The sub-structure of martensite in a quenched Ti-6 wt% Mo alloy has been investigated by means of transmission electron microscopy; microhardness and X-ray measurements have also been made. The results are as follows:
(1) In X-ray and electron diffraction patterns of the quenched specimens, there were spots due to the α′-phase (hcp), but no spots due to the β-phase (bcc) or ω′-phase (hexagonal) were observed.
(2) In the quenched specimens, needle-shaped markings seen in the optical micrographs were found to be a banded martensite (α′-phase) by transmission electron microscopy. Besides, a large number of small lenticular martensite plates, which occupied the greater part of the specimen, were observed between the banded martensite plates.
(3) Lattice defects in the banded martensite were {10\bar11} transformation twins and dislocations on (0001) planes. There were two kinds of the banded martensite; one contained only dislocations and the other dislocations and transformation twins. The latter was more frequently observed than the former.
(4) The lattice parameters of the martensite in Ti-6% Mo alloy, a=2.92₈, c=4.66₅, c⁄a=1.59₃ were obtained by X-ray measurements.

View full abstract

The thermal behaviors of the Japanese colloidal earth available as the source material in the direct reduction of aluminium were investigated by means of thermobalance, differential thermal analysis, X-ray analysis, infrared spectrum and nuclear magnetic resonance. The colloidal earth was found to be amorphous by X-ray analysis and contained 15∼30 percent moisture.
The greater part of the moisture was removed at 100°∼250°C and the moisture was found to be the physically combined water located in cavities of particles or lattice layers. The residual moisture was clearly detected by infrared spectrum even at 900°C and was inferred to be the water combined on the surface of lattice layers and crystal water.
With the advance of heating and dehydration, the infrared absorption spectrum of O–Al–OH binding was weakened, and the strengthening of Si–O and the formation of Si–O–Al binding were observed at temperatures over 500°C. The result shows the preparatory process for the separation of SiO₂ and the formation of mullite from the psudometakaoline structure, and this was evidenced by the exthothermal peak found at about 950°C by differential thermal analysis. Moreover, this exthothermal peak was derived from the nucleation of mullite, and clear needle-like crystals of mullite were observed over 1200°C.

View full abstract

The thermal behaviors of bauxites used as the source materials in the direct reduction of aluminium were investigated.
By the microscope observation under cross Nicols, it was found that the texture of the Australian bauxite is composed of finer gibbsite crystals than the Bintan and Sematan bauxites, and also that the outer skin of the Australian ore particles and the smaller ore particles are rich in boehmite content. According to the thermobalance analysis, every sample has a small amount of adsorbed water. The change of gibbsite was mainly due to the formation of χ-Al₂O₃, and less than 20% of gibbsite was transformed to boehmite, and above 1000°C the whole sample changed to α-Al₂O₃.
From the decrease in intensity of infrared absorption and nuclear magnetic resonance, an indication of decomposition of gibbsite was found in the samples heated for 1 hr at 110°C. In addition, the free water due to decomposition of the O–H group was detected in 1600 cm⁻¹ of infrared absorption and 1 gauss of nuclear magnetic resonance, and a larger quantity of the free water was found in the samples heated at 310°C for 1 hr than in those treated at 110°C.
This free water was assumed to be a solvent which takes part in dissolution and precipitation during the transformation of gibbsite to boehmite.
Furthermore, a small quantity of water was still found in the sample calcined at 700°C due to the well-developed gibbsite crystal in the Bintan bauxite.

View full abstract

The mechanism of ridging formation in 17%-chromium stainless steel sheets was studied and a model was proposed. The characteristic surface relief due to ridging was well explained by the model; shear strains caused by tensile deformation in crystals oriented with [011] parallel to the rolling direction. The presence of crystals with such orientations was confirmed experimentally. Although ridging has been believed to be formed only by deep drawing or tensile deformation of annealed sheets, it was observed even on the surfaces of cold-rolled sheets in the present study.

View full abstract

A stress-strain curve has been determined to investigate the mechanism of stress-corrosion cracking in the brass-ammonia system in reference to the role of the surface film. The corrosion behavior of surface slip lines produced in a intergranular cracking environment and the fracture surface have also been examined using optical and electron microscopes.
In the intergranular cracking environment both stress and strain required to cause failure showed larger values than those in the transgranular cracking environment. This was explained in terms of a concept that a tarnish layer is formed on the specimen surface in the intergranular cracking environment and the layer arrests the movement of surface dislocations. From the observations of the slip lines and fracture surfaces, it was concluded that the mechanism of stress-corrosion cracking varies depending on the strain rate or stress level in a constant load test.

View full abstract

The mechanism of stress corrosion cracking of α-brass is examined by using single- and bicrystals prepared by Bridgman’s technique in ammonical vapour. Plastic deformation is necessary for the initiation and propagation of cracks. The dissolution of emergent ends of dislocations is nearly independent of stress corrosion cracking. The role of a corrosive environment seems to weaken the binding force of the material by absorption or adsorption.

View full abstract

Main properties of various WC–TiC–TaC–10%Co cemented carbides have been investigated relating to the carbon content. Specimens were vacuum-sintered at 1400°C for 1 hr. The carbon contents of the alloys were strictly controlled. Properties such as lattice parameters of γ (binder) and β_t (WC–TiC–TaC triple carbide) phases, hardness, transverse-rupture strength, etc. were measured relating to the carbon content as well as titanium carbide and tantalum carbide contents.
The results obtained were as follows: (1) The composition of the γ phase and the carbon content of the β_t phase showed regular changes according to the variation in the carbon content, as have been observed in WC–Co, WC–TiC–Co, WC–TaC–Co alloys, etc.. (2) The carbon content of the β_t phase nearly attained the stoichiometric value, when the tantalum carbide content in the β_t phase exceeded about 50%. (3) The (WC+β_t+γ) three-phase region was extended mainly with increasing titanium carbide content. (4) Other various properties changed regularly with the carbon content. The most excellent mechanical properties were exhibited in high carbon three-phase alloys, in particular, in the alloys having the β_t phase with the composition of 50∼60% tantalum carbide.

View full abstract

Following the discovery of new magnet alloy “Malcolloy” of high coercivity in the Co–Al system, the present authors have made a series of experiments on the effect of the addition of nickel, molybdenum, titanium and vanadium on properties of Co–Al alloys, and obtained the highest coercive forces of 1450∼1600 Oe. Further, they have found that the coercive force and the maximum energy product of Co–Al alloys are generally increased by the addition of chromium: An alloy composed of 82.11% Co, 14.12% Al and 3.77% Cr shows the coercive force of 1450 Oe, the residual magnetic flux density of 3150 G and the maximum energy product of 1.42×10⁶ G·Oe when tempered at 550°C for 15 hrs after water-quenching from 1375°C. The highest maximum energy product among all the alloys studied is 2.40×10⁶ G·Oe. Such high-coercivity alloys consist of many elongated particles of a ferromagnetic phase, about 300 in diameter, dispersed in the matrix of a nearly nonmagnetic β′ phase, from which it is apparent that their high coercivity is mainly due to the presence of the fine particles of a single magnetic domain.

View full abstract

Since their discovery of high magnetic permeability alloy “Nimalloy” in the Ni–Mn system, the present authors have made a study of the effect of the addition of iron on its properties, and obtained the highest initial permeability of 39200 and the highest maximum permeability of 213000. According to the results of the present experiment, the initial and maximum permeabilities of Ni–Mn alloys are generally increased by small vanadium additions. An alloy containing 19.92% manganese and 2.16% vanadium, which was cooled at a rate of 240°C/hr from 900°C and reheated at 420°C for 95 hrs, shows the initial permeability of 22000, the maximum permeability of 169500, the magnetic hysteresis loss of 4.47 erg/cm³/cycle and the coercive force of 0.0095 Oe for the maximum induction of 2000 G, and the specific electrical resistivity of 55.3 μΩ-cm at 20°C.

View full abstract

WB₂ and TaB₂ dispersives in UO₂ were heated in flowing steam and in static high-pressurized steam, and the reaction between steam and borides was studied by means of the X-ray diffraction method and optical microscopy.
The main results obtained are as follows:
(1) Powder compacted specimens of UO₂–WB₂ and UO₂–TaB₂ reacted with the flowing steam at 600°C. WO₂ and H₃BO₃ were formed for UO₂–WB₂, and Ta₂O₅ and H₃BO₃ for UO₂–TaB₂. It was considered that the boron element migrated out of specimens in the form of a gaseous compoud. There were no reactions between UO₂ and borides in steam.
(2) In the sintered pellet specimen of UO₂–WB₂, there were no appreciable changes in the shape and location of the WB₂ particles even after heating at 600°C, while in the UO₂–TaB₂ specimen a new phase, which was considered as Ta₂O₅, appeared in the annulus region surrouding each TaB₂ particle after heating at 600°C, although no appreciable migration of TaB₂ particles was observed.
(3) The effect of pressurizing of steam on the behaviors of UO₂–WB₂ and UO₂–TaB₂ was not recognized in the temperature range below 400°C.

View full abstract