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Specimens of Henbury, Central Australia, and Canyon Diablo, Arizona, were fused and examined metallographically. Henbury gave a fine granular structure with probably nickel-rich grain boundaries. Canyon Diablo, containing schreibersite, gave a granular structure, except where the schreibersite produced a pearlite-like mixture. At the edges of this was a structure resembling martensite. Another specimen fused on charcoal was composed partly of grains of ferrite inclosed in cementite. The remainder showed a dendritic structure. This specimen exploded during fusion. Mention is made of other work in this field.

In the previous paper, authors have reported that the hydrogen diffusion phenomena in the steel were explanable comparatively well by Fick's law.The present experimental study was undertaken primarily to obtain an improved understanding of the behavior of hydrogen in various structures of steels.Discal specimens for the measurement of the hydrogen occlusion were prepared from a commercial steel S55C. The specimen diameter was 30 mm and its thickness was changed up to 16 mm, as indicated in the previous paper. The carbon content in the steel may affect the hydrogen occlusion. So the structures of the specimens, used in this experiment, were obtained by the heat treatment of the same kind of steel. Hydrogen was charged into the specimen by the cathodically charging method in 5% H2SO4 solution (current density; 0.2 Amp/cm2).Data which were obtained on the effect of the structures were studied using Fick's law, under the assumption that the materials were homogeneous on the average. The apparent diffusion coefficient, D, was computed from: D⋅t/L2=0.05 in which L represents the thickness of the specimens and t represents the period in which the hydrogen content of the specimen increases up to 1/2-maximum or equilibrium hydrogen content of the specimen from the start of the cathodic evolution.Solubility of hydrogen (i.e. equilibrium hydrogen content) in various structures was affected by the condition of the distribution of ferrite and cementite in the steel. The ferrite+pearlite structure showed a maximum solubility of hydrogen, on the other hand, the troostite structure showed a minumum. Moreover, the martensite structure showed the least.As to the diffusion coefficient of hydrogen, a maximum value was found in the ferrite+pearlite structure and a minumum one in the martensite structure.

In a previous paper on “The Inner Structure of the Pearlite Grain” read to the Iron and Steel Institute in 1922 the author advanced views on the stereometry of the pearlite grain. It was shown that the angle of inclination of a secant plane ω could be computed from the equation cos ω = Δ 0 /Δ ω , (1) where Δ 0 is the actual distance between two consecutive cementite or ferrite lamellæ and Δ ω is the trace of that distance on the secant plane. It follows from (1) that Δ ω = Δ 0 sec ω. (2) As the diameter d c of a cementite lamella or the diameter d f of a ferrite lamella is a constant fraction of Δ, it may be assumed that d ω = d 0 sec ω, (3) where d ω is the trace of d 0 on the secant plane.

Thermomagnetic measurements make it increasingly evident that the magnetic properties of steels are frequently those of mixtures of magnetic substances, each possessing characteristic properties, which contribute in a comparatively definite way to the properties of the material as a whole. In the case of a simple ferromagnetic substance, magnetising fields can generally be found in which the permeability variation with temperature is comparatively small except in the neighbourhood of the critical temperature. In such fields there is a very clearly marked peak in the permeability temperature curve for the substance. The explanation of this peak which the molecular theory affords is well known, and suggests that the phenomenon should be found common to all ferromagnetic substances. The immediate object of the present Paper is to show that it is exhibited by the carbide of iron (cementite) which exists in annealed carbon steels. For this purpose it is not necessary to isolate the carbide because, as shown in the Paper, the phenomenon is quite clearly discernible in the permeability temperature curves for the steel. The particular steel examined contained 0.85 per cent. of carbon. It was found that the fields necessary to evoke the comparatively sudden variations in the permeability of the carbide above described are small and such that the permeability variation of the iron present along with the carbide is slight in the neighbourhood of the critical temperature of the latter. The sudden gain and loss of permeability by the carbide as the temperature alters will be roughly equivalent to sudden removal and replacement of gaps in the magnetic circuit through the steel. They should therefore be attended by correspondingly sudden rise and fall of the apparent permeability of the material as a whole. This is found to be the case. There is a sharply marked peak near 210°C. upon the permeability temperature curve for the steel. In the absence of measurements between 200°C. and 220°C. the peak would escape notice and it is for this reason, probably, that it has not been recorded before. It could scarcely be found by accident. The search for it was prompted by the considerations outlined above in conjunction with results obtained in earlier work with Messrs. White and Barker.

The rate of dissolution of spheroidized Fe3C in ferrite in both high purity and commercial purity plain carbon eutectoid steels has been investigated. The experiments consisted of equilibrating wire specimens of spheroidized eutectoid steels at 650°C or 700°C and then jumping the temperature (in 2 to 7 m-sec) 4 to 32 C deg above the equilibration temperature. After heating, the specimens were maintained constant at the new temperature, and the dissolution of Fe3C was followed by observing the changes in electrical resistivity. The data are correlated to changes in the average carbon concentration in ferrite and are compared to the predictions of a generalized phenomenological model. Two important facts have been determined. First, the Fe3C ferrite interfaces are not in a state of local equilibrium during dissolution; the deviations from equilibrium in all cases were large. Second, the kinetics of dissolution are first order and the log of the reaction rate constants are a linear function of (1/T), whereT is the absolute temperature. These results lead to the conclusion that under the present experimental conditions, the dissolution of Fe3C in ferrite is controlled entirely by an interfacial reaction. A rather detailed description of the experimental procedure is included in this paper because the technique is new, and it is broadly applicable in the study of many metallurgical phenomena.

Investigations during the last few years have shown that a number of phases, especially borides, of the seventh and eighth group metals are isomorphous with cementite or crystallize in structures closely related to that of cementite. In this paper the recently obtained structural data are summarized and discussed. The influence of the radius ratio on trends in interatomic distances and lattice parameters is particularly considered. On basis of the presented data some general remarks on complicated'' interstitial phases are also made. (auth)

The present paper deals with the fine structure in a machined layer of the secondary phase grain such as that of cementite phase etc. And, the fine structure is discussed from metallugical point of view as a model of the secondary phase grain in an aluminium-silicon alloys. A particular attention is paid to the formation of fine structure in a machined layer according as the existence or not of a built up edge. Main results obtained are as follows:(1) The deformed primary crystal silicon of eutectic structure can be observed: Crashed and partly disappeared silicon, cracked one and that flowing in the direction of machining with the matrix, successively in the direction of depth from the skin of machined surface.(2) The transition zone of the fine structure of the primary crystal silicon in a cutting zone reaches the tool edge from the free face side of a boundary surface between the machined material and chips and occupies a vast zone of including the place where machined layer is to be positioned.(3) The transition zone of the fine structure with a built up edge occupies a vaster zone than that without the built up edge and along a built up edge nose the fine structure is formed from the skin of machined surface in the order as shown in (1).(4) The silicon and aluminium in eutectic structure excessively extends fibrously in the built up edge nose and a part of it constitutes the fibrous structure of machined layer.

The phase changes of steels in solid states may be classified into two kinds, the precipitation of ferrite (α) or cementite and the formation of martensite (α'). The mechanism of the one is very differ from other. The detailed interpretation has already been given by one of the present wriers. As regards the martensite, by the process of so called “ Umkloppen ” is generally accepted, although its n echanism has not yet been aufficiently interpreted. On this paper, we shall consider the mechanism in detail; to make the differencns of nature, clear between two kinds stated above. The facts hitherto obtained by the experiments on the formation of martensite show that this transformation consists of a great many minuites and impulsive change takis extremely short time. Hence it is concluded that the change occurs by the mechanism, does not need any diffusion of atoms as in the case of the precipitation. On the other hand, in view of the relation betwcen the crystallographic orientation of austenite (γ) and that of the martensite (α); the mechanism of the transformation should be like the mechanical slip in the case of twin-formation. Considering these facts, we support the theory that martensite forms through the process of Umklatypern. and proposes the following assumptions for its mechanism; so as to be possible to explain all the experimental facts. i) In the Umklrppen at first an atom which activation energy is lowered dues to the defect of the crystal lattice displaces to a new position which is a lattice point of the new phase (α'). And then. this displacement propagates in the crystallographic directions with such a great velocity of elastic vibration, which results a slipping of atomic planes to form one needle of martensite. ii) The elastic waves are accompanied by the formation of this martensite needle, other needles successively formed around it become a group. iii) Many of such a group form at random in the specimen.

This paper describes the components and composition of smut produced on iron and steel by pickling with sulfuric acid, which is the most popular agent for pickling.The experiments were conducted by X-ray diffractiometry and differential thermal analysis.The following results were obtained:1) The principal component of the smut produced by pickling with sulfuric acid was confirmed to be cementite Fe3C by X-ray diffractiometry and differential thermal analysis.2) The other components confirmed were sulfides and oxides of copper and nickel, oxides and phosphatides of iron, and sulfides of manganese. Accordingly, its composition was rather complicated.3) Compounds of cobalt and chromium were not confirmed. However, the presence of traces of these compounds would be probable.

The formation of pearlite from austenite has been studied in a eutcotoid carbon steel. The duplex nature of the eutectoid has been shown to be of great importance in determining orientation relationships in pearlite. It is shown in this paper that the atomic rows and planes in the ferrite, cementite and austenite are related by correspondence relationships of the type proposed by Sleeswyk. The orientation relationships between the ferrite and cementite are controlled by maintaining the plane of precipitation (i.e. of the austenite grain boundary) as a fixed or unrotated plane during the transformation. To define the orientation relationship fully, a direction which remains unrotated during the transformation is also required. This fixed direction is taken to be a direction which suffers the same distortion in the austenite-ferrite and austenite-cementite transformations and is thus a direction of zero-misfit between the ferrite and cementite. The predictions of this theory are in good agreement with experimentally observed orientation relationships between pearlitic ferrite and cementite. In particular, the analysis predicts not only the type A and type B relationships, but also the observed scatter about these specific orientations.

The X-ray elastic constants are found to be affected by many factors due to the selective nature of X-ray diffraction measurements. It is important to measure quantitatively the effect of these factors, not only to improve the accuracy of X-ray stress measurements, but also to elucidate the deformation mechanisms of polycrystalline aggregates.In a previous paper, an experimental and analytical investigation of the X-ray elastic constants was presented. The dependence of the constants on the diffracting plane as well as the change in these constants caused by uniaxial plastic deformation were observed experimentally and interpreted on the basis of crystal orientation, anisotropic elastic constants and deformation texture.In the present investigation, similar experimental techniques have been employed to determine the influence of carbon content (or cementite phase) and the effect of pre-working on the X-ray elastic constants of plain carbon steels. The results are reported for five compositions of hot-rolled plain carbon steel ranging in carbon content from 0.01 to 0.91%, and a forged 0.13% carbon steel. All the specimens were fully annealed and electropolished to remove the surface layer affected by machining.The following conclusions have been reached as the result of this investigation:(1) The absolute values of the X-ray elastic constants, S1 and S2/2, decrease with increasing carbon content, while the X-ray elastic modules, E, increases gradually. This phenomenon cannot be explained by the difference between the elastic constants of ferrite and cementite. It can be explained, however, by the constraint of deformation due to grain boundaries, since ferrite grains of the steels used in this investigation are smaller in size in proportion as the carbon content is larger. The smaller the grain size, the more prodominantly the deformation of the grain is influenced by the grain boundary and the deformation behavior approaches the Voigt's condition (uniform strain).(2) The absolute values of S1 and S2/2 of annealed hot-rolled steel decrease in the early stages of plastic deformation until they reach a nearly constant value at large strains.(3) In the case of the annealed forged steel, on the contrary, the plastic deformation causes the value to increase.(4) The absolute values of S1 and S2/2 of annealed forged steel are smaller at first than those of annealed hot-rolled steel of the same carbon content, but they approach the same constant level at high strain, as the plastic deformation causes change in the values. It is concluded that the X-ray elastic constants are affected according to the type of the pre-working employed before the annealing.(5) The values of the constants of the steels used depend upon the diffracting plane. In other words the absolute values of S1 and S2/2 measured on {211} by Cr-Kα radiation are considerably smaller than those measured on {310} by Co-Kα.

Cementite and iron percarbide are conveniently prepared by the methods described in the previous paper (part II). Iron percarbide has a narrow range of composition near 31 atomic % carbon and is identical with a carbide, assumed to be Fe 2 C, which was previously obtained by Hägg (1934). The iron percarbide unit cell is probably either orthorhombic, with dimensions a, 9.04(3); b = √3.a, 15.66(3); c, 7.92(1) kX, or hexagonal, with dimensions a' = 2a, 18.08(6); c' = c, 7.92(1) kX. There two possible units of structure are simply related, the volume of the latter being twice that of the former. The orthorhombic unit cell contains approximately 80 iron atoms, and the empirical formula for the carbide is Fe 20 C 9 . Although the existence of a carbide Fe 2 C is not disproved, it is unlikely that it has been prepared in this or any previous work. The cementite is identical with specimens formed below 700° C in steel and obtained by the action of carbon monoxide on ferric oxide. Both iron carbides are metastable. Iron percarbide decomposes giving cementite and carbon, and cementite breaks down less rapidly to give α iron and carbon.

RECENTLY, several papers have been published on the use of polarized light for revealing the grain structure of metals and alloys. Hone and Pearson1 showed that by examining under polarized light a polished aluminium surface which had been anodized in a suitable electrolyte, the grain structure was revealed, differently oriented grains appearing with different brightnesses. Woodward2, by etching ‘Monel’ metal in a specific reagent, has found similar effects. Polished surfaces of aluminium and ‘Monel’ metal, being optically isotropic, do not react to polarized light as do the optically anisotropic surfaces of tin, zinc, cadmium, etc., and the above authors1,2 have attributed the optical anisotropy of the anodized aluminium and etched ‘Monel’ metal to the anisotropic properties of the surface film formed during anodizing or etching. Although this explanation may be correct, there is a possible alternative which involves the surface contour of the specimen, for it is well known that if pearlite is examined under polarized light no reaction occurs unless the specimen is etched. This has been shown convincingly by Baeyertz3 to be due to the presence of fine parallel grooves on the surface, formed by etching away the ferrite and leaving the cementite lamellae in relief. Furthermore, Jones4 has shown that polarization effects can be produced by deeply etching a metal surface.