Microstructures of columnar grains of uranium dioxide grown under the temperature gradient —sintered pellets, swaged compacts and vibratory compacts— below the melting point have been studied by optical and electron micrography.
The main results obtained are as follows:
1. The dominant mechanism in columnar grain growth varies with porosity. The columnar grains in high density sintered pellets of 97% theoretical density are considered to be grown by the migration of grain boundary. As the porosity increases, the migration of large voids plays a dominant role in the columnar grain growth.
2. In addition to lenticular voids, voids or gaps along the grain boundary of columnar grains are observed in porous specimens.
3. As for the powder compacts of the same composition and different compact densities, the size and number of lenticular voids increase with decreasing density.

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Four years ago the present authors discovered a new magnet alloy “Malcolloy” having a high coercive force, and determined the effect of nickel additions on its properties, the highest coercive force thus obtained being 1500 Oe. In this paper, the effect of molybdenum addition on the properties of Co–Al alloys, has been studied and found that the coercive force of the alloys increases generally by the addition of molybdenum: An alloy containing 80.51% cobalt, 13.96% aluminium and 5.53% molybdenum shows a coercive force of 1600 Oe, a residual magnetic flux density of 2750 G and maximum energy product of 1.34×10⁶ G·Oe, when tempered at 600°C for 20 hr after water-quenching from 1380°C. These alloys consist of many ferromagnetic elongated particles about 400 Å in mean diameter which are dispersed in the matrix of a nearly nonmagnetic β′ phase. Therefore, it may be concluded that the high coercivity of these alloys is mainly due to the presence of the fine particles of a single magnetic domain.

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The magneto-elastic interaction between dislocations and a 180° domain wall in a ferromagnetic material has already been investigated and the initial susceptibility has been expressed as a function of dislocation density. In this study, the initial susceptibility was measured at room temperature for nickel single crystals plastically deformed in tension. The dislocation density estimated from these experiments is found to be in quantitative agreement with other experimental and theoretical results for the stage I of the shear stress-strain curve. In the stage II, however, it does not agree with them, unless the change of the magnetic domain structure in a heavily deformed state is taken into consideration. Further, at 90° and 150°C where the magnetic anisotropy of nickel approaches zero, the influence of the shear stress on the initial susceptibility χ₀ was studied. As the results of these experiments, it becomes evident that the inverse initial susceptibility χ₀⁻¹ varies linearly with the shear stress in both stages I and II, and its slope in the stage I is about 50% larger than that in the stage II.

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Saturation magnetization and coercive force of Alnico 5 and other magnet alloys with similar compositions are measured at elevated temperatures by means of an astatic magnetometer. The I-T curves obtained reveal that these alloys consist of two kinds of ferromagnetic phases, α₁ and α₂, after appropriate heat-treatment. It is found that Curie point of the less ferromagnetic phase α₂ changes considerably with aging temperature. These results are also discussed from the standpoint of an equilibrium diagram and the phase relation. Each of the H_c-T curves obtained shows a striking maximum at a certain temperature, which corresponds to the Curie point of the α₂ phase contained in the alloy. Particularly for a commercial alloy of Alnico 5 aged at about 600°C, the Curie point of the α₂ phase lies in the neighbourhood of room temperature, so that a maximum value of the coercive force can conveniently be obtained at room temperature. Furthermore, a theoretical approach is proposed to estimate the coercive force for such a two-phase alloy. This may satisfactorily explain the characteristic feature of the observed H_c–T curve, and may elucidate that the coercive force of Alnico 5 largely depends upon the magnetization of the less ferromagnetic matrix.

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The dynamic deformation behaviour of aluminium single crystals (99.99% purity) was investigated by compression tests at room temperature using a bar-bar type impulsive loading apparatus. The dynamic stress-strain relation at strain rates of the order of 10² sec⁻¹ shows a similar orientation dependence to the static one. Crystals properly oriented for single slip under dynamic deformation show higher critical resolved shear stresses and more extensive easy glide regions than those under static deformation. The values of the critical resolved shear stresses for dynamic deformation range from 250 g/mm² to 500 g/mm². The rate of work hardening of stage II is shown to be higher for the dynamic deformation than for the static one. Microscopic observations on slip markings reveal that the dynamically deformed specimens have slip bands which are higher in density and weaker in contrast than the statically deformed ones.
On the basis of the above results, it is pointed out that for the easy glide region of deformation at high strain rates the frictional stress acting on moving dislocations becomes too large to be negligible and contributes greatly to the critical resolved shear stress and the flow stress.

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Sliding at grain boundary and shear of zone near grain boundary during a constant rate heating under various constant shear stresses of 10,000 g/sq.cm to 40,000 g/sq.cm were measured in high-purity aluminium bicrystals (99.999%) with a boundary misorientation angle of 26 deg. The amount of grain-boundary sliding increased with increasing shear stress up to 20,000 g/sq.cm, but when the stress increased to 30,000 g/sq.cm or 40,000 g/sq.cm, the amount of grain-boundary sliding became smaller than that for the shear stress of 20,000 g/sq.cm. A plot of the logarithm of the amount of grain-boundary sliding per unit temperature interval versus the reciprocal of absolute temperature was found to lie on a series of a straight line over the lower temperature range. This relationship was discussed by the relation between the amount of grain-boundary sliding per unit temperature interval and the rate of grain-boundary sliding, derived by the present authors. The activation energy thus obtained was 10,500 cal/mol for the test conducted in vacuum. According to the microscopic observation, grain-boundary sliding was found together with zone shear, but not vice versa.
In a macroscopic observation on the specimen heated up to 300°C under the constant shear stress of 30,000 g/sq.cm, a polygonized structure was found within a band region adjacent to the boundary. The formation of voids due to grain-boundary sliding was observed in original boundary, and their numbers were dependent upon the amount of sliding. These voids obstructed grain-boundary migration in the process of grain-boundary sliding.

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Using the high-purity aluminium bicrystal (99.999%) which has the boundary misorientation angle of 36 deg, observation was made of the behavior of deformation on the grain-boundary and in a narrow region adjacent to the grain-boundary during high-temperature (isothermal) shear test. The high-temperature shear test was carried out in the temperature range of 160°C to 300°C. Grain-boundary sliding (shear) was observed to occur without inducing deformation of the component crystals, accompanied by the localized deformation in a region adjacent to the grain boundary. Measurements were made of the grain-boundary sliding (shear) as a function of shear stress during the test. From the data, the grain-boundary sliding versus shear stress curves were obtained for given temperatures, and a plot of the logarithms of the slopes of the curves versus the reciprocal of shear stress resulted in a series of straight lines. The relationship was discussed by the rate equation. Grain-boundary sliding was found together with zone shear, but not vice versa. Voids were produced by the grain-boundary sliding, and obstructed grain-boundary migration.

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Typical magnesium electrolytes such as Dow, I.G., and present electrolytes with additives of sodium chloride, potassium chloride, and calcium chloride have been studied for determining the density and electrical conductivity.
The devices have been developed for determining these objectives.
The densities in these electrolytes change linearly with temperature and the electrical conductivities are expressed as the function of temperature. It has been concluded the composition of 15% MgCl₂, 30% CaCl₂, and the remainder of NaCl is advantageous as the magnesium electrolyte from the points of view of density and electrical conductivity.

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After cooling at various rates from 900°C or the subsequent heating at various temperatures below the order-disorder transformation temperature, the magnetic properties of ferromagnetic nickel-manganese alloys have been measured at room temperature with the ring-form specimens punched out from the plates, and the relation between magnetic permeability and order-disorder transformation of Ni₃Mn (23.78 wt% Mn) has been investigated. It has been found that the initial and maximum permeabilities become larger as the cooling rate decreases or the subsequent heating temperature increases : the initial permeability vs. composition curve shows only one maximum, and the maximum permeability vs. composition curve, two maxima. The alloy containing 21.91% manganese shows the highest initial permeability of 6860 when heated at 380°C for 50 hr after cooling at a rate of 10°C/hr from 900°C and the alloy with the composition of 22.00% manganese attains the highest maximum permeability of 20,400 when heat treated similarly : the former has a magnetic hysteresis loss of 18.3 erg/cm³/cycle (Bmax=2000 G), a coercive force of 0.031 Oe and a specific electrical resistivity of 60.7 μ Ω-cm at 20°C. Moreover, these alloys can be forged and rolled more readily than Permalloy and are therefore named “Nimalloy” because they are the alloys of nickel and manganese.

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The present authors previously made a study on the relation between magnetic permeability and order-disorder transformation (Ni₃Mn) in ferromagnetic nickel-manganese alloys and found a new high-magnetic permeability alloy “Nimalloy”.
Further experiments on the effect of addition of iron on Nimalloy have revealed that the alloys containing 19.37% manganese and 4.36% iron, and 19.33% manganese and 4.55% iron have an initial permeability of 39,200 and a maximum permeability of 213,000, when cooled at a rate of 26°C/sec from 600°C: The former shows a magnetic hysteresis loss of 5.40 erg/cm³/cycle, a coercive force of 0.0042 Oe for the maximum induction of 2,000 G, and a specific electrical resistivity of 68.5 μ Ω-cm at 20°C.

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Spectrophotometric Determination of Microamounts of Nitrogen in Iron and Steel with the Organic Solvent Extraction. A spectrophotometric determination of nitrogen with the organic solvent extraction was studied, and it was found that blue coloured compounds of nitrogen with phenol and sodium hypochlorite were completely extracted with isobutyl alcohol only by use of a salting-out reagent. Various conditions for the determination were also examined to decide the optimum condition. By applying the results obtained by the fundamental experiments, a procedure for the determination of nitrogen in iron and steel was established as follows: After the dissolution of the sample with hydrochloric acid, nitrogen is separated by the steam distillation procedure. The solution is neutralized with sodium hydroxide, to which phenol and sodium hypochlorite are added. 10 minutes later the solution is saturated with sodium chloride and the coloured compound is extracted with isobutyl alcohol. Nitrogen is determined by the measurement of absorbance of the isobutyl alcohol layer at 660 mμ. The method can be used successfully for the determination of up-to 0.2 μg nitrogen in iron and steel and requires about 20 minutes.

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The ageing characteristics of the Cu–Be–Al ternary alloys, containing 9∼11 at% Be and 6∼9 at% Al, were studied by means of hardness and tensile tests, optical and transmission electron microscopy, X-ray and electron diffraction, and calorimetric measurements. The investigation was done mainly on the specimen containing 9.07 at% Be and 9.05 at% Al, which was initially quenched from 800°C, where the two phases (α and β) are in equilibrium, and then aged at 340°C for various periods. The changes in various properties during ageing were due to the precipitation in the α phase and the decomposition of the β phase, both of which terminated in the equilibrium state, (α+γ). The most hardened state attained by 1.5 hr ageing was attributed to the formation of G.P. zones in the α phase and the decomposition of the β phase into the α and intermediate phases. The crystallographic orientation relations between the matrix and these phases in the course of the ageing process were determined. Finally the age-hardening of the alloys was briefly discussed.

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