On γ⇌α Transformation in Fe-Ni Alloys by Supercooling or Superheating

The characteristics of Fe-Ni alloy, it\u27s A_3-transfonhation and phase boundary between γ and α in the solid state, have been studied. It was concluded that, on cooling or heating with a marked hystersis, the lattice alone can be transformed without any change of concentration And such a lattice transformation was found to occur only at the time when the alloy was superheated or supercooled beyond the coexisting region of two phases. The equilibrium diagram of the alloy in the solid state was drawn from the temperature of lattice transformation

Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. IV : The Oxidation and Reduction Equilibrium of Magnetite with Gas Phases

It is known that magnetite crystals can contain excess oxygen over the stoichiometric composition of Fe_3O_4 by high temperature oxidation, and the oxygen content depends on the oxygen pressure in atmosphere and on the temperature. The Fe_3O_4 crystal has a crystal structure of the inversed-spinel type, in which O^ ions occupy the closed packed cubic lattice points, and the tetrahedral lattice sites (8 f) of its unit cell are occupied by 8 Fe^ ions, and octahedral lattice sites (16 c) by 8 Fe^ and 8 Fe^ ions statistically. When the magnetite crystal contains excess oxygen under an oxidizing atmosphere, it can be assumed that a vacant site accompanying two electron defects which result in two Fe^ ions is found on the octahedral lattice points occupied by Fe^ ions. Under these circumstances we can calculate the partition function of magnetite phase, from which the equilibrium relation between the oxygen content in magnetite, the partial pressure of oxygen in atmosphere and the temperature is deduced theoretically. These results are in good agreement with observations by Greig et al. and Darken and Gurry

Electrical and Magnetic Properties Related to Defect Structure in the Nonstoichiometric TiO and VO Phases

X-ray and neutron diffractions, electrical resistivity, magnetic susceptibility, Hall coefficient, and Knight shift were measured as a function of composition or temperature for the TiO and VO phases. We considered that the large amount of randomly distributed vacancies in these phases was not produced by thermal excitation but resulted from the internal energy gain which was ascribed to the formation of a metallic band due to the extreme contraction of lattice parameters. The maximum internal energy gains were calculated as about 1 eV for both phases. In a tentative model of the energy band structure for these phases, the Fermi energy was placed at the concave part in the density of states versus the energy curve, where the overlap of the bottom of the 3d-conduction band and the top of band owing to the 3d-electrons trapped at oxygen vacancies was strongly expected

Theory of Plasticity I : Correlation between Lattice Transformation and Plastic Gliding in Metals

Two fundamental relations, which are essential to express the resistance against the plastic gliding in terms of the thermodynamic function were derived, by considering the structure of dislocation. One is a relation which connects the free energy difference ΔG dissipated during the lattice transformation with the mechanical energy f・ΔL required for the plastic gliding and it has been assumed in the previous report. Here f is the resistance against the plastic gliding and ΔL the amount of deformation in the process of lattice transformation, its numerical value being 0.306. Another relation gives a method to obtain the free energy difference ΔG for a crystal in which the lattice transformation cannot take place under the usual condition

Theory of Plasticity II : Critical Shear Stress of Binary Alloys

The critical shear stresses of binary alloys were calculated by means of two relations which have been derived in the previous paper. The curves of critical shear stress protted against the concentration of binary alloys take various forms for different values of X and Y, where X=RT/H, Y=Φ_1/H and H=(F^i_a-F^r_a)-(F^i_b-F^r_b). F^i_a, F^r_a, F^i_b and F^r_b are the Helmholtz\u27s free energy of pure crystal composed of atoms A or B in the real or in the imaginary crystal phase respectively, Φ_1, being the so-called ordering energy of the alloy. The quantity H hardly depends on temperature at sufficiently high temperatures. As Y/X=Φ_1/RT becomes smaller, the critical stress curve protted against the concentration approaches to a symmetric form. But it is very unsymetric for small values of X and the central part of curve becomes flat for large Y. The comparison with observations reveals good agreement in the cases of Au-Ag, Cu-Ni and Cu-Zn alloys

Hall Effect in Liquid Copper Alloys

Hall coefficients of liquid copper alloys Cu-Bi, Cu-Sb, Cu-Sn and Cu-In have been measured by means of the double-alternating current method in a wide temperature range from 500° to 950℃. No temperature dependence of the Hall coefficient is observed in the liquid state of these alloys. The observed composition dependence of the Hall coefficient for the liquid Cu-Bi alloy is in good agreement with that calculated under the assumption of random mixing of Cu^ and Bi^ ions and of free electron approximation. In the other copper alloys, however, deviations from the free electron values R_0 calculated under the above simple situation are observed. It is considered that some of the constitutent atoms are randomly distributed and others are associated into clusters consisting of several atoms. Such a cluster is referred to as a pseudo-molecule. A theoretical formula for the Hall coefficients of these liquid alloys is derived as a function of the quantities n_R/N, 2p and αΩ_0 where n_R/N is the concentration of the pseudo-molecules, 2p is the number of localized electrons contributing to the bonding of the pseudo-molecule andαΩ_0 an effective volume of pseudo-molecule seen by conduction electrons. Using experimental values of these parameters obtained from the observation of the heat of mixing, magnetic susceptibility and the electrical resistivity, composition dependence of the Hall coefficients of the liquid Cu-In and Cu-Sn alloys are calculated in good agreement with the observed ones. The temperature dependence of the Hall coefficients estimated from the above formula is found too small to be observed with the present technique of experiment

Effect of Shot-Peening on fatigue Strength of Metals. II : Effects on Decarburized Steels

The effect of shot-peening on the fatigue strength of decarburized Si-Mn spring steels was examined by the rotary-bending and the reversed torsional method. The effect was very striking and it was observed that the endurance limit at 10^7 cycles of decarburized steels, which was reduced by about 50 per cent of limit of the polished specimen on account of the soft layer only about 0.05mm in thickness, increased by 40～50 per cent as the result of shot-peening of the decarburized layer. It might be possible to recover the strength in the non-decarburized state by increasing the peening intensity

Induction of mammotroph development by a combination of epidermal growth factor, insulin, and estradiol-17β in rat pituitary tumor GH3 cells

Several reports have indicated that prolactin-secreting cells (PRL cells) are generated from growth hormone-secreting cells (GH cells). We have shown that treatment with a combination of epidermal growth factor (EGF), insulin, and estradiol-17beta (E-2) induces the appearance of PRL cells in pituitary tumor GH3 cells. The aim of the present study was to clarify the involvement of mitosis in the cytogenesis of PRL cells in rat pituitary and GH3 cells. The effects of the treatment with EGF, insulin and E-2 on DNA-replication were studied by detecting the uptake of bromodeoxyuridine (BrdU) into the nucleus. In cultured rat pituitary cells, BrdU-labeled PRL cells were observed irrespective of the hormone treatment. In GH3 cells, BrdU-Iabeled GH cells and mammosomatotrophs (MS cells) were detected; BrdU-labeled PRL cells were not detected, however, when GH3 cells were treated with BrdU for 3 hr and then immediately examined for BrdU-labeling. BrdU-Iabeled PRL cells were found only when GH3 cells treated with BrdU were allowed to grow for another 3 days. This finding suggests that during the additional 3-day culture, BrdU-labeled PRL cells were generated from BrdU-Iabeled cells other than PRL cells. These results indicate that PRL cells are transdifferentiated from GH cells or VIS cells in GH3 cells by a combined treatment with EGF, insulin and E-2, while PRL cells in rat pituitaries are able to proliferate in response to the hormone treatment. Thus, there may be two pathways for cytogenesis of PRL cells the transdifferentiation of GH cells or VIS cells, and a self-duplication of PRL cells