The absorption phenomena of nitrogen by molten iron alloys (Fe-Cr, Fe-Mn and Fe-Ni binary alloys) were studied and the following results were obtained.
With the increase of additional percentage of Cr or Mn to Fe, the saturation value of N₂ increased from 0.039 Wt.%N₂ in pure iron(at 1600°) up to 4 Wt.%N₂ in pure Cr or to 1 Wt.%N₂ in pure Mn (at about each melting point). In the case of Fe-Ni alloys, on the contrary, the saturation value decreased with the increase of Ni and the alloys containing over than 80%Ni hardly absorbed N₂.
The curves representing the relation between the saturation values and compositions are upward concave as shown in Figs. 2,4 and 6. These relations could be explained satisfactorily by the theoretical formula (5) or (6) derived from the statistical thermodynamics under the same conception formerly reported.
One of the main conclusions obtaind from the comparison between experimental results and theory is as follows: From the standpoint of atomic arrangement, the metal atoms which have large affinity to N-atoms congregate more than the mean concentration of the alloy around absorbed N-atoms. That is,Cr or Mn atoms congregate around N-atoms in Fe-Cr or Fe-Mn alloys,and Fe-atoms congregate in Fe-Ni alloys.

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The experiments on the absorption of nitrogen by molten Fe-C (0 to 3.5 Wt.%C) and Fe-Si alloys (0 to 31 Wt.%Si) were carried out according to the experimental procedures formerly reported, i.e. ,the saturation values,absorption rates etc.were measured.
On Fe-C alloys,the satuation value of N₂ decreased with the increase of C%,as shown in Fig. 2.
In the case of Fe-Si alloys,the relation between saturatin values and Si% is somewhat abnormal as shown in Fig. 4: That is,with the increase of Si% the saturation value increased at first,and then decreased; The value reached a maximum at about 0.5 Wt.%Si ; From 14%Si (which correspond to Fe₃Si composition) above,the value again increased.
From the consideration of these results, the following suggestion was acquired that the structure of molten state (quasi-crystalline) of these alloy differs from that of Fe-Ni,Fe-Cr or Fe-Mn alloys formerly reported. In Fe-C and Fe-Si alloys, the arrangement of atoms is not at random and some regularity seems to exist even in molten state.
The effect of alloying elements on the rate of absorption of N₂ was also discussed. The rate decreased by the addition of Ni to Fe, and increasd by that of C,Si,Mn and Cr.The absorption rate coefficients (K) are tabulated in Table 1, assuming that the absorption of N₂ is the reaction of the first order.

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The process of sintering was studied tudeid on a mixture of copper powder and nickel powder,which are soluble in each other in all proportion,by the X-ray back-reflection method and by the magnetic analysis. The relation between the alloying grade and the sintering time was obtained at various temperatures under various applied pressures ranging from 9 to 28 ton/in². It is concluded that the sintering velocity increases at first with the applied pressure,but the rate of increase decreases continuously,until it reaches a constant value at the pressure of 20 ton/in²;after this pressure is attained, the velocity retaines a constant value for further increase of pressures.From the obtained date the activation energy of intergranular diffusion between copper and nickel was also computed.

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It is not yet determined whether in the mechanical mixture of powder of metals which form a eutectiferous alloy by melting the eutectic reaction takes place on heating course at the normal eutectic temperature or not Therefore the present authors have attempted to make this problem clear.
By using compressly formed specimens made of the mixture of powdery metals of simple binary eutectiferous system,the thermal changes of it was measured by the differential thermal analysis. And it is observed that such a mixture begins to melt at the eutectic temperature just like as the case of eutectic alloy made by melting.
The thermal behaviour at the contacted surface of two metal blocks which form a eutectiferous alloy by melting have also been studied. When they are heated at higher temperature than the eutectic point,the both metals melt at the contacted surface and form a layer of eutectic alloy.
From these experiments,the present authors have introduced some discussions on the interfacial reaction of contacted metals.

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In order to obtain the data useful for investigating the mechanism of age-hardening,a study was made with a Mg-Pb alloy containing 30%Pb. The alloy was,at first,quenched from 450° in water after being heated at that temperature for a week. Then the changes in lattice constants and hardness of the alloy were measured during the aging at 200°. And the variations in length and electric resistance on heating and cooling were observed.
The results lead to the following conclusions: With the progress of aging,the hardening is considerably pronounced before precipitates of Mg₂Pb are found,and the number of precipitated phase is only one (continuous precipitation) as in the case of Al-Cu alloys.

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“Rückbildung” treatments were performed in the salt-bath of KNO₂, NaNO₂, KNO₃ and NaNO₃ at 150° and 200°C,with several Al-Zn-Mg alloys;Zn 7,Mg 1;Zn 10,Mg 1;Zn 7,Mg 1,Fe 1;Zn 7,Mg 1,Si 1;Zn 7,Mg 1,Cu 1 and Zn 10,Mg 1, Fe 1 (shown in Tab. 1). Prior to the experiment,the suitable temperature for Rückbildung was determined to be 200°C,by measuring C_p (Specific Heat) at each temperature with the alloy “JO”, after quenched from 440°C. The specimens for the Rückbildung treatment were quenched from 440°C into the water,aged at room temperature (about 10°C) for 14 days and then treated.According to another report by ourselves and those of others ⁽³⁾, the age-harding of those alloys below 80°C belongs to the pseudo-precipitation type. Therefore,they must show the complete Rückbildung,when properly treated. The Vickers Hardness just after treatment, after 14 day’s re-aging at room temperature(about 10°C) and at the saturated state (more than 2 months after the treatment) were measured and the results are shown in Fig. 2∼9. They are summarized as follows;
1. The alloy “TO” (Zn 7,Mg 1),shows complete Rückbildung when treated for 10∼15 seconds at 200°C. On the other hand 150°C is found to be too low.
2. The more zinc contained,the longer time is necessary for the Rückbildung. Still,the complete Rückbildung can be realized at 200°C.
3. The inclusion of iron,up to 1%,has scarcely any influence on Rückbilding.
4. The inclusion of silicon or copper,up to 1%,prevents Rückbildung. The treatment of those alloys must be at higher temperature than 200°C, if the complete Rückbildung^** wanted to realize. Silicon prevents both aging and Rückbildung to a remarkable extent.
5. The alloy which shows the most complete Rückbildung (the lowest hardness, just after treatment) re-hardens most rapidly,but it does not follow that it will show the greatest hardness when the re-aging saturated.

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In this report, the age-hardening curves of two Al-Cu alloys, containig 3.5% and 3.9% of Cu respectively and quenched in three different ways, are compared. In quenching, the amount of quenching stress differs according to the method employed. This three different methods of quenching were ; i)quenched into 15°C water from 520°C, which may be written “ W.Q., ii) quenched into 15°C machine-oil, which may be written “O.Q.”, and iii) quenched directly into the water bath, kept at various constant temperatures and aged therin, which may be written “ D.Q. ”. The time-hardness curves, shown in Fig. 1∼3,demonstrate that the quenching effect of water varies greatly as its temperature changes, wheras that of oil varies only a little and that quenching into the 60∼70°C water is equivalent to quenching into machine-oil. The activation energy of the age-hardening in the case of oil-quenching is calculated in Fig. 4 and 5, by the process written in our last report⁽⁵⁾, and the result is shown in Tab. 1. The apparent value of the activation energy becomes larger when oil-quenched, which agrees with our common knowlege. We can say, however, that the natural temperature change of the water in our room will have little effect on the calculated value of the activation energy,when we take the roughness of the calculation into consideration, because Tab. 1 demonstrates the difference between the quenching into 15° and 60°C water. The aging proceeds more rapidly at higher temperatures ; on the contrary, the speed of hardening in the case of D. Q. will be more reduced at higher temperatures owing to the decrease of quenching stress. Thus, when these two results are super imposed, the speed of hardening, in the case of D. Q., will have the maximum at a certain temperature and will be reduced at higher temperatures and at last, becomes very small at 100°C,as shown in Fig. 6.
From those results,it can be concluded that the Al-Cu alloy will harden much more slowly at room temperature,when quenched without or nearly without stress.
No difference can be detected between the streaks in the Laue photographs of the two specimens of different quenching methods ; one, quenched into water and another, into 150°C oil. Therefore, the fact that the cluster appears on the (100) plane of the aluminium lattice whether the quenching stress exists or not shows that this is required from the crystalogrpahic reasons.

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In our last report, we classified age-hardening into two types; non-precipitation and precipitation. Hereafter, we shall use the word “pseudo-precipitation” instead of “non-precipitation”, in order to avoid confusion. It has been guessed as the result of our research, it is believed that all the ageing-phenomena in binary alloys may proceed in such a way as to agree with the “Austin-Rickett’s formula”;\dfracp1−p=Ktⁿ, which is given in the case of the nucleation and growth-process in steel. The only difference between the pseudo-precipitation type and the precipitation type seems to be the difference in “n” in the above formula ; “n” is nearly unity in the case of the former and other than unity in the case of the latter. Our research has been directed toward proving whether or not this is true in every case.
Here,two new cases are reported. In the case of the Cu-Be (Be 2.5%) alloys ageing below 350°C belongs to the pseudo-precipitation type and “n” is found to be nearly unity,whereas,the time-hardness curve above 350°C have quite different forms (Fig. 1, 2). The hardness-time curves near 300°C are not completely hyperbolas as in the case of the Al-Cu alloys, because both types of ageing are partially superimposed in this alloy. The activation energy of the age-hardening of the Cu-Be alloy is calculated to be 7,000 Cal/Mol. The time-hardness curves of the Al-Zn-Mg alloy below 70°C are also observed. It is already known that this alloy shows the pseudo-precipitation type hardening, below 80°C. In these cases, however, as shown in Fig. 4-8, the agreement with the Austin-Rickett’s type formula is not sufficient. The relation between in\dfracp1−p and t (t: time, p: degree of hardening), in most cases, shows nearly parallel lines, the inclinations of which (corresponding to “n”) are 0.95-1.03, i.e. are nearly unity. The fact that whether the alloys are situated on the Al-MgZn₂ pseudo-binary line or not seems to have no influence on these relations. The activation energy, roughly calculated, is about the same value as that of the Al-Cu alloy in the case of the pseudo-precipitation hardening.

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The boundary conditions of Fick’s equation were obtained by using the rate of reaction between decarburizing gas and carbon atoms in austenite, and the results from these equations were compared with experimental data.
The reactions between decarburizing gas and carbon atoms in austenite are represented by the following equations: & C (in γ-Fe)+H_2O \ ightleftarrowsCO+H_2+(γ-Fe),
or & C (in γ-Fe)+2H_2O \ ightleftarrowsCO_2+2H_2+(γ-Fe), and C (in γ-Fe)+2H₂\ ightleftarrowsCH₄+(γ-Fe). The decarburizing process occurring at the surface may be separated into the five steps, the slowest of which will determine the rate of the over-all process. It was pointed out from experiments that the reactions on the surface were the factor determining the over-all rate,when the velocity of gas flow was suitable. Then,the number of carbon atoms reacting on the surface is given by \[\stackrel→k=A·a₀f(p)·e^−Q⁄RTC·N^2⁄3 atoms·cm⁻² sec⁻¹,\]
where a₀ is specific activity of a carbon atom in austenite, N the number of atomes per cc ; f(p) a function of the pressure of the reacting gas,C the atomic fraction of carbon,and A a constant. The number of atoms moving to the surface through a cross section of 1 sq. cm is given by \[N·D·\frac∂c∂x atoms cm⁻² sec,\]
where D is the diffusion constant of carbon.Thus,the obtained Fick’s equation is: & \frac∂c∂t=D \frac∂^2c∂x^2;  at t=0, C=C_O, \left(\frac∂c∂x+hC\ ight)_boundary=0,
& and  h=A ·a_0 ·f(p)e^-Q/RT/DN^1/3
The results of this equation were discussed, comparing with experimantal data. The fact that decarburization ratio increased as the content of water vapour in hydrogen,and the effects of the thickness of sample on decarburization ratio and also on carbon distribution of sample decarburized in hydrogen, can be reasonably illustrated by the equation. The values of both the diffusion constant and activated energy calculated from the solution by using our experimental data agree well with Mehl’s data,but not with those of Bramley and Naito. This discordance would be due to the fact that the latter did not consider the reaction on the surface.
Our result shows that the principal reaction on the surface is represented as : \[C (in γ-Fe)+H₂O→CO+H₂+(γ-Fe),\]
and the rate of the reaction is \[\stackrel→k_(H2O)=5.4×10²⁹P_(H2O)^0.9·(C)e^{−57600⁄RT},\]
where P(H₂O) is the pressure of water vapour in hydrogen,in atmosphere : and (C) is the atomic fraction of carbon at the surface.

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By adding carbon to chromium-molybdenum steel containing 1.14%Cr,0.21%Mo, 0.17%C, eight specimens with different carbon contents were prepared. The normal transformation points of these specimens were determined by measuring the therma expansion with differentia dilatometer.
The A₃ points of these steels gradually decrease as the carbon content increase, though A₁ point is nearly constant.
The effect of carbon on the transformation points due to the maximum heating temperature and the cooling rate was studied by magnetic analysis. As the maximum heating temperature or the cooling rate increases the transformation points are markedly lowered, resulting in self-hardening. The self-hardening ability increases as the cabon content increases up to 0.75%.
The hardeness of the chromium-molybdenum steel increases as the cabon content increases up to 0.75%. The hardness of oil-quenehed or air cooled specimens from different high temperatures was studied. The change of hardness due to the tempering of oil-quenched specimens were also measured. It was found that considering hardness only, the most suitable oil quenching temperature may be 850°C.
The microstructures of these specimens cooled under different conditions were examined and the relations between the structure and the experimental results were studied.

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The change of phase in the quaternary system Al-Cu-Mn-Fe during solidification was studied by means of microscopic and thermal analyses. It is comfirmed that there exist 2 quaternary eutectics,3 ternary eutectics and 2 peritectic reactions and that there exist two quaternary compounds, which are named R and N′.The compound R crystallizes peritectically by the reaction ; Melt+FeAl₃. The compound N′ crystallizes in the same way between R and Melt,containing Al,Cu,Mn and Fe. The constitution of R and N′ is regarded as being Al₂O Cu₃Mn₃Fe₇, Al₂₃Cu₁₅Mn₃Fe₈, respectively ; Their crystal structures may be reported later. Explanatory representation of the change of phases during solidification and the reaction diagrams of solidification are constructed.

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Various sort of “Zamak” (Zn-Al-Cu alloys) have been prepared with the zinc of various purities produced in this country and the change of length as well as the change of the impact value and the hardness of the specimens during 95°-steam test have been measured.
The re-electrolysed zinc A, having the purity of 99.99%, proved to be suitable for the preparation of all sorts of “Zamak” without decaying phenomena,The zinc B, having the purity of 99.98%,may also be used for Zamak,if a suitable amount of magnesium is added.
As the Zamak 3 proved to be least sensitive to the decaying phenomena amony the alloys tested some what lower grade electrolytic zinc may also be used for this alloy.
The effect of cadmium on various kinds of Zamak have been studied and it is shown that the addition it not favorable to the decaying phenomena, especially in the range of 0.3∼0.5% of cadmium.

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The die-casting alloys,belonging to the Zn-Sn system have been prepared using the electrolytic zinc (99.95%) and the distilled zinc (98.5%) respectively produced in this country, and the change of length as well as the change of hardness of the specimens,due to the 95°-steam test,have been measured.
The alloys belonging to the Zn-Sn binary system or Zn-Sn-Cu system showed to be less sensitive to the decaying phenomena,compared with the “Zamak”.The low grade zinc may be used safely for the preparation of these alloys.If the aluminium is added,however,to the above alloys,marked decaying phenomena takes place,and it is difficult to prevent the said phenomena with the addition of magnesium to the alloys.

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Using the home-made zinc,which has the purity of 99.98% (Pb=0.008%) and adding small quantities of magnesium,manganese and chromium, various sorts of a “Zamak” have been prepared and the change of length as well as the change of impact value and hardness of specimens during the steam test have been measured.
As is well known,the addition of magnesium proved to be effective for the prevention of decaying phenomena of all kinds of “Zamak”,the necessary quuntity of magnesium was found to be 0.03∼0.06;excess magnesium made the alloys brittle and decrease flowability.
The addition of manganese and chromium especially chromium,has been found to be more effective for the prevention of the said phenomena,
If the suitable amount of magnesium and manganese or magnesium and chromium are added to the alloys,decaying phenomena of “Zamak₂” which is difficult to prevent with the addition of magnesium only,may be prevented almost completely.

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From the results of studies on the running quality of molten binary aluminium alloys containing copper up to about 33%,the authors have recognized that the solidification temperature range is one of the most important factors governing the running quality of binary alloys, just as A. Portevin and his collaborators formerly descrived in their papers,but found it is insufficient to make the values of the running quality directly correspond to the solidification temperature range in the equilibrium diagram for clarifying the nature of the running quality of the molten alloys rapidly cooling in the measuring canal.Therefore,the authors conducted the systematic and detailed studies on microscopic structures of the cross sections of the running quality test specimens and confirmed that it is necessary to take the solidification process of molten alloys flowing in the mould into concideration for explaining the peculiar phenomena in which the running qualityof the Al-Cu alloys takes minimum value at 4%Cu.

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For this purpose,the cementations of silicon into iron or copper using silicon tetrachloride and hydrogen gas was studied. On account of large vapour pressure of silicon tetrachloride,it vaporises easily. Hence the mixing ratio of silicon tetrachloride and hydrogen gas could be controlled. The larger the mixing ratio of silicon tetrachloride to hydrogen gas,the thicker the depth of diffusion, and good cementation in iron was obtained above 40%. The suitable treating temperature was above 900°C in iron and 800°C in copper, if the treating time was longer than 2 hours in iron.

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Hitherts, in order to obtain the corrosion velocity, weight decrease has been measured by frequent interruption in corrosion time.
In this paper, the corrosion velocities of tin in various corrosives were measured by intermittent and continuous methods to compare how differences exist between them.
Results obtained shows that the intermittent method with suitable calibration can be applied to measure the corrosion velocity, and it has better reproducibility than continuous method.

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The corrosion of elektron AZM in ethylated gasoline was researched, and the following results were obtained :
1. Elektron was corroded in ethylated gasoline only when the gasoline contains some water.
2. Ethylated gasoline containing water always corrodes the elektron, but the corrosion can be prevented by a suitable protective treatment.
3. Ethylated gasoline washed by a large amount of water decreases its corroding power.
4. Ethylated gasoline containing aqueous salt solution shows the vigorous attack on the elektron, and it cannot be prevented by ordinary protecting treatment.

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The determination of nickel in high cobalt alloy and cobalt metal was Studied. Nickel less than 10% must be precipitated and estimated with dimethylglyoxime by means of cyanide-aldehyde method, and that less than 0.3% in cobalt metal must be estimated colorimetrically with dimethylglyoxime. 0.001% nickel in cobalt is determinate by this colorimetrical method.

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