The cobalt phase purity in hard alloys was examined by the X-ray diffraction method and the Curie point was measured. It was found that fairly large amounts of various atoms could be dissolved in cobalt and that the purity at high temperature depended largely upon the alloy carbon content.

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The course of transformation of 0.68% carbon steel after rapid heating to austenizing temperatures has been investigated using hardness measurements, microscopic and dilatation techniques. The steel specimens used for the investigation have lamellar with, and spheroidized pearlites and a structure consisting of spheroidized pearlite with graphite nodules. The austenizing curves obtained from the hardness measurements of spheroidized specimens show a sigmoid shape, on the other hand, austenizing for lamellar specimens is completed more quickly after a certain incubation period. The explanation of the time required to complete the transformation for the structural variables as a function of ferrite-cementite interfacial area is not sufficiently conclusive.

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Carbides isolated electrolytically from molybdenum steels, heat-treated at 700° or 900°C, have been examined by X-ray, chemical, and thermo-magnetic analyses, and by electron-microscopic observations, with the object of elucidating the nature and occurrence of carbides in molybdenum steels, and to determine the carbide phase diagrams of molybdenum steel, below and above the eutectoid temperature. Five kinds of carbides, M₃C, M₂₃C₆, ξ, M₂C and M₆C have been found in molybdenum steels. These carbides have been classified into three groups according to their stability, (i) M₃C, ξ and M₆C are stable carbides, (ii) M₂₃C₆ is a metastable carbide, and (iii) M₂C is intermediate one. The chemical composition and the crystal structure of these carbides have been determined as follows;
M₃C : orthorhombic, 6.67%C, 0 to 2%Mo
M₂₃C₆ : face-centered cubic, 5.0 to 6.0%C, 6.0 to 13.0%Mo
ξ : probably orthorhombic, 5.5 to 6.0%C, 25 to 37%Mo
M₆C : face-centered cubic, 2.5 to 2.8%C, 45 to 62%C
M₂C : hexagonal, about 6.0%C, 70%Mo.

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The oxidation reaction of zirconium in air was studied in the temperature range 650°∼850°C. The reaction was followed up by measurements of weight change, chemical analyses of nitrogen absorbed in the oxidized specimens, and electron microscopic observations of the surface and cross-section of specimens. Above 750°C, a significant breakaway phenomenon in the oxidation rate was observed, and the rate changed from an initial cubic or parabolic law to a linear one. Analyses of nitrogen indicated that the absorbed nitrogen, concentrated in the metal phase near the metal/oxide interface, could not be stable in the post-break away stage. The results of electron microscopic observations indicated that the cracking in the inner oxide layer did have a correlation with the change in kinetics, but the cracking at the surface had no correlation to it. Electron micrographs of cross-sections also showed that the metal phase near the oxide layer had a greatly different appearance in structure in the post-breakaway stage from that in the initial stage. The mechanism of heavy break-away phenomenon in oxidation zirconium in air was discussed on the basis of the observations in electron micrographs with emphasis on the function of nitrogen.

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The influence of bath composition and current density on the crystal structure, microscopic structure, W content, hardness and current efficiency of W-Co deposits obtained from a tartrate bath was studied. The W content, the microscopic structure and the crystal structure of W-Co deposits were correlated with one another and could be classified into three groups with the increase of the W/Co weight ratio in a plating solution and current density. The three groups were as follows: Group (A) 20 to 35 wt% W, angular microscopic structure, preferred orientation of a hexagonal α Co solid solution exhibiting the (10\bar10) or the (10\bar11) plane being parallel to the surface; Group (B) 36 to 42 wt% W, intermediate microscopic structure, preferred orientation different from that in group A; Group (C) 43 to 52 wt% W, granular microscopic structure, diffused X-ray diffraction pattern in the range of d=2.25 to 1.89 Å. The cause of this diffuseness of the diffraction lines observed in high W deposits may be explained in terms of the increase of strain in an α Co lattice due to the supersaturation of the W atoms in the lattice.

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The hardness of a W-Co electrodeposit obtained from a tartrate bath is abnormally increased when it is heated at 700°C for 1 hour. The hardening process of W-Co deposits which were produced under various plating condition was investigated, and the mechanism of this hardening was discussed after the examination of the crystal structure by the X-ray diffraction method. The results obtained were as follows: It was found that the ordering transformation of α Co→Co₃W took place in the deposit during the heating, though the ordering was not completed by heating at 700°C for 1 hour. The increase in hardness was almost proportional to the W content in the deposit, except when particular plating conditions such as a low Co-content solution and high current density were used. The degree of hardening seemed to be dependent on the size, the amount and the distribution of ordering regions in the α-Co solid solution.

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The work hardening characteristics of the basal slip of magnesium have been investigated by tension test at elevated temperatures, from room temperature to 300°C, using crystals of various orientations. The resolved shear stress shear strain curves obtained typically consist of two stages. The first is the well known easy glide region, and the second is a rapid hardening region which corresponds to the so-called stage II of f.c.c. metals, but in these curves the region corresponding to the stage III of f.c.c. metals is not observed. Stage II of magnesium basal slip decreases with increasing temperature, and disappears above 200°C. From the results of tension tests and metallographical examinations, it is concluded that the hardening mechanism of basal slip in stage II is much different from that of the octahedral slip in f.c.c. metals, and it depends on the {11\bar20} kink bands locked by the formation of {10\bar12} twins.

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In a previous paper, studies of the various physical properties of molten lead silicates were reported. Observation of the effects of the structure sensitive properties of lead silicate melts resulting from addition of various metallic oxides as a third element should be of great importance in order to understand the constitution of molten silicates. As a result of the measurements of surface tension, density, viscosity, electrical conductivity and liquidus temperature, a linear relationship was found between these physical quantities and the radius of the added metallic ion or rather ionic potential Z⁄(r+r₀)² (where Z is valency of metallic ion, r and r₀ are radii of metallic and oxygen ions respectively). From the measurements of a freezing point depression of a compound of PbO·SiO₂, the heat of fusion was calculated to be about 5,000 cal per mole.

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The structure of palladium-rich solid solutions (α-phase) with a composition near 25 atomic % manganese in a palladium-manganese system has been investigated by electron diffraction using thin oriented, evaporated films, and an ordered phase, Pd₃Mn, has been found to exist in the equilibrium state below about 650°C. The structure of this phase is a periodic one-dimensional anti-phase domain structure of the Ag₃Mg type composed of cubic fundamental cells, the domain size being twice this cell. This ordered phase was not detected by previously reported X-ray studies, probably due to the long relaxation time for ordering of this phase.

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Experiments were carried out to study the effect of the second phase of metallic compounds on the “Work Softening” phenomenon in Al-Fe, Al-Si, Al-Mn and Al-Li alloys.
When particles of metallic compounds were dissolved by quenching after solution treatment so that the ingot was in the state of super-saturated solid solution or eutectics, the “Work Softening” phenomenon was not observed in the sheet obtained from this ingot.
On the other hand “Work Softening” phenomenon was observed in the sheet produced by a process of preheating the ingot followed by an intermediate heat treatment to precipitate a large amount of metallic compounds, when light rolled after final annealing at the temperature of the softening stage. The finer the precipitated particles were, the more distinctively the “Work Softening” phenomenon was observed and no connection with natural or artificial aging after light rolling.
Regarding the process of “Work Softening” phenomenon, it cannot be explained by the Cottrell mechanism. Therefore a more thorough investigation in the light of the sub-grain formation by dislocation rearrangement may be required.

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It is well known that an abnormal expansion appears in Cu-Sn compacts during sintering. In order to investigate the source of this phenomenon, the author carried out a dilatometric study on the kinetics of sintering for Cu-Sn compacts containing about 10% Sn powder and 0.5% Zn-stearate as lubricant.
In this experiment the abnormal expansion always appeared at 798°C, which is the highest peritectic temperature in the Cu-Sn system, and increased in amount with the increase of the heating rate. From the microscopic examination, it was found that just below the peritectic temperature a large amount of the liquid phase was retained in the compact coexisting with the β phase. However, just at this temperature or above the β phase should decompose into α phase and liquid phase, accelerating the diffusion rate and the following solidification.
In this way absorbed gases in the liquid phase of the compact were discharged by rapid solifidication at the peritectic temperature during sintering, a great portion of the absorbed gases can be estimated as H₂ from the atmosphere controlling examination. In order to eliminate the abnormal expansion, slow heating, isothermal keeping just below the peritectic temperature and the reduction of the Sn-content in the compact are recommended.

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