The corrosibility of aluminium, aluminium-base cast alloys (Al-Cu, Al-Cu-Zn, Al-Cu-Ni, Al-Cu-Si, Al-Si, Al-Si-Mg, Al-Mg, Al-Mg-Si, Al-Mg-Mn) and aluminium-iron alloys (2, 4, 6, 10, 20, 30, 40% Fe) by sulphur at 300°, 350°, and 440° (boiling point of sulphur) was studied by weight difference due to corrosion. The alloys were placed or dipped for 5 hrs. in vapour or in boiling sulphur. The aluminium-base cast alloys were not corroded to an appreciable degree, as in the case of pure aluminium, and aluminium-rich alloys were also passive, but they were susceptible to corrosion with increasing quantity of iron in aluminium.
In order to bring out some lights on the nature of this passivity of aluminium and aluminium-base alloys against sulphur, chemical and X-ray methods of study were undertaken, and it was clarified that the uncorrosibility of aluminium and its alloys is due to their surface protection by the formation of a compact film of Al₂S₃ in reaction with sulphur.
The action of sulphur on aluminium-coated-Flodin iron and-gray cast iron was found to be severer the thicker the coating, due to cracks, which are larger in thickly coated specimens. The attack of aluminium coated irons is attributed to penentration of sulphur vapour through coarse particles in sprayed layer into the mother iron. Therefore, in the case of spraying the thickness must be in optimum and the particles in the sprayed layer must be fine and compact.
In the appendix is given a tentative diagram of the Al-S system, which is heretofore un-proposed, based on some experiments and previous work in literature. In this system there exist two kinds of compound, Al S and Al₂S₃; the former forms from liquid at 2100° and the latter, micrographically verified, by peritectic reaction (L+AlS_??_Al₂S₃) at 1100°. In aluminium side a conjugate solution forms in a wide range of composition, the monotectic temperature being assumed to be about 1800°. On both aluminium and sulphur sides, horizontal reaction temperatures, 650° and 114°, are assigned; the former was verified to be a eutectic reaction; L_??_Al+AlS, and the latter, the melting point of sulphur.
By this diagram the nature of the passivity of aluminium against sulphur can be satisfactorily elucidated.

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In order to improve the equilibrium diagram of the iron and silicon system, the authors studied alloys between 0 and 65 per cent of silicon by means of dilatometric, thermal, magnetic and X-ray analyses.
The new diagram thereby established is given in Fig. 2.
The following conclusions are drawn from the results of the present investigation;
1. The phase (Fe₃ Si, a super-structure of iron already found by Westgren and Phragmen) is forined at a temperature of 1250° by the following peritectic reaction.
melt+α_??_α'
1. A new super-lattice phase α'', Fe₁₁Si_5' found by the authors, is formed at a composition of 18.6% Si and a temperature of 1200° probably by the peritectic reaction, as follows,
melt+α'_??_α''
This phase reacts eutectically with ζ phase at 22 per cent of silicon and at 1200° and it is stable only at temperatures above 1030°, below which it decomposes into α' and ε phases.
1. The space group adopted for this phase is T¹_h and 16 atoms included in its unit cell have the following 8 point symmetries,
5:Si-1 T_h+3 V_h+1 T_h
11:Fe-8 C₃+3 V_h
1. The chemical composition of the ε phase is determined exactly as Fe₅Si₃ (23.14% Si) and not Fe₃Si₂ (25.12% Si). this phase is formed by the following reaction, _??_''+ζ_??_ε
The curie point of this compound is measured to be 85°, and the crystal structure established is a hexagonal one containing 4 molecules of Fe₅Si₃, in its unit cell, with lattice constants α=9.727₅Å, c=411₂Å, c/α=1.398₉.
1. The lattice constant vs. concentration curves of α and α' phases are shown in Fig. 8.
1. The curie point vs. concentration curves of α, α' and ε phases are given in Fig. 6.
1. Homogeneous region of the compounds, FeSi and FeSi₂, estimated by X-ray methods is about 1 and 5 per cent of silicon respectively.

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In order to observe the hysteresis loops with a braun tube, the author designed a new apparatus which has a retardation circuit, and it is capable to change the phase advance of eddy current in the specimen caused by the exciting alternating current.
The initial magnetization curves and the hysteresis loops were measured by this apparatus on the annealed or water quenched steels of various carbon contents. The results of the same samples were compared with that obtained by the balistic method. Of these curves, the initial magnetization curves were found in coincidence, but the hysteresis loops were not coincided so good as the former.
The magnetic hysteresis loop of the twisted mild steel markedely decrease its area until its yield point, but over its point this diminution is not noticeable.

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The present paper treats the cementation of Mo on Ni and Ni-alloys. It is known that the vapour pressure of Mo is lower than that of Ni on which Mo vapour precipitates. When a nickel rod covered with Mo powder is heated ordinarily in hydrogen atmosphere, the complete cementation is not attainable, even when conditions (heating temperature, time, diffusing agents, etc.) are changed. X-ray analysis indicated that the amount of Mo cemented on the Ni surface is proportional to the cementation temperature, but if this temperature exceeds a critical point of cementation, Ni alone cements conversely on Mo surfaces, and the Mo cementation ceases. After heating for about nine hours at a temperature lower than the critical point, the cementation ceases with incomplete saturation.
The complete cementation was done by the “two-stage heating” According to this method, thb cementation is performed, on the first stage heating, at the temperature (e. g. 1100°) lower than the critical point, and then the final cementation is done at still higher temperatures.
The X-ray analysis showed that the amount of Mo cemented on the surface of the sample prepared by this method is 100%, and Mo sinters in Ni down to 0.22mm in thickness (See Fig. 10).
From the present experiment, it is seen that by this “two-stage heating”, any metal of the lower vapour pressure can be cemented on another metal of the higher vapour pressure.
The critical cementation point of pure Ni is 1150° and it is raised by the addition of Fe, Cr, or Cu.

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The form of cutting edge of tools plays on important role in the mechanical working, as it is remarkably affected by the material of tool itself, kinds of steel to be cut and the heat treatment of materials. In the previous paper the authors reported the cutting force and the cutting efficiency of tool tested by an apparatus of Schiess-Defries under various cutting conditions. In this experiment, 3 kinds of steel, (1) annealed, Cr steel, (2) Ni-Cr steel tempered after quenched in oil and (3) austenitic stainless steel, were cut by 2 kinds of high speed steel, (1) 18-4-1 type and (2) Co 5_??_6% and the following problems are investigated: (1) the relation between the form of the cutting edge of tool and the cutting force, (2) the effect of the form of cutting edge on the cutting efficiency, (3) the relation between the form of cutting edge and kinds of steel tested to be cut.
The results of this experiment are as follows:-(1) main cutting force for each steel tested to be cut, is the lowest in the neighbourhood of 60° of cutting angle and the highest cutting efficiency results in 60° of cutting angle for Cr steel, 70° for Ni-Cr steel, and 50° for stainless steel, (2) front clearance angle hardly gives any effect upon each component of cutting force, and the highest cutting efficiency is found in the vicinity of 5° for each steel to be cut, (3) as the side rake angle increases, the cutting force decreases slowly and the cutting efficiency is the highest at 5° for Cr steel, 0° for Ni-Cr steel, and 15° for stainless steel, (4) as the side angle increases, the main cutting force decreases and the cutting efficiency increases as the side angle decreases.

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