The present work was carried out so as to determine the phase diagram on the aluminium rich side in the Al–Mg system with 0.5 wt% silver by means of the micrographic method, electrical resistivity measurements and differential thermal analysis.
The solubility of magnesium in aluminium was decreased by the addition of 0.5 wt% silver since the solid solubility curve of the α phase in this alloy shifted to an appreciably higher temperature range than that in the binary Al–Mg alloy. The results obtained by electron probe microanalysis and electron diffraction analysis showed that the equilibrium precipitates in the alloys with 0.5 wt% silver (≤9wt% Mg) consisted mainly of a ternary compound, the T phase (Mg₃₂(Al, Ag)₄₉), at higher temperature (≥300°C). On the other hand, in an Al-9 wt% Mg-0.5 wt% Ag alloy aged at 300°C, the β phase was detected and the precipitation of the β phase became more dominant as the aging temperature lowered. The ageing behaviour of an Al-6 wt% Mg-0.5 wt% Ag alloy was also studied by hardness measurements and electron microscopic observations. The precipitates in the alloy containing silver were finer and more uniformly distributed than those in a binary Al-6 wt% Mg alloy, which accounts for the remarkable increase in its age-hardening. The improvement of the age-hardening by a small addition of silver might be partly associated with the direct effect of the increased degree of supersaturation for precipitation of the T phase. However, as the most important cause for the improved age-hardening, it is considered that the increased supersaturation and the chemical affinity between silver and magnesium would bring about the formation of the stable G–P zones, which act as the sites of nucleation of T phase precipitation.

View full abstract

The austenite and martensite phases of Fe-9.70% Al-1.46% C steel have been observed by means of transmission electron microscopy and electron diffraction. It was verified that the austenite γ phase has a superlattice of the Cu₃Au type, and the assumption in a previous paper (Trans. JIM, 11(1970), 152) that the martensite lattice would be formed by the Bain distortion from the Cu₃Au type ordered γ lattice was confirmed unambiguously. Besides, it was found that the ordered γ phase consists of anti-phase domains of about 120 Å size. From the appearance of cross streaks around the fundamental spots as well as superlattice spots in the ⟨100⟩ directions, the anti-phase domain boundaries were identified to be of the second type.

View full abstract

Kinetic behaviors of ordered Fe–Co and βCuZn alloys have been investigated with basic equations derived on the basis of the Bragg and Williams theory which is extended to a binary alloy of the bcc structure containing vacancies. It is then assumed that atom movements occur in two mechanisms, a direct interchange of atoms and an interchange through vacancies. The order dependence of vacancy concentration is also considered following the method of Girifalco. Both the two mechanisms assumed here for the interchange of atoms play an important role in the ordering process. The interchange through vacancies is dominant particularly in the ordering process for ordered βCuZn alloy. The numerical calculations have been carried out by using the appropriate values estimated from the data on diffusion and other experiments. In ordered Fe–Co alloys the order parameter at room temperature is retained up to about 500°C. Beyond 500°C it begins to vary rapidly with the maximum rate at about 550°C and finally reaches its equilibrium value. This result is in agreement with the interpretation by Yokoyama, Takezawa and Higashida. On the other hand, the temperature dependence of the order parameter in ordered βCuZn alloy exhibits a negligible anomaly near room temperature.

View full abstract

Since the original discovery of Masumoto et al. that Ni–Mn alloys containing about 24% Mn or less show high permeability when subjected to a proper heat treatment, much work has been carried out so as to investigate the effects of additions of various elements on the special characters of the high-permeability alloys in the Ni–Mn system named “Nimalloy”. The series of experiments have achieved good results in producing a number of excellent magnetic alloys. It has become clear that Ni–Mn–Fe alloys should be cooled as rapid as possible and Ni–Mn–Mo alloys as slow as possible to develop their excellent magnetic properties. As in the case of Ni–Mn–Fe–Cr alloys, it was expected that Ni–Mn–Fe–Mo alloys would exhibit excellent mgnetic properties when treated at an intermediate cooling rate. A detailed investigation has confirmed that excellent magnetic alloys in the quarternary system can be produced by a moderate cooling rate at the level of furnace cooling. The highest initial permeability of 46540 has been obtained on the alloy composed of 76.88% Ni, 11.22% Mn, 4.67% Fe and 7.23% Mo which was cooled from 900°C at a rate of 400°C/hr, and the highest maximum permeability of 270000 on the alloy of 77.13% Ni, 10.66% Mn, 5.15% Fe and 7.06% Mo which was cooled from 900°C at 2800°C/hr. The latter alloy has a coercive force of 0.0019 Oe and a magnetic hysteresis loss of 0.53 erg/cm³/cycle, its electrical resistivity being 89.4 μ Ω-cm (20°C).

View full abstract

The activities of non-metallic component in metal-nonmetal binary melts were measured by the TIE method.
In the moment the electrolyte touches with the both electrodes simultaneously, the concentration cell is constituted as follows:
Bi–S|PbCl₂+PbS|Bi–S(sat. Bi₂S₃).
The experimental results measured in the temperature range 520° to 620°C showed that at concentrations smaller than 0.065 mole fraction of sulfur the activity curves of sulfur indicate a positive deviation from ideality but is negative at larger concentrations; the negative deviation becomes larger as the temperature increases.
It was also found that the solubilities measured of bismuth trisulfide in molten bismuth agree well with those in the literature.

View full abstract

The low-temperature deformation behaviour of nickel containing up to 4 volume per cent zirconia is investigated by employing tensile tests and differential-stress creep experiments. At a given strain, the activation area decreases with increasing volume fraction of the dispersoid. The data on flow stress are not in quantitative agreement with the Orowan model for initial yielding and the Fisher-Hart-Pry mechanism for strain hardening. It is thought that the increase in flow stress and work hardening rate for the alloys may arise from the high initial dislocation density and its rapid increase with strain. The rate-controlling mechanism for deformation of zirconia-dispersed nickel appears to be the thermally activated intersection of dislocations.

View full abstract

The e.m.f. measurements were carried out in the temperature range of 1100°∼1250°C by means of the following galvanic cells employing solid electrolytes:
Ni, NiO/ZrO₂(+CaO)/O(in Cu or Cu alloys).
From these experimental results, it was found that (1) in the Cu–O system, Henry’s law was obeyed from the low oxygen content of 100 ppm to such a high content as to precipitate Cu₂O, and the activity coefficient of oxygen (the reference state for oxygen is pure gas at 1 atm) was 0.120 at 1100°C, 0.150 at 1150°C and 0.195 at 1200°C, (2) the activity of oxygen in liquid copper was decreased by the addition of tin and nickel and depressions became more pronounced by the addition of nickel than that of tin, and (3) the interaction parameters ε₀^(Sn) and ε₀^(Ni) were determined as
ε₀^(Sn)=−6.45×10⁴⁄T+41.57 and
ε₀^(Ni)=−7.93×10⁴⁄T+46.47, respectively.

View full abstract

Measurements of thermal expansion and Young’s modulus at −150°∼500°C have been carried out with single crystal specimen, 3 mm in diameter and 12 cm long, of 18–12 type stainless steel. At the same time the rigidity modulus of a polycrystal specimen was measured at room temperature. At 20°C the Young’s moduli determined are 10.34×10⁵, 21.00×10⁵ and 32.00×10⁵ kg/cm² in the ⟨100⟩, ⟨110⟩ and ⟨111⟩ directions, respectively, while the rigidity moduli are 14.13×10⁵, 5.92×10⁵ and 6.70×10⁵ kg/cm² in the three principal directions, respectively. In both cases, the elastic anisotropies are very large. The Young’s moduli in the three principal directions decrease monotonously with temperature. The mean temperature coefficients of Young’s modulus at 0°∼40°C in the three principal directions are e_⟨100⟩=−51.70×10⁻⁵, e_⟨110⟩=−37.80×10⁻⁵ and e_⟨111⟩=−24.90×10⁻⁵, respectively.

View full abstract

Various properties of cast irons are finally determined by oxygen, sulfur and trace elements contained in them. Effects of oxygen, sulfur and trace elements on the graphitizing tendency of cast irons were shown quantitatively on the structural diagram. The law of oxygen and sulfur concerning the graphitizing tendency of cast iron was shown on the structural diagram. The contents of oxygen and sulfur to give the best quality to gray cast iron are 20∼30 ppm and 150∼300 ppm respectively. The mass effect of gray cast iron can be quantitatively shown by ∂K⁄∂φ. It was shown from the structural diagram that trace elements affect the graphitizing tendency of gray cast iron. As methods to express the quality of cast iron, σ_B²⁄K²−HB and K·HB−σ_B were proposed utilizing the K value.

View full abstract

The mechanism of loss of coherency of θ′ plates in an Al-4% Cu alloy has been studied by a high voltage transmission electron microscopy using a tiltable specimen heating stage. The θ′ plates lose coherency by the nucleation of misfit dislocations at the periphery of the plates. Burgers vectors of the misfit dislocations are identified by a contrast experiment as an a⟨100⟩ type lying on the flat faces of θ′. Irradiation of high voltage electrons promotes the formation of misfit dislocations at relatively low temperatures. Loss of coherency of θ′ occurs also in the unirradiated area at high temperatures.

View full abstract

The diffusivities of Au and Cu in pure Al were determined by the residual-activity method with radioactive tracers, ¹⁹⁸Au and ⁶⁴Cu, in the temperature range between 290° and 650°C and between 375° and 620°C respectively.
The dependence of the diffusion coefficients of Au and Cu on temperature are given by the following equations:
D_Au/Al=(2.2_−0.7^+1.0)exp{(−32000±1000)⁄RT}cm²⁄sec.
and
D_Cu/Al=1.3exp(−33000⁄RT)cm²⁄sec.
The pre-exponential factor and activation energy for diffusion of Au in Al are very similar to those for diffusion of Al, Cu, Ag, and Zn in Al, and it is suggested that the volume diffusion of Au in Al occurs by the vacancy mechanism.
Although Au has extremely low solid solubility in Al, the characteristics of the diffusion of Au in Al were substantially different from those of other elements, in particular the transition metal elements, which are only slightly soluble in Al.

View full abstract

The potentiostatic experiment with the following electrochemical cell was carried out until the steady current was confirmed, and the change of current was measured in the temperature range of 980°∼1130°C:
Air, O(in liquid silver)/ZrO₂(+CaO)/Air.
On the basis of the experimental results, the values of log (I-I_steady) were plotted against time and the relation was shown to be nearly linear after several tens of minutes. From the slope of the linear relation, the diffusivity of oxygen in liquid silver was determined at four different temperatures.
The diffusivity can be expressed by the following equation, which is in good agreement with previous reliable data.
(Remark: Graphics omitted.)
Under this experimental condition, it was found that this analytical method was better than the other methods based on the change of electric current on the short time side or on the value of steady current.

View full abstract