive determination of magnesium and zirconium in their alloys.

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