To study fracture initiation, mild steel plates, normalized or cold rolled, were notched and subjected to the tensile test at different temperatures. For the normalized specimens an abrupt or rapid change was observed in stress or COD to fracture at −130°C. A qualitative explanation was given to this transition phenomenon. The cold-rolled specimens fractured without general yielding in a ductile manner at all the testing temperatures; the fracture stress lowered with increasing strain rate, nearly independent of temperature.

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The mechanism of the negative magnetoresistance effect has hitherto been explained based upon the presence of the Weiss domain proposed by Berger et al. and Sudotov et al. The author discussed the effect from the measuring results of longitudinal and transverse magnetoresistance, dependence of the electrical resistivity on measuring current in zero and applied magnetic fields, hysteresis in longitudinal and transverse magnetic fields, and the magnetic field-rotation effect on the magnetoresistance. The measurements were carried out at 4.2°K for many kinds of high purity iron having the electrical resistivity ratio RRR=R (295°K)/R₀(4.2°K) ranging from 35 to 400. It is suggested from these measurements that the large negative magnetoresistance observed in the predominant low-field behavior is substantialy influenced by the domain configuration and domain wall displacement during the magnetization, and indirectly influenced by the varying impurity contents, because the impurity alters the domain configurations and prevents the domain motions. The maximum values of negative magnetoresistance of RRR=35∼400 iron specimens in the longitudinal and transverse fields are 7∼83% and 1∼75% respectively.

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In einer Al–Zn₂Mg Legierung mit 6.5 Gew.-% Zn und 1.2 Gew.-% Mg wurden die Ausscheidungsvorgänge, besonders die Größen- und Formänderung der ausgeschiedenen Teilchen und ihre Stabilität, sowie der Einflusse iner zweistufigen Auslagerung auf das Entmischungsverhalten mittels röntgenographischer Methoden und elektronenmikroskopischer Aufnahmen untersucht. In direkt abgeschreckten Proben wurden für die Bildung der G.P.-Zonen bzw. der metastabilen η′-Phase zwei Grenztemperaturen T_S und T_C festgestellt. Der Einfluß der zweistufigen Auslagerung kann als Folge der Keimwirkung der G.P.-Zonen oder des Wachstums von kleinen metastabilen η′-Teilchen erklärt werden. Um eine bessere Festigkeit durch Anlassen bei zwei Auslagerungstemperaturen (T₁<T₂) zu bekommen, kann die Behandlung bei T₁<T_S und T_C<T₂ empfohlen werden.

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The Cu-0.7% Cr alloy, the Cu-2.5% Be-0.3% Co alloy, and the Cu-4% Co₂Si alloy were used with the object of studying the critical cooling rate (CCR) for the solution treatment of an age hardening copper base alloy. The author introduced an idea of the critical cooling rate, defining it as the cooling rate necessary to obtain a supersaturated solid solution at room temperature. In this paper the critical cooling rate of each alloy was determined by Jominy end quenching methods using a specimen of 25 mm diameter and 100 mm length. The CCR obtained was 17°C/sec at 925°C for the Cu–Cr alloy, 60°C/sec at 500°C for the Cu–Be alloy, and 20°C/sec at 940°C for the Cu–Co₂Si alloy.

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In an age-hardening copper base alloy subjected to the solution treatment at a slow cooling rate, a supersaturated solid solution cannot be obtained at room temperature, and its age-hardenability deteriorates considerably. The critical cooling rate (CCR) in solution treatment was studied by the isothermal heat treatment methods.
The C curves which showed the precipitation behaviors of the alloying element in solution treatment were obtained in the Cu-0.7% Cr alloy, the Cu-2.5% Be-0.3% Co, and Cu-4% Co₂Si alloys. The CCR was determined to be 20°C/sec at 925°C (the nose temperature of the C curve) for the Cu–Cr alloy, 60°C/sec at 500°C for the Cu–Be alloy, and 20°C/sec at 940°C for the Cu–Co₂Si alloy. In the preceding paper the CCR of each alloy was determined by the Jominy test, i.e., continuous cooling, whereas in this paper the CCR was determined by the isothermal method, i.e., discontinuous cooling. There were good agreement in CCR determined by both methods.

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An investigation was made of the relation between microstructure and fracture characteristics of a low carbon tempered martensite. It was found in a previous paper that the cleavage crack traverses many martensite plates or laths in a linear fashion. On the analogy of the ferritic steel, the effective grain is defined as a region in which cleavage crack runs nearly straight. It is shown that the microstructure corresponding to the effective ferrite grain is the ‘co-variant packet’ extending throughout a bundle of the martensite. The reason why the structure consisting of fine martensites fractures with a large cleavage facet was found to be due to the fact that most of martensite plates or laths in a packet have the same crystallographic orientation and the cleavage plane {100}_α is quasi-continuous throughout the packet.

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The martensitic transformation in an ordered Fe₃Pt alloy has been studied by means of electron microscopy. The bcc martensite was found to have a superlattice which was expected to be formed by the Bain distortion from the Cu₃Au type superlattice of γ phase. A number of transformation twins on the {112} type (not of the {211} and {121} types) plane were observed in the martensite. The habit plane of martensite plates and the orientation relationship between the martensite and austenite were consistent with those in the disordered Fe–Pt alloy of the same composition.
The domain structures in the ordered γ phase were observed by using the dark field method, and it was clarified that the Ms temperature dropped rapidly according as the size of domains increased.

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Measurements of the Young’s modulus, rigidity modulus and thermal expansion in palladium-gold alloys were made at low and high temperatures after various heat-treatments and cold works. It has been found that the temperature coefficients of Young’s modulus and rigidity modulus in palladium-gold alloys annealed at 1000°C for 1 hr show a negative minimum value of −3.0×10⁻⁵ at 50% gold. However, the minimum turns to a positive value of +2.8×10⁻⁵ when further heated at 360°C for 15 hr after being subjected to water-quenching from 1000°C or 96% cold reduction. Also, the thermal expansion coefficient of palladium-gold alloys annealed at 1000°C for 1 hr has a minimum at 48% gold. This minimum corresponds to the maximum temperature coefficient of Young’s modulus or rigidity modulus in the palladium-gold alloys. Moreover, the hardness of these alloys heated at 360°C for 15 hr after water quenching or cold working is about two times that in the annealed state. These alloys are named “Pallagold” which is an abbreviation of palladium-gold alloy.

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The condition at the mold-ingot interface has a great influence on the cooling of ingots. But the influence appears not to be fully analyzed.
In this paper, it is shown that the cooling of ingots before solidification can be analyzed by considering the heat resistance R at the mold-ingot interface and approximate solutions are given by using the heat balance integral.
The results are as follows:
(1) For the semi-infinite mold and ingot, approximate solutions are obtained for a constant R, the linear variation of R with the interface temperature of ingot, and for the second-degree polynominal variation of R with the interface temperature.
(2) When the thickness of an ingot with constant R is 2a cm and the mold is semi-infinite, approximate solutions are also proposed.

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Seven iron-silicon alloys having various silicon contents up to about 14% were polarized in 2 N H₂SO₄. The relationship between silicon contents in the alloys and various properties such as the maximum or the limitting current density and the passive potential and the passive current density were investigated. 14% silicon alloy is much easier to passivate than iron, because the maxmum current density of the 14% alloy is equivalent to one-hundredth as large as that of iron and the passivation potential of the 14% alloy is close to its corrosion potential. An unusual variation in the passive current density with silicon content was observed; the passive current density increased with increasing Si content up to 6%, but decreased with increasing Si content above 6%.
The anodic polarization measurements were also carried out in 1 and 0.5 N H₂SO₄ with three iron specimens, 6 and 14% Si. The polarization behavior of the 6% alloy was only affeted by the sulphuric acid concentration. In 1 and 0.5 N H₂SO₄, the transition region from the active to passive state of the 6% alloy extended to the noble potential side accompanying a violent current oscillation. Such passivation phenomena can be explained to some extent on the basis of the silica formation on the anode surface.

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To make clear the origin of the Invar property, some physical properties of fcc (Fe_1−xCo_x)_0.89Cr_0.11 alloys which are most typical Invar alloys in the Fe–Co–Cr system (Stainless Invar) have been studied so far. In the present experiment, the temperature and composition dependences of thermal expansion for the alloys were measured and the following results were obtained:
It has been ascertained that these alloys have the same remarkable Invar characteristics as reported by Masumoto. Thermal expansions measurements at sufficiently high temperatures made it clear that the Invar property is caused by the effect of the spontaneous volume magnetostriction in the temperature range below the Curie point of short-range magnetic ordering. And the spontaneous volume magnetostriction at 0°K has been esitmated from the normal thermal expansion curves (only lattice vibration), compared with the thermal expansion of Ni. The value obtained on an alloy of x=0.6 was 12±1×10⁻³, about three times greater than that for Fe–Ni Invar alloys.
The microscopic mechanism or the cause of this large spontaneous volume magnetostriction may be ascribed to (1) the magnetic mechanism due to the characteristic electronic state of Invar alloys and (2) the elastic mechanism due to peculiar lattice properties of Invar alloys associateb with the α\ ightleftharpoonsγ martensitic transformation process which is common in each system having the Invar region.

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To make clear the mechanism of the appearance of large spontaneous volume magnetostriction of fcc(Fe_1−xCo_x)_0.89Cr_0.11 alloys, their magnetization and electrical resistivity were measured and the following results were obtained:
(1) The dependences of the mean magnetic moments and the Curie point on the concentration, x, and the outer electron concentration, n, of the alloys were similar to those in the Fe–Ni and Fe–Pd Invar alloy systems. That is, the alloys in these three systems are ferromagnetic on the Co- and Ni-rich sides and their ferromagnetic moments disappeared at the n of about 8.2∼8.4 which corresponds to the concentration containing Fe more than it in Invar alloys.
(2) The magnetization-temperature curve of the Invar alloys mentioned above did not follow Brillouin’s function.
(3) The electrical resistivity-temperature curves of the Invar alloys showed an anomalous broad maximum near the Curie point. And the residual resistivity were very large. These phenomenon may be explained by the co-exsistence of the ferromagnetic and antiferromagnetic states. It may be considered that the co-exsistence of the two magnetic states is closely connected with the sharp drop of the ferromagnetic moments near the concentration of Invar type alloys.

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