Cu–Zr–Cr alloy does not soften by prolonged high-temperature heating and its electrical conductivity ranges between 75 and 80% IACS, so that the alloy is extensively used as electrodes for diverse welding purposes.
A study of the origin of high softening temperature in this alloy has been made using a transmission electron microscope. The results show that the presence of Cr and Zr atoms in copper solid solution retard the recovery, recrystallization and precipitation. The recovery and recrystallization, which result from the dislocation climb and glide, may be retarded by : (1) the apparent locking of dislocations due to the presence of Cr or Zr atoms or both, and (2) the reduction in self-diffusivity of the Cu in copper solid solution due to the presence of Cr or Zr, or both. From the retardation of recovery and recrystallization in the ternary alloy, it can also be predicted that the diffusion coefficient of Cr or Zr, or both, is low.
Aging at 400°C for 1 hr after roll-flattening hardens the Cu–Zr–Cr alloy. However, transmission electron microscopy does not reveal the origin of the hardening. This may correspond to the phenomena known as “low temperature anneal hardening”.

View full abstract

To know the initiation of stress corrosion cracks, the temperature dependence of internal friction near 0°C was measured on 18–8 austenite stainless steel specimens which were water pooled after a stress corrosion treatment in boiling 42 wt% MgCl₂ aqueous solution under 80% tensile stress of yield strength. At 0°C there was a maximum peak of internal friction in the specimen.
The main experimental results are as follows:
(1) There is a linear and parallel relation between the 0°C peak height of internal friction and (Q_w⁻¹−Q_r⁻¹), where Q_w⁻¹ and Q_r⁻¹ are the internal friction at room temperature of the specimens with and without pooled water respectively. The parallel relation does not exist when stress corrosion cracks initiate.
(2) tan⁻¹{(the increase of 0°C peak height)/(the increase of (Q_w⁻¹−Q_r⁻¹) corresponding to the increase of 0°C peak height)} is almost constant when stress corrosion cracks do not initiate, but it increases remarkably upon initiation of stress corrosion cracks.

View full abstract

The oxide layer thickness was obtained from the change in the amount of reflection light on the surface of copper oxidized in air during isothermal heating. A maximum and a minimum were observed in the amount of reflection light on the copper surface oxidized during isothermal heating at 200°C.
The thickness of the oxide layer was calculated from equations obtained by Macsman using the optical constants of Cu₂O. The thickness thus obtained was in good agreement with that by weight measurements.

View full abstract

Measurements of the longitudinal magnetostriction of the [100] rod single crystals of iron containing 0.5% Al have been carried out at ordinary temperatures, in the thermally demagnetized state and the alternating-current demagnetized state, respectively, using the optical lever method. It has been found that the dependence of the magnetostrictive behaviors of these specimens on the method of demagnetization is greater than that of the [100] single crystals of pure iron reported until now. Also, it has been determined quantitatively, from the magnetostriction vs. magnetization curves in the thermally demagnetized state, that the volume fraction of domains with magnetization vectors along the direction of easy magnetization nearest to the rod axis in the unmagnetized state ranges from 0.11 to 0.15, and that the value of the magnetostrictive constant, λ₁₀₀, is 15.7×10⁻⁶. Furthermore, the deviation of the domain distribution in the state of remanent magnetization from that governed by Kaya’s rule has been evaluated.

View full abstract

The longitudinal magnetostriction of the [110] rod single crystals of iron containing 0.5% Al has been studied at ordinary temperatures, in the thermally demagnetized state and in the alternating-current demagnetized state, using the optical lever method. It has been found that the magnetostrictive behaviors of these specimens depend markedly on the method of demagnetization, and, from the magnetostriction vs. magnetization curves in the thermally demagnetized state, the volume fraction of domains with magnetization vectors along the direction of easy magnetization nearest to the rod axis in the unmagnetized state ranges from 0.19 to 0.23; furthermore, the deviation of the domain distribution in the state of remanent magnetization from that governed by Kaya’s rule has been evaluated. Moreover, the fact that the magnetostriction vs. magnetic field curves in the magnetization range of rotation are linear, irrespective of the method of demagnetization, can be explained by the experimental results that the square of the magnetization is approximately proportional to the magnetic field, but to the magnetostriction as well. From the above considerations, an attempt has been made for the determination of the magnetostrictive constant, λ₁₁₁.

View full abstract

The longitudinal magnetostriction of the [111] rod single crystals of iron containing 0.5% Al has been studied at ordinary temperatures, in the thermally demagnetized state and in the alternating-current demagnetized state, using the optical lever method. It has been found that the dependence of magnetostrictive behaviors of these specimens on the method of demagnetization is not so conspicuous as in the [100] and [110] specimens, although it is affected distinctly in the magnetization range of wall displacements. From the magnetostriction vs. magnetization curves in the thermally demagnetized state, the deviation of the domain distribution in the state of remanent magnetization from that governed by Kaya’s rule has been evaluated. Furthermore, it has been noted that, as for the difference of magnetostriction between the state of remanent magnetization and that of magnetic saturation, the relation deduced from Kaya’s rule holds practically, unlike the [100] and [110] specimens. Moreover, the fact that the magnetostriction vs. magnetic field curves in the magnetization range of rotation are linear, irrespective of the method of demagnetization, can be explained in a way similar to that of the [110] specimen.

View full abstract

The activation energy of recrystallization of a 3.48% Ni–Fe alloy annealed isothermally over the temperature range 425°∼500°C was obtained from the changes in Vickers hardness. The activation energy thus determined was 69600 cal/mol.

View full abstract

The effect of annealing on stress-strain curves of an Al-3% Li alloy which had been overaged and then cold-rolled was studied, by comparing with the changes in lattice constant and electrical resistivity and also in the transmission electron micrographs. A sharp yield drop followed by the propagation of Lüders bands was observed when the Al-3% Li alloy was annealed in a recovery range, i.e. 200°∼380°C. The same type of yielding was also observed an Al-4.7% Cu alloy. The Al-3% Li alloy, annealed at 320°C, was deformed at various temperatures (−196°∼230°C) with various strain rates (7.4×10⁻³∼3.7×10⁻⁶sec⁻¹). At low temperatures, the specimen deformed with Lüders bands which were followed by work-hardening. In the tensile test, at room temperature with a low strain rate or at 100°C, the specimen necked and tore off in a Lüders band and showed “pseudo-brittleness”. The specimens, which showed the propagation of Lüders bands, was in a fully recovered or partially recrystallized condition. The average grain diameter was 0.9∼1.9 μ. The measurements of lattice constant and electrical resistivity revealed that partial decomposition of a dispersed second phase, i.e. AlLi, took place, when the specimen was annealed at a temperature above 220°C. This temperature was much lower than the over-aging temperature, i.e. 360°C. It was found that the decomposition of the second phase was closely related to the presence of a sharp yielding. The above results were discussed in terms of general requirements for the yielding. It was concluded that the decomposition of the precipitates, AlLi, was not always necessary for the occurrence of the sharp yielding but promoted the pinning of dislocation sources near the boundaries.

View full abstract

The diffusion phenomena between cemented carbides and machined steels, and the cratering wear formed on the carbide tools during cutting of steels were investigated in relation to the carbon contents in both materials.
The results obtained were as follows: (1) Three sorts of diffusion layers were generally observed, but low carbon WC–Co alloy/low carbon steel combinations resulted in appearance of a fourth layer consisting of M₆C-type compound due to decarburization of the alloys. The formation of this compoud was markedly checked in WC–TaC–Co and WC–TiC–Co alloys, owing to the effect of tantalum carbide or the β (WC–TiC solid solution) phase acting as a source of carbon. (2) An abnormal increase of wear was observed only in the combination of low carbon WC–Co alloy tools/low carbon steels (or 18–8 stainless steel), due to the formation of that compound just below the cratered surface. In WC–TaC–Co and WC–TiC–Co alloy tools, this abnormal wear was naturally diminished. (3) Resistance to cratering of low carbon WC–TiC–Co alloy tools was superior to that of high carbon tools at a high cutting speed, because of the better mechanical properties at elevated temperatures (as expected from the binder phase composition). (4) It was concluded that the carbon content should be increased in cemented carbides at a low cutting speed, but it should be reduced in WC–TaC–Co or WC–TiC–Co alloys at a high cutting speed. Low carbon WC–TiC–Co alloy tools with particular structure were proved to be very useful for cutting stainless steels.

View full abstract

The effects of mean particle size and carbon content (or binder phase composition) on transverse-rupture strength of WC-10% Co two-phase alloys were investigated, by using specimens having the strength approx. 20∼50% higher than that of the specimens which have been reported by many other researchers. The test on transverse-rupture strength was conducted in accordance with ASTM–B 406–64. Even in such alloys of high strength, it was confirmed that the strength depended on the carbon content. The strength of the alloys reached its maximum at a mean particle size of about 2.2 μ. The maximum value was about 350 or 370 kg/mm² in the high or low carbon alloy, respectively. Some considerations were given to the mechanism of the dependence of strength on the carbon content.

View full abstract

The ordered alloy Ni₂Cr has been investigated by means of electron diffraction, electron microscopy, calorimetry, resistometry and tensile tests. The formation of the Pt₂Mo type superstructure is revealed by an electron diffraction study on the single crystalline specimens. The size of ordered domains is of the order of magnitude of several hundred Å even in the well annealed state. The so-called ‘K-state’ which is characterized by the initial increase in electrical resistivity upon isothermal annealing is attributed to the existence of very fine ordered domains. Superdislocations consisting of triple dislocations are sometimes observed in various stages of ordering, and the mechanical properties are briefly discussed in the light of electron microscopic observation. The energy and entropy of transformation are evaluated as about 1.0 kcal/g·atom and 1.2 cal/g·atom-deg on the alloy of 32.1 at% Cr annealed at 500°C for about 3000 hr.

View full abstract

In a copper-25, 19 at% aluminium martensite a lamellar mixture has been found by transmission electron microscopy. The stacking sequences of the close-packed structures involved are ABCBCACAB and AB.

View full abstract