Both experimental and theoretical investigations have been undertaken on the order-disorder transformation in Fe-Al alloys with less than 50 atomic percent Al. In the neighborhood of 25 percent Al these alloys are known to exhibit a two-step transformation, namely from DO3 to B2 and from B2 to disorder. The phase diagram and the Al occupation probabilities for each lattice site are coordinated by a statistical theory, and the most reasonable phase diagram for the interpretation of X-ray diffraction data by powder specimens has been obtained. This diagram is compared with the one obtained experimentally by our measurement of electrical resistivity and specific heat of the alloys. A possibility of coexistence of two phases with different types of order is also discussed.
The π phase of Mn-Al and Mn-Al-Ti alloys, wich appears in the process of the isothermal transformation of the quenched ε phase to the stable phases (i.e. ζ and β-Mn), has been experimentally investigated and the T.T.T. diagrams of the alloys with various compositions have been determined. Details of the isothermal transformation were found to depend on the alloy compositions as shown below: (This article is not displayable. Please see full text pdf.) \
oindentThus, an alloy consisting of the π phase alone can be obtained by the isothermal transformation (I) when the Mn-content is less than 56 at% in Mn-Al alloys or 55 at% in Mn-Al-2.7 at%Ti alloys. In alloys with more than 3.5 at%Ti, the ferromagnetic phase is π′ (bcc, a=3.14 Å).
The magnetic intensity of the π phase Mn-Al alloys of various compositions, with or without additional elements such as Ti, Cr, Fe, Co, Ni and Cu, has been measured. The decrease in Mn content and the addition of Ti element have been found to increase the magnetic intensity. The results of Mn-Al binary alloys can be explained in terms of the magnetic structure suggested by P. B. Braun, while those of the alloys with the additional elements can be explained by the magnetic structure with a modification (i.e. the alloy elements at the lattice positions which are estimated from the atomic volume as well as the electronegativity) and the empirical rule for magnetic moments of ferromagnetic binary alloys.
An anomalous oxide band structure was observed parallel to the surface in the internally oxidized layer of nickel alloys with silicon up to 4 wt%. The morphology of the oxide bands was as follows. (1) The distance between oxide bands in the internally oxidized layer increased with decreasing concentration of the solute and with increasing distance from the surface of the specimen. An ordinary formation of oxide particles was observed between these bands. (2) The diffusion of oxygen through the internally oxidized layer seems to be interrupted by these oxide bands. Therefore, the rate of internal oxidation was decreased by the formation of oxide bands. (3) The formation of oxide bands seems to be attributable to the diffusiblity of solute atom in the matrix to the oxide particles which are simultaneously nucleated at the equal distance from the surface. An oxide band was formed from a bundle of very small rod-shaped oxide crystals parallel to the direction of internal oxidation.
Following the preceding work, the siliconized couples were also used in the present experiment. Along the diffusion direction micro-Vickers indentations were arranged at a small interval and then the couples were heated at temperatures from 1150° to 1200°C. A position, on which the indentation showed the maximum movement after diffusion heating, was regarded as the interface (so-called marker interface) according to Heumann’s theory. Independent of the diffusion time and temperature the silicon content in the interface was nearly constant. The interface movement is proportional to the square root of the diffusion time. This relation is given by the equation (This article is not displayable. Please see full text pdf.) From the velocity of the interface movement and the chemical diffusion coefficient obtained here, the partial diffusion coefficients can be calculated by means of the Darken relations. DFe and DSi are represented by the following equations: (This article is not displayable. Please see full text pdf.) \
oindentIt is confirmed that DSi is about two times larger than DSi.
Drawability of metal sheets is known to be determined mainly by the factors such as preferred orientation and grain size. These factors affect differently to various metal sheets. In mild steel sheets the preferred orientation is the dominant factor for improvement of drawability and texture control provides the posibilities of improving drawing performance. On the other hand, in 18-8 stainless steel and 70-30 brass sheets the drawability is rather insensitive to the crystallographic texture and the useful improvement in drawing performance is accomplished by the control of grain size. In nickel-silver sheets the contribution of these factors is not clear. The authors have studied the drawability of nickel-silver sheets in terms of the preferred orientation and grain size, and obtained the following results: (1) With increase in reduction of cold rolling, the component orientated in (225)[73\bar4] develops in the annealing texture and the r-value in the direction 45° apart from the rolling direction becomes high. But conical cup value does not vary correspondingly with the r-value, so the drawability of nickel-silver sheets is insensitive to the crystallographic texture. (2) The drawability of nickel-silver sheets is well correlated to the grain size, and the coarse grain sheet is favourable for drawing performance.
Elgiloy was studied by means of tensile strength, spring limit, hardness and thermal expansion cofficient measurement, X-ray diffraction, and optical and transmission electron microscope observations. The mechanism of age hardening in Elgiloy was not explained by optical microscopic observation, thermal expansion cofficient measurement and X-ray diffraction. By transmission electron microscopy and electron diffraction it was found that Elgiloy subjected to rolling and annealing, precipitated fine α-Co particles and suggested that the precipitation causes hardening and an increase of the spring limit.
This is a part of systematic studies on the influence of grain boundary on the hardness and structure changes in rolling aluminum bi-crystals. In this report, changes in hardness are reported. Square bars of bi-crystals, made from 99.999% pure aluminum ingots by Bridgman’s method, were rolled successively at room temperature to 95%. After each rolling, changes in hardness were investigated. Main experimental results obtained were as follows: (1) Recrystallization (perfect softning) occurs in a crystal grain of which both the direction normal to the rolling plane and the rolling direction lies near 〈111〉, but softning did not occur in a crystal grain of which the direction normal to the rolling plane and the rolling direction are near 〈100〉 or 〈110〉. (2) Recrystallization occurred far from the grain boundary. (3) For consideration of the recrystallization of bi-crystals, “Orientations of crystals before plastic working” should be considered in addition to conventional factors.
For the purpose of clarifying the influence of grain boundaries on the hardness and structure, a investigation was performed on changes in hardness as reported previously. In the present study, changes in structure were investigated. Bi-crystals were prepared from 99.999% pure aluminum ingots by Bridgman’s method. The bi-crystals were rolled by 95% at room temperature. Main experimental results obtained were as follows: (1) Recrystallization occurs in a crystal grain of which both the direction normal to the rolling plane and the rolling direction lies near 〈111〉, but no recrystallization is observed in a crystal grain of which the both direction normal to the rolling plane and the rolling direction lies near 〈100〉 or 〈110〉. These phenomena were observed by means of micro-structure studies and Laue X-ray photography. (2) The shape of the bi-crystal boundary was not changed after rolling of high working degree. (3) Deformation bands were observed in a crystal of which the vertical direction of the rolling plane and the rolling direction is near 〈111〉.
Hardness measurements were carried out to study the recrystallization behavior around 700°C of these alloys, which were cold rolled after annealing for 2 hr at 910°C. The time required for recrystallization of No. 1 (Fe-1.90 wt%V-0.007 wt%C-0.0048 wt%N) alloy is longer than that of No. 2 (Fe-0.97 wt%V-0.98 wt%Cr-0.006 wt%C-0.0030 wt%N) alloy and No. 3 (Fe-2.00 wt%V-0.006 wt%C-0.0034 wt%N) alloy. These alloys quenched from 910°C show the age-hardening at 700°C which seems to be due to the precipitation of fine carbides or nitrides. Especially the increase in hardness of No. 1 alloy is large. It seems likely that these precipitates have significant effects on the recrystallization behavior of these alloys. The marked retardation of recrystallization of No. 1 alloy seems to be interpreted by these precipitates.
Properties of various WC-NbC-10%Co alloys (vacuum-sintered at 1375°C for 1 hr) were examined in relation to their niobium carbide and carbon contents, comparing with the properties of WC-TaC-10%Co, WC-TiC-10%Co alloys, etc. previously reported. Main results obtained were as follows: (1) Niobium carbide hardly dissolved in the binder phase at room temperature, in the same way as tantalum carbide or titanium carbide in cemented carbides. (2) The niobium carbide phase contained about 18%WC at room temperature, which was about three times larger than in the tantalum carbide phase. (3) The composition of the binder phase and the carbon content of the niobium carbide phase varied regularly with a slight change in carbon content of the alloys. This resulted in the regular changes in various properties of the alloys, as has been observed in alloys containing tantalum carbide or titanium carbide. (4) The (WC+NbC+γ) three-phase region of the alloy was extended with increasing niobium carbide content. The amount of the extension was intermediate between those of WC-TaC-Co and WC-TiC-Co alloys. (5) The phase boundary between the (WC+NbC+γ) three-phase and (NbC+γ) two-phase regions was found at the content of about 75%NbC in the alloys (about 83% in carbides); that is, the boundary located at the higher WC content than that of tantalum carbide containing alloys. The niobium carbide content on the boundary, as in the case of tantalum carbide containing alloys, slightly increased with increasing carbon content. (6) The hardness of the alloys was superior to that of WC-TaC-Co alloys, but the transverse-rupture strength was lower. (7) The effect of niobium carbide content on the properties was confirmed to be intermediate between those of tantalum and titanium carbide contents.
The thermal dilatation- and electrical resistance-temperature curves have been measured for an Al-Ni-Co-Ti magnet alloy aged at various temperatures. The both curves show analogous changes except a portion and two different transformation mechanisms in the aging process of the alloy, as in the case of Alnico 5 in the previous report. The results obtained are summarized as follows: (1) Changes are observed at two points under 600°C in the specimens aged below 650°C. Both changes may be the transformation to a metastable state, like the order-disorder transition, but the one of them was not observed in Alnico 5. (2) After aging above 700°C, a kink point appears at about 450°C on the electrical resistance-temperature curves. This corresponds to the Curie point of a precipitates, but disappears after re-aging at 550°C. (3) All curves obtained show a large curvature at about 650°C. This means that the change of a stage before the precipitation comes to an end. (4) A curvature is observed in the temperatures between 700° and 800°C, after aging below 700°C. This change disappears after aging at 800°C and corresponds to the progress in precipitation. (5) A large curvature is observed at about 850°C. This may correspond to the solution of precipitates.
In the welded steel structures, the welded joint frequently plays a decisive part in the occurrence of failure owing to: (a) the residual stress, (b) the metallurgical changes, and (c) various types of defects caused and produced by welding. Therefore, in this study, to obtain fundamental information about the fracturing behaviour of welds, various V notch Charpy specimens were sectioned from the multirun mild steel weld metal by taking the welded structures into consideration, where the columnar (dendritic) and the refined grain structures produced by the heat affect at the time of welding existed alternatively. On these specimens, the impact test was carried out by recording the relation between load and time during impact and the fracturing behaviour of weld metal was analyzed. As a result of this study, the notable tendency observed is that the impact values decrease when the structure at the root of the notch is dendritic and the growing direction of the columnar (dendritic) structure coincides with the direction of crack propagation. However, when the crack advances transversely against the growing direction of the columnar structure, the impact values were not reduced, although the structure at the root of the notch is dendritic. The results mentioned above are explained partly by Petch’s equation on the relation between grain size and transition temperature and partly by the difference in the probability of crack propagation through the grain boundary.
The effect of the additional elements (Sn, P) and sliding speed on the wear mechanisms of phosphor bronze were investigated. A continuous measuring apparatus of electrical contact resistance between wear surfaces was designed. By applying this apparatus with other measuring methods of wear properties, it followed that there were various processes in wear of phosphor bronze—abrasive (metallic surface in appearance), oxidized, lubricated by molten eutectic, and adhesive by softening of materials—which changed systematically against the factors such as additional elements and sliding speeds, etc., and that the continuous measuring apparatus of electrical contact resistance between wear surfaces clearly recorded the changes of wear mechanisms indicating its usefulness for a study of behaviours of wear products on contact surfaces. From the results of the present study, a schematic diagram of wear mechanisms of phosphor bronze against three factors—contents of Sn and P, and sliding speed—was proposed.
A static study has been made on the process of dissolution of copper into liquid tin under static and isothermal conditions. The results obtained from the experiments made at 14 different temperatures ranging from 340° to 750°C are summarized as follows: (1) Because of the large solubility limit of the system, dissolution velocities are very large: About two minutes after dipping, solute concentrations of the liquid at definite temperatures attain 90% of solubility limits for these temperatures. (2) In such systems having large solubility limits as in the case of the Cu-Sn system, rate constants of dissolution can be calculated by Eqs. (14) and (12). (3) At temperatures between 340° and 427°C, the rate constant of dissolution increases with increasing temperature, but it decreases almost monotonously with increasing temperature from 450° to 540°C except that it shows a small maximum at about 518°C. This particular trend may be explained by the facts that the phases contacted with the liquid metal are η for the lower and ε for the higher temperature range. Further, the fact that the solution rate constants measured are 5∼20×10−3 mm/sec and are larger than in other systems measured under static conditions, is attributed to large natural convections produced by large density differences in the present system. (4) At 340°∼427°C, 518° and 586°C, the rate of dissolution is determined by diffusion of Cu atoms in the effective boundary layer of liquid metal near the solid surface. In the range 450°∼540°C, however, the rate is determined by the surface reactions of Cu atoms jumped into the liquid. (5) Owing to the natural convections caused by the density differences, the dissolution velocity of the upper part of the specimen is larger than that of the lower part.
Aluminium cast alloy belongs to the same system as wrought aluminium, but the former is superior to the latter in strength and castability by the effects of larger amounts of additional elements. Accordingly, it may be essential to discuss the mechanical properties, especially, the machinability of aluminium cast alloy from the point of view apart from wrought aluminium due to their rough structure and segregation or crystal precipitation peculiar to their cast structure. In this paper, as the first step of study on the cutting mechanism of aluminium cast alloy, the orthogonal cutting of lautal alloy is experimented to discuss the form, properties and behaviours of the built-up edge and to obtain the influence of the built-up edge on the cutting surface and the cutting resistance. As the results, the built-up edge decreases with the rise in tool rake angle and is slightly observable at 50°∼60° of the rake angle. The edge angle of the built-up edge is nearly equal regardless of tool rake angle, and the apparent rake angle is about 46°. In this experiment, the built-up edge may be looked upon as a quasi-stable state because most of the built-up edges adhere stably on the tool rake, a part of which locally grows, breaks up and falls down at its tip. So, in the case of various tool rake angles, the cutting resistances are nearly equal to each other because of the same apparent rake angles, and when the local break-up of the built-up edge is dominart, the cutting resistance fluctuates greatly and deteriorates the cutting surface.
The isothermal diagrams of the 12%Cr-Fe-C-N system were examined at various temperatures between 1300° and 700°C in the range of compositions up to 0.4% carbon and 0.3% nitrogen. In consideration of the phase relationship, the phase reaction of the 12%Cr-Fe-C-N system was made clear and the sectional diagrams were constructed at fixed contents of 0.1 and 0.2% carbon and 0.1 and 0.2% nitrogen. In the Fe-Cr-C-N system, it was assumed that a quaternary peritecto-eutectoid reaction (γ+Cr23C6\
ightleftarrowsα+Cr7C3+Cr2N) exists at about 780°C which can be represented by the isothermal hexahedron of a five-phase region consisting of α, γ, Cr23C6, Cr7C3 and Cr2N. The carbide Cr7C3 detected in the present work was expressed by a formula of (Fe2Cr5)C2.4N0.6.
The magnetic shunt properties of one kind of M.S.O. Alloy (31%Ni, 8.5%Cr and res. Fe) containing C from 0.019 to 0.150% were studied. The magnetization curves at 0° to 40°C were measured by the ballistic method. The dimension of specimen was 0.4 cm in diameter, 3.1 cm in length, and so the demagnetization factor N was 0.30. The experimental results on magnetic shunt properties are summarised as follows: (1) With increasing C addition, the permeability decreases at first and then increases slightly through a feeble minimum. It is assumed that the former decreasing is due to the impurity of C and the latter increasing due to the formation of Fe6Cr17C6 which is speculated by the microscopic texture and the calculation. (2) The temperature coefficient of permeability becomes larger with increasing C addition, and its linearity becomes worse.