From the results of corrosion tests on Al-Zn-Mg alloys under various conditions, the following conclusions are obtained.
1. To discuss the corrosion characteristics of Al-Zn-Mg alloys, it is necessary to consider the interdependance between structures and corrosion conditions.
2. In general, the corrosion resistance of naturally aged Al-Zn-Mg alloys is inferior to artificially aged materials.
3. Al-Zn-Mg alloys have same corrosion resistance as other corrosion resistant Al alloys from the view point of reduction of tensile properties after corrosion, but in atmospheric exposure Al-Zn-Mg alloys are slightly attacked by pitting corrosion, and from this point it can be said that corrosion resistance of Al-Zn-Mg alloys is inferior to other corrosion resistant aluminum alloys.
4. Extrusion textures in naturally aged alloys based on Al-Zn-Mg system containing not less than 0.2%Cr or 0.6% (Mn+Cr) are attacked by exfoliation corrosion in exposure to NaCl solution with not less than 1% H₂O₂ or HCl solution.
5. Al-Zn-Mg alloys containing not more than 5% Zn are not sensitive to stress corrosion cracking, and it can be said to be safe in practice.

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High Al-Zn alloys and Al-Zn-1%Cu alloys containing 20-50%Al were hot-rolled at 300-400°C, finally cold-rolled to 0.5mm thickness and subsequently solution-treated at 370°C for 2hr. The change of some properties of these alloys during ageing at room temperature, 150°C and 230°C for up to 4 months was studied, mainly as a function of Al content.
The main results obtained are as follows: 1) Al content for wrought high Al-Zn alloys is desired to be less than 40%, concerning their workability and ductility after ageing. 2) Hardness and strength of the alloys increase with increasing of Al and of course with Cu content, but ductility decreases. 3) Ageing rate becomes maximum at 150°C among three ageing temperatures, and is remarkably affected by Alcontent and Cu addition especially in the case of room temperature ageing, namely, the rate at room temperature decreases by about 1/10 with every 10% increase of Al content in straight alloys. 4) Some countermeasures to check the unstability of these wrought alloys should be taken as in the case of casting alloys. 5) Mechanical properties of the aged wrought alloys are superior to those of casting alloys. 6) Structures of wrought alloys show much homogenious and this is thought to explain the fact that the ductility of the wrought alloys is higher than that of casting alloys. The change of microscopic structure of each alloy corresponds to the change of properties during ageing.

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Effects of phosphor and other elements added to the hyper-eutectic Al-Si alloys, containing 20% of silicon on the microstructure of alloys are studied.
The results of the experiments are summarized as follows:
(1) Excellent refining effect of primary silicon were obtained by the addition of As as well as P, when each content is not less than 0.03%.
(2) With the addition of P and As, on the cooling curves appearing the remarkable difference in comparison with other element.
(3) Electromicroscopic examination of the refined silicon with the addition of P and As revealed a ting crystal shapes.
The result of the experiments supported the hetrogeneous nucleation theory, commonly believed to be the mechanism of phosphorous refinements.

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As shown in the previous report, the rods of wrought aluminium 17S-T4 and 56S-F were of lower machinability under a low cutting speed of 37-183m/min and so this time we put then under a high speed as far as 330m/min. and examined the turning machinability about the cutting resistance, the surface roughness, the chip treatment and so on. As the machinability is said to be affected by the materials or the figures of the used tool, authors examined a high speed steel one side tool, a carbon steel and tangalloy tools which have the same dimention, and discussed the influences of the figures of tools on the machinability changing dimentions of them.
The results are summarized as follows:
1. It is found that the cutting resistances under high speed turning are nearly equal to those of low speed turning as shown in previous report, and show nearly constant values according to the materials but regardless of the cutting speed. In this case, the cutting resistances of 17S is greater than those of 56S.
2. According to the turning at a high speed, the good cutting surface near to the theoretical roughness of feed mark is obtained, even in the 17S and 56S which are not so easy to obtain the good surface by the turning at a low speed according to the plenty growth and dalling of built-up edge. The roughness of the cutting surface is improved rapidly with increase of the cutting speed, as far as critical speed of cutting, then arrives nearly constant roughness. It seems that the above mentioned critical speed of cutting may be a factor of machinability and, from this point of view, machinability of 17S is better than that of 56S.
3. When both 17S and 56S are turned at a high speed, straight chips or ribbon-like chips are introduced continuously and wind round a part of the machine or the tool, on the other hand these chips sometimes leave a scar on a turned surface.
4. The tangential force of the carbon steel tool is sleightly larger than that of the other two kinds of tools: the high speed steel and the tangalloy, whose tangential forces are not different. But it is observed that the traversing force of the tangalloy tool is very large especially when the side rake angle is small. But, in the chip treatment, the easily treatable chips may be obtained in using the tangalloy tool.
5. The suitable edge angle of the end cutting is about 10°according to the cutting resistance and the surface roughness.
6. On the tool tip figure, the cutting resistance of round nose is larger than that of broad nose, but about the cutting surface, the former is much better.
This study owed its expenses to the Scholarship Commitee of the Institute of Light Metal Foundation to which we are extremely greatful.

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As Al-Si-Cu alloys, which are used in many fields for the die casting aluminium alloy, that is, copper silumin, apt to be embrittled, especially to grow the hardspot and get worse the machinability when the iron content exceeds 2%, so much attention is paid to the iron content in casting. On the other hand, if the iron content is too little, it is said that the durability of the movable die is very affected because the die is liable to be seized. In this paper, the alloys, which are equivalent to JIS ADC12 and ADC13 and have four sorts of iron content in the range of 0.31-2.05%, are cast as the test specimen for the purpose to examine the influence of iron content on the machinability of alloy. 9.5mmφ rods are made for the turning specimen by the cold chamber 80CT type die casting machine (Toshiba Machine Tool Co.)
The high speed steel (SKH4) side tool has been used and the side rake angle is changed in the range of 0°-30°. And the RAMO-type high speed precision lathe has been used in the turning conditions as follows: the cutting speed is 75m/min, the cutting depth is 1mm, the feed is changed in the range of 0.06-0.25mm/rev and the dry cutting method is gone. The influence of iron content on the machinability of alloy is discussed by the cutting force, the unit net horsepower, the roughness of turning surface and others in this paper.

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The mechanism of adherence between the deposited zone and the surface of steel plate by the electrophoresis method are not entirely clarified in detail, so the authors intend to clarify these ambiguous points. In this experiment, a colloidal deposit on cathode plate is obtained when the solution which contains 5/1000mol/l AlCl₃ in pure alcohol as related in the report 2, are electrolyzed by D.C. with no suspension of Al-powder in the solution. In order to examine if this deposited substance can promote the adherence between Al-powder and steel plate, and to clarify the quality of this deposit, the authors made chemical-, infrared specrum- and X ray-analysises.
Moreover, we examined the influences on depositing rate by the amount of isopropyl alcohol and water which are contained as one of the main component in industrial alcohol employed for the standard suspension.
The results obtained are as follows:
1. It is certified that the colloidal substance which is obtained as deposit on cathode plate by electrolyzing C₂H₅OH-AlCl₃ solution, is Al(OH)₃.
2. It seems that the deposited Al(OH)₃ will promote the adherence between Al-powder and steel plate.
3. Under high voltage, the decrease of current density of cathode is greatly effected by the increase of resistance of deposited aluminum zone. But, under low voltage, it is more effected by the deposited Al(OH)₃. The cathode current density of the industrial C₂H₅OH-AlCl₃ solution is the largest, the suspension of atomized powder is the second and the suspension of flake powder is the smallest.
4. The depositing rate and the amounts of deposit of Al(OH)₃ vary with the amount of water in suspension. The former becomes largest with 7% water and the latter with 2-4% water.
5. Whenever the amount of addition of isoprophyl alcohol increases, the deposition rate decreases.

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