γ→a transformation of the pure iron is supercooled in various degrees by cooling velocity, but it can not be suppressed to room temperature. The lattice transformation in Fe-Ni alloys can be occured only at the time when they were supercooled or superheated beyond the coexisting range of two phases and it is not affected by cooling or heating velocity, depending only upon the concentration. These are essential difference from the case of the allotropic transformation in iron. The phase change in equilibrium state is determined from the free energy (volume energy) of the system, but in not equilibrium state or supercooled state it must be noticed that the surface energy due to formation of a nucleus of the new phase can be never neglected to the volume energy. From such a point of view, supercooling phenomenon described above have been investigated theoretically.

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Es ist von grosser Wichtigkeit, das Abschreckungsdiagramm in Bezug auf die Längenveränderungen des stahis bei Temperatureinwirkung, also bei Erwärmung beziehungsweise Abkühlung, zu untersuchen. Denn daraus zieht man die Folge, um die Zustandsveränderung theoretisch zu erklären, praktisch, den Eindringsgrad der Abschreckung zu messen, um damit die Qualität des Abschreckungsmittels u. s. w. bcurteilen zu können. Wenn die Abschreckungsdiagramme auf dem Mittelpunkt und der Umkreiszone einen Unterschied aufzeigen, dann kann man die Wärmespannung errechnen, und das Umwandlungsverfahren nach der inneren Zone hin wird ermessen.
In diesen Untersuchungen wurden die Temperatur- and Längenveränderungen mittels des elektrischen Verfahrens ermittelt, durch Verstärker verstärkt und auf der Braunschen Röhre als Abschreckungsdiagramm veranschaulicht. Auf diese Weise konnte der Einfluss der Umwandlungswärme, die bis jetzt ausser Acht gelassen wurde, sehr klar beobachtet werden.
Zum Schluss wird noch ein neues Verfahren gezeigt, welches für die Bestimmung der Beziehungen zwischen. Längenveränderung und Temperatur am Mittelpunkt sowie an der Umkreiszone besonders geeignet ist.

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Some phenomena concerning the hydrogen absorbed in a high speed steel are shown as follows: (1) Hydrogen % in the high speed steel ingot is chiefly dependent on the humidity in the air. So the mean rolling yield in a certain month is nearly controlled by the mean humidity in the same month. (2) Hydrogen % in the 150kg high speed steel ingot ranges from about 0.0002 to 0.0001. As compared to the hydrogen in a plain C steel ingot (0.0006-0.0007%), hydrogen in the high speed steel ingot is much less. (3) The special aging phenomenon due to the hydrogen diffusion in a steel at room temperature is observed in a high speed steel. Specimens held at room temperature for a month show the higher impact values than the fresh ones.
To verify quantitatively these phenomena due to the hydrogen diffusion, the diffusion experiments are tried at various temperatures, using the Fick's diffusion equation. Diffusion constant can be estimated from the following formula:
_??_
where a, b and c stand respectively for length, width and height of a block specimen and q₁, q₂ for respectively the evolved hydrogen per unit time at the time of t₁ and t₂. From the results at 800°, it is cleared that the diffusion constants of hydrogen lower gradually in the following order: high C tool steel (No. 4 in Table 3), JES H. S. steel 2nd class (No. 1), JES H. S. steel 3rd class (No. 2) and Mo H. S. steel (No. 3). At room temperature, however, the diffusion constants lower gradually in the following order: plain C steel (No. 5 in Table 3), Mo high speed steel (No. 3), JES H. S. steel 2nd class (No. 1) and JES H. S. steel 3rd class (No. 2). Here it is noted that the total amount of absorbed hydrogen in Mo high speed steel is evidently largest.

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The diffusion phenomena between silver and copper were microscopically examined on the Cu-specimens and Ag-specimens which were respectively electroplated with silver and copper. The results obtained are as follows: (l) Copper mainly diffuses into silver. (2) At a temperature below the eutectic point, the grain-boundary diffusion occurs. (3) But the volume diffusion has taken place above this temperature, and as the result of the formation of either solid solution or eutectic, the diffused zone melts out.

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The running quality of molten aluminium, whose purity is about 99.7%, suddenly decreases by an addition of iron up to about 0.5%, slightly decreases from 0.5 to 1.0% and considerably decreases by 1.5% addition, but gradually increases from 1.5 to 2%. It may be considered that the influence of the solidification range on this quality is observable by about 0.5% addition and is greatest by 1.5% addition, but gradually decreases with an further addition of iron. Those results were obtained under the following condition: the maximum heating temperature 850° and the superheating temperature about 50°.
The influence of the maximum heating temperature on the running quality of the molten aluminium depends on the pouring temperature: when the superheating temperature, i.e. the difference between the melting point and the pouring temperature, is over 55° the running quality of molten aluminium is superior in the following order of the maximum heating temperature, 850°, 900°, 800° and 750°, but when the superheating temperature is below 45°, the quality is superior in the order of 800°, 900°, 850° and 750° In the neighbourhood of the superheating temperature 50°, the influence of the maximum heating temperature is not so great.
In these experiments, the temperature of the metallic mould for the measurement is about 70°.

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For the purpose of finding Al alloys, which possess strong resistance against corrosion and high hardness for dental use, Mg, Si, Cu, and Ag also were selected as the additional elements; because their properties are known to strengthen the material and not to weaken the corrosion resistance of Al. Various tests have been made on these Al alloys, and the best results were obtained from the alloys containing these elements;-- 4% Si and 3% Mg; 4% Mg and 3% Cu. These alloys were not ideal, but nevertheless suitable for dental use, because of their good corrosion resistance and considerable hardness.

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