The solubility of nitrogen in liquid chrominum has been determined by a levitation melting technique 2220 to 2570 K. The observed solubility negatively deviates from Sieverts’ law at all temperatures investigated, and, above about 2370K, also shows a negative deviation from the high temperature extrapolation of the solubility-temperature relation obtained at 2220 to 2270 K. Correcting the observed solubility of nitrogen for the above deviations due to (i) thermal diffusion of a N2-Ar gas mixture, (ii) absorption of nitrogen by metal vapor, and (iii) dilution of nitrogen by metal vapor leads to (This article is not displayable. Please see full text pdf.) \
oindentwhich is larger than that in liquid iron or manganese and decreases with increasing temperature. Further, the pair interactions between Cr-N atoms and between N atoms in liquid Cr-N alloy have been discussed in terms of the oscillatory potential combined with a quasi-chemical model. Charge transfer is shown as such that Cr-and N-atoms are ionized to Cr+4.2 and N−1.2, respectively. These charge values are in accord with X-ray diffraction data and Pauling’s theory of atomic valency.
The aging structures of Al-Mg-Si alloys have been studied in detail by means of transmission electron microscopy, paying attention to the fact that cube-shaped precipitates are sometimes formed in this alloy system. The results indicate that the cube-shaped precipitates appear only in the (α+Mg2Si) two-phase alloys at aging temperatures and not in the (α+Mg2Si+Si) three-phase alloys, and the cube-shaped phases are metastable phases appearing at an intermediate stage between the rod-shaped and plate-shaped precipitates. The selected area diffraction has revealed that the phases are of the fcc structure with a lattice parameter of a=0.633±0.005 nm and have the relationship with the matrix. (This article is not displayable. Please see full text pdf.)
Anodic reaction of a PbO2(Pb) electrode in suspension-electrolysis of β-ZnS was studied by the interfacial impedance method. The experimental results obtained are as follows : (1) The double layer capacitance of the PbO2(Pb) electrode prepared is very high. The equivalent circuit at the interface consists of a frequency-dependent polarization resistance and the double layer capacitance in parallel. (2) On the anode of suspension-electrolysis, the graphite particles are oxidized electro-chemically to (C-O) or (C-OH) at the surface of PbO2(Pb) anode and the oxidation current increases with increasing suspension amount. (3) The PbO2(Pb) anode reaction in the electrolyte suspending only β-ZnS is the oxidation of H2S with the active oxygen generated by the discharge of water. In a low electrode potential region, the oxidation is controlled by both the charge-transfer process of the producing the active oxygen and the diffusion process of the product H+. In a high electrode potential region, the anode reactions are dominated by the first order chemical reaction process of the oxidation of H2S by the active oxygen and the diffusion process of the product H+. (4) In the case of the suspension system β-ZnS+graphite powder with the addition of Fe3+, the oxidation current is remarkably larger than the electrolyte without these substances. The reactions are mainly the oxidation of Fe2+ and the oxidation reaction of H2S, which is generated by the leaching of β-ZnS in acidic solution, with the subsequently produced Fe3+. The processes of the first order chemical reaction of the oxidation of H2S by Fe3+ and the diffusion of Fe2+ dominate the anode reaction.
The effects of quenching temperature on ordering in equiatomic CuPt alloy were investigated by means of electrical resistivity measurements during anisothermal annealing. The quenching temperature does not change three elementary processes of ordering, namely stage Ia(migration and annihilation of quenched-in excess monovacancies), stage Ib(annihilation of secondary defects) and stage II (migration of the thermal equilibrium vacancies). The higher the quenching temperature, the less the fractions of reaction in stage Ia. The decrease in stage Ia may be attributed to the concentration of quenched-in excess monovacancies. A divacancy in a locally ordered region has less mobility than a monovacancy.
Density of LiCl-NaCl-AlCl3 ternary melt has been measured over the composition range of less than 50 mol%AlCl3 and the temperature range of 800∼1200 K by means of the manometric method using a special electric furnace whose inside can be seen through. The results obtained are summarized as follows : The density of the ternary melt was expressed as a function of temperature and composition on the basis of the data measured. The density decreases with an increase in LiCl or AlCl3 content, and the degree of the decrease depends largely on the change in AlCl3 rather than LiCl content. The ternary melt of the composition range of less than 50 mol%AlCl3 was regarded as a reciprocal melt of (Li+,Na || Cl−,AlCl4−) because most of the aluminum chloride exists as AlCl4− anionic species in this composition range. The molar volume and the expansion coefficient of the reciprocal melt, and the partial molar volumes of the compounds LiC1, NaCl, LiAlCl4, NaAlCl4 were calculated. The molar volume increases with an increase in either the cationic fraction of Na+ or the anionic fraction of AlCl4−. The expansion coefficient depends on the anionic fraction rather than the cationic fraction. The partial molar volume of each compound slightly increases with the change of the cationic fraction, and decreases with the change of the anionic fraction. These results could be explained in terms of the size and the electrical charge density of ionic species and the hole volume of the compounds.
A study has been made on the formation and dissociation characteristics of hydrides in LaNi4Fe, LaNi2.5Fe2.5 and LaNi4Cr which are substituted for 20 or 50 at% of the Ni in LaNi5 by Fe or Cr. The results obtained are as follows : (1) The enthalpy changes ΔH for the dissociation of the hydrides in LaNi5, LaNi4Fe, LaNi2.5Fe2.5 and LaNi4Cr determined from the measurements of dissociation pressure-composition isotherms are −32.7, −34.5, −37.2 and −34.0 kJ/mol H2, respectively. (2) The substitutions of Fe and Cr which form the hydrides with lower values of ΔH than that in LaNi5 lead to lower plateau dissociation-pressures, although the Fe and Cr substitutions lead to a shorter plateau corresponding to the concentration of storaged hydrogen. (3) LaNi4FeH3.5, LaNi2.5Fe2.5H1.6 and LaNi4CrH1.8 are formed at 0.1 MPa (1 atm) of dissociation hydrogen corresponding to atmospheric pressure at 25°C, and the application of these metal hydrides as hydrogen storage media is discussed. (4) The evolution process of hydrogen dissociated from the hydride of LaNi4Cr, with the formation of holes through an Au thin-film evaporated onto the surface of a hydrided sample, was observed in vacuum on a scanning electron microscope.
An assessment has been made of the effect of subzero-treatments on the mechanical properties of Al matrix composites reinforced with 1∼3 stainless steel fibers (Vf6.2∼15.7%) fabricated by casting in vacuum. Four kinds of stainless steel fibers which had different Ms points were used as reinforcement. Pullout, tensile, creep and hardness tests were carried out before and after the subzero-treatments. Metallographic examinations were also carried out. The results indicate that the tensile and creep strength in some specimens in which fiber transformation occurred by the subzero-treatments show a higher value than that expected by the so-called rule of mixture. This may be attributable to the defect-free interface produced by the hydrostatic compressive stress as a result of martensitic trans-formation in fibers. The stress estimated from elasticity and plasticity is large enough to produce such an effect.
The solubility of ferrite forming elements, Be, Ti, Mo, P and Sb, in αFe at temperatures between 600 and 1200°C was determined by X-ray diffraction and microprobe analysis. It was confirmed that the solubility decreased abnormally in the ferro-magnetic region, especially in the case where the alloying element had a pronounced tendency to lower the Curie temperature. Thermodynamic analysis was made on these data, separating the free energy of αFe-X solid solution into their magnetic and non-magnetic components, and approximating the former by a modification of the magnetic free energy of pure αFe, as proposed by Zener and Hillert et al. It was cansidered that the more abruptly the solute atoms lower the Curie temperature the more pronounce the tendency to destroy the magnetic spin ordering and receive an additional repulsive force from the neighboring Fe atoms. This seems to account for the extraordinarily low solubility.
The solubility of Be, P, Mo and W in αFe in the Fe-X-Co ternary system was determined by X-ray diffraction and microprobe analysis. It was detected that the anomaly in solubility of these elements due to the magnetic transition was enlarged with the addition of Co. This result agrees well with an anticipation from the fact that the ferromagnetic character of αFe is generally emphasized by alloying of Co. Using an improved method of Zener and Hillert et al., these solubility data were analyzed thermodynamically by separating the free energy of αFe phase into the magnetic and non-magnetic components. The metastable miscibility gap in αFe-Mo-Co system was also estimated, and it was concluded that the miscibility gap in the αFe-Mo binary system expanded with the addition of Co.
Substructures developed during the steady-state creep of Fe-4.1 at%Mo bcc solid solution at 1100∼1200 K under 6∼40 MPa have been observed by transmission electron microscopy. The stress exponent, n, of the steady-state creep rates is 3.2±0.2. This result means that this alloy shows Class I behavior under the present creep condition. Sub-boundaries consisting of dislocation networks as well as rather homogeneously-distributed dislocations within subgrains are always observed. This fact suggests that the presence or the absence of sub-boundaries does not necessarily indicate the importance of viscous gliding of dislocations during steady-state creep deformation of solid solution alloys. Dislocation density within subgrains, ρG, and total dislocation density, ρT, increase with increase in the applied stress, σa : ρG∝σ1.5a and ρT∝σ1.3a. The length of sub-boundaries per unit area, L, which is reciprocally proportional to the subgrain diameter, increases with σa:L∝σ0.5a. The mean spacing of dislocations within sub-boundaries, l, decreases with σa:l∝σ−0.6a. The average internal stresses, ‾σi obtained by stress-transient dip-tests using a back-extrapolation technique are roughly proportional to \sqrtρG, \sqrtρT, and 1⁄l.
The apparent viscosity of fusible alloys suspended with copper powder was determined to be larger when the suspending solid particles were finer in size and complex in shape like that of the dendrite. On the basis of these results, the growth features of primary crystals in various cast irons were studied by means of measuring the apparent viscosity in the early stages of solidification. The results are summarized as follows. In the case of hypoeutectic cast irons : (1) When the iron is held in the liquid state, the primary dendrite becomes finer with increasing holding time. (2) Inoculation facilitates the primary crystallisation and the formation of fine dendrites with many arm branchings. In the iron held for, 30 min after inoculation, however, coarser dendrites than those in the original iron are found. (3) In the process of holding the iron at a fixed temperature during solidification, dendrite arms are enlarged or extinguished violently and thus the coarsening of the whole dendrite grains proceeds gradually. This phenomenon is different from the coarsening process of the dendrite in hypoeutectic Al-Si alloys. In the case of hypereutectic cast irons : (4) No change in size of the primary flake graphite is found in irons held in the liquid state. (5) Inoculation to the hypereutectic cast iron facilitates the crystallisation of primary flake graphites and changes their shape.
The fact that samples prepared by a high frequency induction melting and centrifugal casting method is excellent in uniformity suggests that this method is adequate for the preparation of tool and high speed steel samples containing a large amount of carbide-forming elements for instrumental analysis. In this study remelted samples which were prepared from tool (JSS 600∼605) and high speed (JSS 606∼611) steels for chemical analysis by this method were analyzed in comparison with the same standared samples for instrumental analysis. The method for the assessment of the remelted samples was as follows. The equations of the working curves were derived from the data for the standard samples for instrumental analysis by curve fitting with orthogonal polynominals. The F-test was performed for comparison of the mean squares of both data. Emission spectral analysis (Cu, Ni, Cr, Mo, V, W) and X-ray fluorescence analysis (Ni, Cr, Mo, V, W) of tool steels showed that some of the standard samples gave abnormally higher values in tungusten analysis. The working curves successfully constructed from the standard samples when excluded those samples with abnormal tungsten content and included Fe-W alloy samples (JSS FXS 375∼378). In order to make clear the cause of this higher analytical value, the microstructures were investigated with an optical microscope and an electron probe X-ray microanalyzer. It was inferred as a main cause that comparatively large tungusten carbide scattered non-uniformly in one standard sample, while there was no carbide in the remelted samples. In X-ray fluorescence analysis (Co, Cr, V, Mo, W) of high speed steels, there was a discrepancy in analytical values of vanadium between the standard sample and the remelted one with a high vanadium content (V: 3.19%), and the analytical values of tungsten in the high tungsten standard samples showed considerable scattering in positive errors. Microstructure observations confirmed that the positive errors were due to the presence of coarse unmelted carbide in the standard samples.