Amorphous ribbons obtained by a melt quenching method can be considered as low cost materials because of their simple manufacturing process. Iron based amorphous alloys are expected to be a good transformer core material due to their high induction and permeability characteristics. While extensive studies on the composition and heat treatment have been performed so far, few reports have dealt with magnetic properties in the as-quenched state. In this study, we have intended to study the relation between the magnetic properties in the as-quenched state and the process conditional. Samples with the composition of Fe73Ni8Si10B9 were made by a single roll quenching apparatus, and the ejection pressure, the roll rotation number and the temperature of the ribbon surface when pulled from the melt were varied. The magnetic properties were measured by a toroidal core method. The fracture strains were observed by the Bitter method. It was found that the magnetic anisotropy of amorphous ribbon became greater with higher rotation number VR. Maze patterns in the domain structure were significant at VR=33-42 s−1, but the 180° domains dominated at VR=50-58 s−1. These magnetic properties and domain structures can be explained by the compression perpendicular to the ribbon induced by Inver effect concerning the temperature of the ribbon surface when pulled from the melt.
In order to clarify the process of recrystallization, in particular, the secondary recrystallization in commercial copper, textures, microstructures and individual grain orientations have been examined by means of X-ray diffraction and scanning electron microscopy (SEM) and SEM-electron channeling pattern method. Deformation textures of copper subjected to “straight rolling”, “zigzag rolling” and “reverse rolling” were very similar to one another. However, on “straight rolling”, the primary recrystallization texture of a fine grained sample showed a sharp cube orientation, while that of a coarse grained sample took a cube orientation mixed with a random one. Secondary recrystallization probabilities were affected by the initial grain size, rolling procedure, annealing conditions and the ear produced by heavily rolling reduction. Most of the secondary recrystallization orientations obeyed Kronberg and Wilson’s rotation relationship. In addition, nearly a cube orientation was observed. On “cross rolling”, deformation, primary and secondary recrystallization textures showed (110)[\bar223]+(001), (519)[\bar4 11 1]+(110)[\bar223] and (110)[\bar223], respectively. Some grains with orientations identical to those observed in the secondary recrystallization were found in the primary recrystallization sample with sharp cube orientations. Such grains were thought to relate to the secondary recrystallization.
The electrical properties of an intermetallic compound HgTe, such as carrier concentrations Ne and Nh, and mobilities μe and μh of electron and hole, respectively, obtained from the analysis of the Galvano-magnetic effects at 4.2 K were thermodynamically associated with the annealing temperature and the partial pressure of Hg on the P(pressure)-T(temperature) phase diagram for the Hg-Te system. The P-T-X(composition) phase diagram of HgTe was drawn from the relative difference |Ne−Nh| and the intrinsic boundary was obtained from the minima of the |Ne−Nh|. Then, the i-boundary of the present work was compared with those reported previously and examined. Also, contour maps of the electron mobility μe and hole mobility μh were drawn on the P-T diagram, which was named, so to speak, P-T-μ(mobility) phase diagram and gave the condition to obtain a desired mobility. Further, the quantities α=μh⁄μe(=1⁄b) and β=Nh⁄Ne, defined in the analysis of the Galvano-magnetic effects of HgTe, were calculated and maps of distribution of these quantities were drawn on the P-T diagram. They were named the P-T-b(=1⁄a) and P-T-β phase diagram, as they represented supplementally the meaning of the P-T-μ and the P-T-X diagram. Additionally, the field of appearance or reversal of the negative or positive sign of Hall coefficient was shown on the P-T diagram, according to conditions of the temperature and the magnetic field in the measurement of Hall coefficient. This diagram is expected to become a reference or a standard to select the condition of the measurement and to estimate a conductive type etc.
The effect of the amount of cold work (from 0% to 90%) of ferrite (α)) and the aging temperature on the precipitation behavior of austenite (γ) from α during the aging in (α+γ) two phase region have been investigated using Fe-25%Cr-7%Ni-3%Mo and Fe-28%Cr-4%Ni-4%Mo (α+γ) two phase stainless steels. The starting structure of the alloys before the aging is fully ferritic. It is found that the resulting structures are remarkably affected by the amount of cold work of α, the aging temperature and the aging time. When the amount of cold work is small (<25%), the precipitation of γ preferentially occurs at α-grain boundaries and deformation bands at an early stage of aging, and then γ particles precipitate inside α-grains at a later stage of aging. When the amount of cold work of α is large (>50%), the subgrain structure is rapidly formed by recovery in α-matrix during heating up to the aging temperature or during the earliest stage of aging, and then γ particles precipitate at these α subgrain boundaries. As the amount of cold work of α increases, size of α subgrains decreases, so that the precipitated γ particles become to disperse finely and homogeneously. In particular, when the amount of cold work of α exceeds about 70%, a microduplex structure, which consists of very fine α subgrains and γ particles, is obtained. However, it is found that a recrystallization of α matrix occurs during aging when the volume fraction of precipitated γ or the size of γ particles is small, because the pinning effect of γ particles on the migration of α subgrain boundary is deduced. Therefore, it is necessary to hold a large amount of cold work of α and to precipitate the large volume fraction of γ to obtain the microduplex structure.
In previous works on the tensile deformation of fcc crystals, we have shown that stage I terminates with the formation of kink bands which are transmuted from “local bend-gliding regions” formed under the uniaxial constraint. The present paper aims at clarifying the formation process of the local bend-gliding region, and at verifying the nature of excess dislocations constituting the local bend-gliding region. Results obtained by using Cu and Cu-Ge alloy crystals are: (1) The formation of local bend-gliding regions was verified by both X-ray analysis of the specimen axis rotation in local regions and the observation of the dislocation structure revealed by etch pits. (2) The local bend-gliding regions are formed in any part of a specimen where the operation of primary main slip is inhomogeneous. (3) The presence of grown-in subboundaries enhances the development of local bend-gliding regions, leading to marked reduction of extent of stage I. (4) In highly perfect crystals with few subboundaries, the interaction of the primary slip with the secondary slip which has operated at the pre-yield stage is important for the development of local bend-gliding regions. (5) Excess dislocations constituting the local bend-gliding region generally consist of both screw and edge components. The ratio of strengths of the two components computed by the three-dimensional F.E.M. (finite element method) stress analysis agrees well with the theoretical prediction previously made by Takamura.
In order to investigate the mechanism of solid solution hardening of titanium carbide by molybdenum, single crystals of various compositions were grown by the r.f. floating zone technique and were deformed by compression at temperatures from 1270 to 2270 K and at strain rates from 5×10−5 to 7×10−3 s−1. Plastic flow behavior of the crystals was found to be clearly different among three temperature ranges—low, intermediate and high temperature ranges—whose boundaries were dependent on the strain rate. From the observed behavior, it is considered that the deformation in the low temperature range is controlled by the Peierls mechanism, that in the intermediate temperature range by the dynamic strain aging and that in the high temperature range by the solute atmosphere dragging mechanism.
Direct observation has been made of the film motion of liquid PbO-SiO2 slags on solid silica in a local corrosion zone for rod and prism specimens by the aid of motions of very small bubbles floating on the film. During the early stage of local corrosion, the slag film forms characteristic flow patterns, principally composed of wide zones of rising film and narrow zones of falling film, according to the contour of the specimen. In the range where the local corrosion progresses markedly, rising and falling film velocities were determined in relation to vertical direction, dipping time, slag composition and shape of the specimen. Films of rising zone are thinner by several times than those of falling zone. Change in SiO2 content in the solidified slag film is detected along the surface of the specimen in directions vertical to and also perpendicular to the surface. Forces participating in the film motion are surface tension gradient, gravity and pressure difference in the film. The pressure difference is caused by the difference in radius of cavature of the film surface formed along the contour of the specimen. Hydrodynamic analysis on the film motion results in good agreement between the calculated and observed film velocities. The analysis indicates an effective promotion of mass transport of dissolved component from the specimen by the active film motion in diffusion layer in the film, that is, break down of diffusion layer, which accerelates the local corrosion.
The effects of oxygen partial pressure (0.3 to 1.6 kPa) on the room temperature oxidation behaviour of sputter-deposited titanium films (58 nm in thickness) have been investigated by using a quartz-oscillator microbalance. The titanium films were sputter-deposited onto a quartz oscillator from a pure titanium target or a titanium target partially covered with TiO2 square tips under argon or argon-1% oxygen atomosphere at 1 Pa pressure. It was found that a major portion of the oxide layer (18-6×1019 O2/m2) was formed during the initial fast oxidation process and the initial oxidation rate in the low oxygen partial pressure (0.3-200 Pa), as well as the number of the oxygen sorption layer, depended on the oxygen partial pressure. However, as the oxygen partial pressure increased, the oxidation rate was almost independent of the oxygen partial pressure. The oxygen dissolved during the sputter-deposition from the target (Ti-TiO2) or from gas phase (Ar-O2) was found to decrease the initial fast oxidation rate and the number of the sorption layers. After the initial fast oxidation, the oxidation process followed a usual logarithmic rule.
The EMF method by solid electrolyte (ZrO2+9 mol%MgO) was used for the determination of the activity of FetO in CaF2-CaO-FetO (1673-1733 K) and CaCl2-CaO-FetO (1623-1673 K) systems. No appreciable effect on the FetO activity was found, when FetO was replaced by CaF2 or CaCl2 at a constant CaO content. The Fe3+/Fe2+ ratio, on the other hand, was found to increase with increasing CaF2 content and to decrease with increasing CaCl2 content at a constant CaO content.
A vacuum rheocasting technique in which a solidifying alloy is violently agitated at high speed has been applied to production of some new bearing aluminum base alloys containing 15 to 50 mass%Pb. Rheocast microstructures of Al-Pb alloys have been observed using scanning electron microscopy. Coarse lead-rich phases in them are uniformly scattered coexisting with fine eutectics between aluminum-rich primary solid particles formed by destruction of dendrites. The torque of a stirrer inserted in the vacuum-melted alloys has been continuously measured during the rotation of stirrer at a speed of 70 s−1 from the beginning to the final stage of solidification. The apparent viscosity of the semi-solid alloys is evaluated on the basis of the values of torque. The ultimate tensile strength and elongation have been investigated at room temperature and at elevated temperatures. A comparison of the mechanical properties of Al-Pb alloys with those of existing bearing alloys shows that the leaded aluminum alloy is a high cost-performance material.
The residual liquid in solidifying Cu-8 mass%Sn alloys having different shapes of dendrites was forced to flow into a tube at different fractions solid by compressing. The apparent permeability of residual liquid was calculated from the rate and pressure in Darcy’s equation. The apparent permeability is nearly proportional to the cube of fraction liquid. The interdendritic fluid flow proceeds at fractions solid within a range from 0.4 to 0.8. When slender dendrites are growing in the alloy containing Si, the range, particularly the lower limit, transfers downward and the apparent permeability reduces at the same fraction liquid. When shorter and rounded dendrites are growing in the alloy containing Fe, on the other hand, the range transfers upward and the apparent permeability increases. The apparent permeability is almost proportional to the 2.5 th power of the hydraulic radius which depends on the geometry of dendrites.
Tensile tests in the temperature range betwean 293 and 1773 K and fractography were carried out on 6×10−4 m thick specimens of Mo-0.3, 0.5, 0.75 and 1.0 mass%Zr alloys nitrided in a purified N2 atmosphere of 0.1 MPa at 1473 to 1773 K, referring to the alloys recrystallized in a vacuum at 1773 K. The nitrided samples, irrespective of solute content and nitriding temperature, underwent brittle fracture before macroscopic yielding at all test temperatures lower than 1673 K, while the recrystallized alloys showed good ductility. This embrittlement may be attributed to a high stress concentration at grain boundaries near the surface at a depth of ∼10−4 m, built up by dislocation channeling throughout the region containing very thin plate-like ZrN precipitates about 0.5 nm thick. At 1773 K, the nitrided alloys had a fairly good ductility independent of solute content. At such high temperatures, no stress concentration may occur at grain boundaries because of the ease of dissociation and climbing of glide dislocations there.
Young’s modulus, the thermal expansion and the magnetization in the temperature range of 120-670 K and the crystal structures at room-temperature were investigated for Mn-Ge base ternary alloys containing Zr or Nb less than 16% with β, γ, ε and their mixture phases. Each characteristic shows peculiar changes corresponding to the β\
ightleftarrowsε phase transformation point Tt, the Néel point of the antiferromagnetic ε-phase TN(ε) and that of γ-phase TN(γ) on each temperature variation curve. The Elinvar characteristics were obtained in the temperature range between Tt and TN(ε) and/or below the TN(γ). Invar characteristics were observed below TN(ε) for the alloys having an ε-rich phase. These ternary alloys were easily cut by a normal lathe in all of the phases, and the forgeability was excellent in the γ-phase.
Magnetic property, electrical resistivity and hardness were measured on Ni-Fe-Nb-Ta alloys containing 70.50-90.12%Ni, 5.03-19.76%Fe, 0.50-10.58%Nb and 0.52-20.50%Ta. These alloys were first heated in hydrogen atmosphere at a temperature between 1323 and 1573 K, and then cooled at various rates from a temperature above the order-disorder transformation point. The highest initial permeability of 171 mH·m−1 was obtained for an alloy containing 78.18%Ni, 11.83%Fe, 6.94%Nb and 3.05%Ta, and the highest maximum permeability 925 mH·m−1 for an alloy containing 75.26%Ni, 11.51%Fe, 3.05%Nb and 10.18%Ta when cooled at a rate of 2.22×10−1 K·s−1 after annealing at 1523 K for 7.2 ks. The alloy with the highest initial permeability exhibited the electrical resistivity of 0.732 μΩ·m and Vickers hardness of 210. The Ni-Fe-Nb-Ta alloys showed high permeability and low magnetostriction in a proper ordering state resulting from the effect of cooling.
The effects of vacuum pressure on the coercivity and magnetoresistivity of thin permalloy films during the deposition process were investigated. Samples of permalloy films ranging in thickness between 15 and 300 nm were deposited on a glass substrate by the electron beam method under a 10−4-10−6 Pa vacuum. The substrate temperature was 573 K, and the composition of the permalloy films was Ni-19 mass%Fe with near-zero magnetostriction. The average electrical resistivity (ρa) of permalloy films during deposition decreases, as vacuum pressure is decreased and film thickness is increased. However, since the change in magnetoresistivity (Δρ) is independent of vacuum pressure and film thickness, the magnetoresistivity ratio (Δρ⁄ρa) increases, as pressure is decreased and thickness is increased. On the other hand, the coercivity (Hc) and the magnetic anisotropy field (Hk) increase, as vacuum pressure is decreased. Moreover, the Hc and Hk peak at a thickness of nearly 70 nm. Through transmission electron microscopy, it is observed that the grain size in permalloy films increases as vacuum pressure is decreased. Auger analysis indicates that the concentration of oxygen in permalloy films decreases as vacuum pressure is decreased. These results suggest that the decrease in ρa and the increase in Hc under high vacuum are attributed to the decrease in oxygen and the grain growth in permalloy films.
The wettability of SiC against pure aluminium, Al-Si, Al-Mn, Al-Fe and Al-Cu alloys was measured by the method of SiC dipping into these molten metals. It became clear that in the wetting process of SiC against these metals, the alloying elements such as silicon, manganese and iron had good effect on the wettability by decreasing the incubation period, though copper gave almost no effect. The wetting process was able to be analysed by assuming that the rate of wetting was proportional to the nuclear number formed per nuit area and to the fraction of area of SiC unwetted by molten metal. The condensed zone of alloying elements for wetting was unable to be detected at the SiC-molten metal interface through EPMA measurements.
We have already reported the development of a new copper-carbon fiber composite which possesses the properties of copper, i.e., the excellent electrical and thermal conductivities and the property of carbon fiber, i.e., a small thermal expansion coefficient(1). The properties of the composite were expected to vary depending on the orientation of fibers. When applying the composite to some electronic devices, however, the properties of the composite have to be isotropic. For this purpose, several experiments were carried out on the composites with random orientation of short carbon fibers. Results obtained in this study were as follows: (1) The composite with random orientation of short carbon fibers swelled due to the elastic deformation of random-oriented carbon fiber’s skelton at temperatures above 573 K. It was deduced that in a three-dimensionally isotropic composite such as above-mentioned, the copper matrix softened above 573 K was fractured by the repulsive force of carbon fibers which had been elastically deformed and were released at heating, resulting in the swelling of the composite. This swelling occurred, when the fiber content was over 20 volume percent or the fiber length exceeded 0.5 mm. (2) It was found that the addition of carbide forming elements such as titanium was effective to prevent the above swelling.