This paper presents the results obtained on measuring the change of dimension of various nitriding steels by nitriding. After nitriding a steel, containing 0.41 % C, 2.62 % Cr, 0.42 % Mo and 0.28 % V quenched in oil from 950° and tempered at 700°, at 500° for 50 hrs, it has been found that the percentage of dilatation of diameter and length decreased with increasing diameter. The tempering temperature, varied from 500° to 700°C, has no influence on the percentage of dilatation. The percentage of dilatation varies with steel composition and it increases with the elevation of nitriding temperature.

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Notwithstanding their security in vacuum, some specimens of cast copper, as is generally known, change their attributes in hydrogen atomosphere by heating, due to the so-called “Hydrogen-Shortness”: i.e., when these specimens are heated in hydrogen atomosphere, the broadening of each grain boundary- can been observed to take place, together with the formation of conspicuous cracks at this boundary. To study the phenomena above stated, the present writers examined the differential dilatation of each specimen during the procedure of heating. As the consequence of this examination, the abnormal dilatation of the specimens was found to occur about 650° the more remarkably, the more the amount of copper oxide contained in these specimens was increased. Especially, it was noticed that such a dilatation could never be detected, with deoxidated specimen free from copper oxide. Thus, this abnormal dilatation, which may be intimately associated with the aforesaid “Hydrogen-Shortness”, is conceived to be due to the reduction of copper oxide by hydrogen. But'the reaction between copper oxide and free hydrogen molecule expressed by
Cu₂O+H₂→2Cu+H₂O takes place about 400° instead of 650°. Moreover, it should never give rise to the augmentation of the volume of specimens, as was observed in the present examination. Accordingly, we may legitimately conclude that the hydrogen atoms once dissolved in copper, are responsible for the reduction of copper oxide and the advance of the

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Ausarbeitung des Systems im Bereich von 0 bis 30% Magnesium and 0 bis 30% Mangan mit Hilfe von thermischen and mikroskopisehen Untersuchungen. Nach den Untersuchungen ergebnissen sind die darauffolgenden nonvarianten Punkte festgestellt.
L_??_α+Al₆Mn 659° L+Al₄Mn_??_Al₆Mn 710° L+Al₃Mn_??_Al₄Mn 840° L_??_α+β448°
L=Al₄Mn_??_α+Al₆Mn 605° L=α+Al₆Mn+β440°

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Der Einiiuss des Zusatzes von Mangan auf die Al-Cu-Mg-Legierungen wurde systematisch untersucht. Die Hauptversuchsergebnisse sind wie folgt : (1) Es wird festgestellt, dap etwa 1.5 % Mangan in AI-Cu-Mg-Legierungen löslich Bind, . Höhere Maugangehalte fuhren zur Bildung von Al₅Mn. (2) Die Löslichkeit von Al₅Cu₂Mg₂(S) ina-Mischkristallen wird durch Manganzusatz nicht verhindert. (3) Darch Zusatz von Mangan wird die Rekristallisationstemperatur der kalteewalzten Al-Cu-Me-Leeieruneen erhöht.

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It is well known that in internally strained metals, for example, in cold, worked metals, the potential barrier which an atom must surmount to become mobile is very much lowered. The mutual diffusion of metals, therefore, must also become very rapid in such a strained metal. Dr. Matano was perhaps the first who had investigated this phenomenon quantitatively and systematically. His investigation, however, contains two defects : (1) he did not define the degree of plastic deformation, and (2) he used an alloy (Cu-Sn about 5 atomic%) which was in the concentration range where diffusion constants could not be considered as independent of concentration at low temperatures, say below 550°. This is due to the fact that the activation energy of this alloy decreases markedly towards high concentrations. The present author, taking care of these points, has carried out strict experiments. The alloy used is Cu-Al containing 15•7 atomic % of Al. On its surface pure. copper is electro-plated. In-the case of this alloy diffusion constants can be considered to be roughly independent of concentra-tion, especially at low temperatures, and the low temperature range is of importance, as we shall see later, for this investigation. Two kinds of base alloys are used : the one completely annealed, and the other cold-worked (elongated about 50 %). The method of experiments is almost the same as that of Dr. Matano, , There diffusion constants are decided from lattice constants which are proportional to alloy concentrations. The measurement of lattice constants, however, have been carried out more strictly using pure metallic silver as a standard sub-stance. The lattice constant of standard silver was, of cource, strictly measured previously. The results are tabulated in Table 2, and are illustrated in Fig, 2.
We can see from these results that the effect of internal strain disappears in the temperature range higher than a certain definite temperature (in this case about 770°). This is accounted for by the abrupt recrystallization, which changes the strained sample into annealed one instantaneously. The activation energy in the case of annealed alloy is 42, 900 cal/mol, which coincide completely with the value of Rhines and Mehl. And the activa-tion energy in the case of cold-worked alloy is 24, 600 cal/mol. These results will furnish some key points to elucidate the phenomenon of so-called “Platzwechselvorgang”.

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The cause of high strength in extruded aluminium alloy have been attributed to the stability of recrystallization structure formed under working. The present author has carefully examined the cast structure of S D and found its speciality owing to the existence of Mn in the alloy. Other elements, having the same effect as Mn, have been reserched, and it is recognized that the extruded materials with those elements also show high strength. The stability of recrystallization structure, which is the cause of high strength in the extruded material, results from this special structure existing.

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An increasing demand of making use of sub-zero temperatures in the scientific as well as in the industrial field has brought an growing activity to the study of the properties of metals and alloys at low temperatures, especially, of their mechanical properties. Here is described the construction of a cryostat-box whose wall is made of carbonized cork boards. The interior of this box can be cooled, by the aid of liquid nitrogen, down to -130°, and preserve it with the accuracy, a few tenth -of one degree. In this cryostatat-box is placed a portable type tensometer, i.e. a small size testing machine, the construction and the manipulation of which are also explained here.

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