Using old and new measurements, the change of the elastic modulus of copper, silver and gold with the addition of B-metals of the Zn and Cd period is analyzed. It is shown that the elastic modulus E in general decreases with alloying. An exception is the addition of Cd and Mg to gold, which increases the elastic modulus. The modulus change ΔE depends on two terms, one being proportional to the concentration c, while the other is proportional to the product of the concentration and the square of the valency difference between the alloying element and the base metal ΔZ. Thus an empirical relationship of the form
ΔE=−βc−αc(ΔZ)² (1)
is obtained. β and α are constants. The value of β only depends on the base metal and the period, being the same for all metals of one period. α increases with the distance of the period from the base metal in the periodic table. Experiments on poly-and single crystals give the same results.
This empirically determined relationship is compared with the theories of the elastic modulus of pure noble metals and its change caused by solid solution alloying. A good agreement is obtained, if the measured values are corrected to the lattice parameter of the pure metal. Due to this correction, a third term is introduced into equation (1). This term is proportional to the product c·ΔZ. Thus the expression for the corrected modulus change ΔC′_R is given by
ΔC′_R=(Kβ₂−β₁)c+Kα₂cΔZ−α₁c(ΔZ)² (2)
where K, β₂ and α₂ are constants.
The influence of the lattice parameter change (1⁄a) (da⁄dc) on ΔE is further analyzed. It is shown that like many other properties of the noble metals da⁄dc also varies systematically with ΔZ on addition of B-metals. In this case the formal relationship is given by
(1⁄a)(da⁄dc)=β₂+α₂ΔZ. (3)
Because β₂ may be positive or negative depending on the system studied, the lattice parameter may increase or decrease with alloying. Therefore, the change of the lattice parameter cannot be used for a unique explanation of the change of the elastic modulus due to alloying.
Finally the functional dependency of the change of various properties Δp of noble metals due to alloying with B-metals is discussed. It is shown that depending on the property in question, Δp may depend linearly or quadratically on ΔZ, or on a combination of both. These basic formulas may further be complicated by a term, which depends on the concentration alone, or on the product of the concentration and valency difference.

View full abstract

Interdiffusion in the aluminum-copper system was investigated in the temperature range of 400° to 535°C with diffusion couples of pure aluminum and copper metals.
In the aluminum-copper equilibrium phase diagram there are five intermediate phases in this temperature range, namely γ₂, δ, ζ₂, η₂ and θ. Electron probe micro line analysis of specimens studied indicated that all of these phases were located in the diffusion layer.
It appears that the layer growth of each phase is controlled by the process of volume diffusion since the rate of layer growth obeys the parabolic law. From the temperature dependency of the rate constants of layer growth, the activation energies of the individual phases were obtained.
The interdiffusion coefficient for each intermediate phase was calculated by the method introduced by Heumann, and the values obtained were consistent with those derived from Kidson’s equation for the δ, ζ₂ and η₂ phases.
Aluminum oxide powder was used for the measurement of the Kirkendall effect. It is clear from this measurement that diffusion in the multilayer system is controlled by the vacancy mechanism and that aluminum diffuses more rapidly than copper.

View full abstract

Masumoto et al. have previously discovered that alloys in composition near to Ni₃Mn exhibited a high permeability when developed to an optimum degree of order, and these alloys were named Nimalloy. In the subsequent work on the effect of various additives on the properties of Ni–Mn alloys, the highest initial permeability of 121000 and the highest maximum permeability of 643000 have been obtained with Ni–Mn–Fe–Cr–Mo alloys.
The results of Ta additions to Ni–Mn alloys show that with increasing Ta content, the permeability of Ni–Mn alloys at first increases gradually, goes through a maximum rapidly, and then decreases gradually. The highest initial permeability of 20470 is obtained on the alloy composed of 75.88% Ni, 19.47% Mn and 4.65% Ta when cooled at a rate of 240°C/hr from 900°C and baked at 440°C for 64 hr, and the highest maximum permeability of 84800 on the alloy of 75.37% Ni, 19.08% Mn and 5.55% Ta when cooled at a rate of 240°C/hr from 900°C and baked at 440°C for 65 hr. The latter alloy shows a coercive force of 0.0253 Oe and a magnetic hysteresis loss of 50.85 erg/cm³/cycle for the maximum magnetic induction of 5000 G, and its electrical resistivity being 52.7 μΩ-cm at 20°C.

View full abstract

Electron microscopic observation on the precipitation sequence in Cu–Be alloys was carried out. Clear images of G. P. zones on {100} planes, the ordered phase, the intermediate γ′-phase, the equilibrium γ-phase and then the informations about the size, shape and distribution in each stage were obtained more clearly than before. Strains associated with precipitates in the early stages of aging and some lattice defects such as dislocations, twins and stacking faults were observed, and these mean that the precipitation in Cu–Be alloys is associated with an exclusively large strain. These electron microscopic results were discussed as compared to those obtained by other methods.

View full abstract

Slip rotation during rolling due to slip on systems of the type {001}⟨110⟩ has been discussed on the standard (001) stereographic projection by the analysis based on the biaxial stress system. The crystal of (112) [\bar1\bar11] orientation in the intermediate rolling texture tends to rotate toward (011) [\bar2\bar11] by the operation of cross slip on cube planes. The direction of this orientation change is similar to that for the rotation by normal slip on two {111}⟨110⟩ systems with the highest resolved shear stress. Therefore, the (011) [\bar2\bar11] type rolling texture will be developed under the condition that a large amount of cube plane slip occurs at a high degree of deformation.
The formation of {011}⟨211⟩ type rolling texture in Al-3.5 wt% Al₂O₃ alloy (SAP) can be explained by the proposed theory.

View full abstract

The tempering process of high carbon martensite was investigated by means of the electrical resistivity measurement, dilatometry, and transmission electron microscopy. The first stage of tempering is not the precipitation of ε-carbide, but is probably the pre-precipitation stage such as the segregation of carbon atoms to the lattice defects or the carbon cluster formation. The second stage is the precipitation of ε-carbide which is related to the martensite by Jack’s orientation relationship. The retained austenite decomposed into lower bainite in the temperature range between 230° and 330°C. Tempering up to 330°C produced χ-carbide on the twin interfaces and this exhibited the monoclinic Pd₅B₂ type structure determined by Duggin. Further tempering up to 400°C, the in-situ transformation of χ-carbide into cementite occurred.

View full abstract

The structural change and some incidental properties of Al–Cr alloys (up to 3 wt% Cr) by rapid solidification at cooling rates between 10² and 10³°C/sec were investigated. The results obtained are as follows : (1) It is shown that the supersaturated solid solutions can be formed by rapid solidification and the minimum cooling rate to dissolve solute chromium supersaturatedly in pure aluminium is more than about 600°C/sec for 2 wt% Cr and about 1000°C/sec for 3 wt% Cr, respectively. (2) The microstructures of these solid solutions are composed of the dendrite cell structure of the primarily crystallized α phase and the appearance of CrAl₇, which has to crystallize primarily in an equilibrium condition, is obstructed. (3) The disintegration temperature of the supersaturated solid solutions of Al-2 wt% Cr alloys is 250°∼300°C. (4) Any precipitation hardening cannot be recognized by disintegration of these present metastable solid solutions.

View full abstract

Electrochemical measurements were carried out to clarify the mechanism of sulfur dewpoint corrosion of steels, i.e., the corrosion potentials of various kinds of steels in the mixtures of sulfuric acid-commercial active carbon powder, and sulfuric acid-boiler deposit. The effect of commercial active carbon and unburned carbon in boilers on the corrosion was discussed from these results.
Furthermore, the anodic polarization curves for steels in sulfuric acid at high temperature and concentrations were measured so as to investigate the relation between the anodic polarization characteristics and the resistance for sulfur dewpoint corrosion.
The experimental results are summarized as follows:
(1) In the mixtures of 65∼85% H₂SO₄ and active carbon at 110°C, the corrosion potentials of the resistant steels containing chromium or boron shifted exceedingly to the noble potential direction, while those of non-corrosion resistant steels such as mild and copper steels hardly changed during the test period.
It means that the corrosion resistant steels are easily passivated, and non-resistant steels are kept active. The commercial active carbon has the same influence on the dewpoint corrosion as unburned carbon in boiler deposits.
(2) The primary passive current densities of the anodic polarization curves in 80 and 85% H₂SO₄ at 110°C decreased with increasing chromium content in steels. The low primary passive current densities were corroelated well with the high resistivity of the steels for sulfur dewpoint corrosion.
(3) The mechanism of sulfur dewpoint corrosion of steels seems to be composed of the corrosion process of three steps. The first step is the corrosion of steels in sulfuric acid at relatively low temperatures and concentrations, the second step is in sulfuric acid at high temperatures and concentrations, and the third step is in boiler deposits containing both sufficient unburned carbon and sulfuric acid at the same temperatures and concentrations as in the second step.
The corrosion resistant steels containing chromium or boron are passivated at the third step, and their corrosion rates become extremely low.

View full abstract

Lattice parameter and length change were formulated as a function of irradiation dose on the hypothesis that an interstitial ceases to cause the lattice parameter change after interstitial clusters grow up to a certain size, whereas the interstitial still contributes to macroscopic volume change by one atomic volume.
The resultant formula was applied to the experimental results obtained by Kissinger et al. and Gray and Cummings on the lattice parameter and volume change in neutron irradiated Mo.
The hypothesis is found to be capable of explaining several features of the experimental results in a consistent manner. The nature of stage III defects in Mo was also discussed in conjunction with the experimental results.

View full abstract

In the current investigation, the difference in dissolution behaviour between metallic nickel and copper powders under the condition of ammonia pressure leaching has been studied. The leaching rates were determined at the NH₃ concentration of 1 or 1.5 mol/L and over the (NH₄)₂SO₄ concentration range from 0 to 1.5 mol/L, the temperature range from 15° to 200°C, the agitation range from 400 to 1200 rev/min and oxygen partial pressure range from 0.5 to 10 atmospheres. The solubility of nickel ammine sulphate in the H₂O–NH₃–(NH₄)₂SO₄ system was also measured in the present work. The experimental results obtained under these conditions are summarized as follows. The leaching of the nickel powder is shown to be a reaction of the zero-th order, indicating that the leaching time curve is a linear relation. But the leaching of the copper powder is an autocatalytic reaction, showing an extended S-shaped curve with a certain incubation period. The average leaching rate of the nickel powder is directly proportional to the oxygen partial pressure, and that of the copper powder to the square root of the oxygen partial pressure. The leaching amount of the nickel powder in solutions containing both ammonia and ammonium sulphate in the presence of oxygen is very small compared with that of the copper powder. This fact is independent of the difference in solubility between the Ni(NH₃)₆SO₄ and Cu(NH₃)₄SO₄·H₂O in the H₂O–NH₃–(NH₄)₂SO₄ systems.

View full abstract

In order to make clear the precipitation processes in Cu–Be alloy, the structural changes upon ageing of the 2 wt% Be alloy were examined in detail through an electron microscopy in particular by the use of the selected-area electron diffraction technique. The change in electron diffraction patterns with increasing ageing time or temperature was as follows. In the earliest stage, long streaks appeared in the ⟨001⟩ directions due to the formation of G. P. zones. Upon prolonged ageing, the streaks become shorter and intensity maxima appeared at about 2/3 of {002} reciprocal lattice vectors. This stage is distinct from the G. P. zone formation and may correspond to the formation of the γ″ phase. The structure of γ″ is considered to be a body-centered tetragonal, with Cu atoms at the corner and Be atoms at the body-center, and is different from that proposed by Geisler et al. Ageing at higher temperatures caused another superlattice reflection (CuAu(II) type, γ′) to appear and 2/3 reflections mentioned above to split. This splitting corresponded to the formation of the γ phase. From these observations, it has been concluded that the ageing sequence is α→G. P. zone→γ″→γ′→γ.
The structure of the final precipitate γ was identified to be the same as that of the equilibrium phase with the lattice constant 2.71Å. Then a new orientation relationship between the γ and α has been proposed, such that
{103}_γ⁄⁄{113}_α, ⟨010⟩_γ⁄⁄⟨1\bar10⟩_α.
Among several orientation relationships reported so far, only this one was consistent with our experimental results. In spite of the identity in structure, the final precipitates γ were associated with strain contrast around themselves, in contrast to the equilibrium phase. This fact suggests that the transformation γ′ to γ might be martensitic in the nucleation stage. The mechanism of γ′ to γ transformation is discussed along this line and from the viewpoint of coherency.

View full abstract

Effects of the stability of austenitic phases worked by shot-peening on the structures and chemical compositions of oxide films formed on 18–8 and 18–18 stainless steels by wet oxidation have been studied mainly by electron diffraction and characteristic X-ray micro-analysis.
The following results are obtained by the present investigation.
The oxide films formed on the surfaces of 18–8 stainless steels worked by shot-peening after mechanical or chemical polishing by oxidizing in high-temperature (300°C) water for 1 hr were the same in structure and chemical composition for both polished surfaces. The oxides were identical with the corundum type oxides consisting of (Cr, Fe)₂O₃ possibly accompanied by α-Fe₂O₃, showing characteristic X-rays of Fe and Cr.
On the contrary, the surface of the 18–18 stainless steel worked by shot-peening was covered with an oxide film which gave diffraction patterns showing clearly the existence of spinel type oxides with corundum type oxides of weak intensity under the same oxidizing conditions as in the case of 18–8 stainless steel. Further, besides Fe and Cr, Ni was detected from this oxide film. And the residual strain introduced by the shot-peening did not affect the structures and compositions of the wet oxidized films. From the above, it becomes clear that the stability of austenitic phases affects the structures of oxide films formed by wet oxidation of Fe–Cr–Ni austenitic stainless steels.

View full abstract