Precipitation process of Al-Mg-Si alloys during ageing was investigated by measurements of specific heat and by electron microscopy.
Specific heat-temperature curves were obtained during reheating after various age-hardening treatments in four kinds of approximate pseudo-binary Al-Mg₂Si system alloys; Al-0.60wt%Mg₂Si-0.14wt%Mg, Al-0.99wt%Mg₂Si-0.06wt%Mg, Al-1.31wt%Mg₂Si-0.06wt%Mg, and Al-1.08wt%Mg₂Si-0.02wt%Mg.
The results were discussed in comparison with those obtained by electron microscopy. Three portions for heat evolution and other three portions for heat absorption were detected on the specific heat-temperature curves of as-quenched alloys. The former portions were represented by the formation of acicular G. P. zones, rod-form β' precipitates, and tabular β precipitates. The latter portions were represented by the re-dissolution of the G. P. zones, β' and β precipitates. The effects of ageing temperature and time on the above heat evolution and absorption were examined to investigate the precipitation process of these alloys during ageing. The difference between β' and β precipitations was distinctly observed by the specific heat-temperature curves in comparison with the results obtained by electron microscopy. Clustering of the solute atoms or formation of the G. P. zones were found to occur during the process of quenching or just after quenching before specific heat measurements.

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The study on pore structures of Al-anodized films has generally been made by electron microscopy measurements.
The determination of pore structures by gas adsorption isotherms has widely been utilized as a method useful for quantitative explanation of the character of surface for a large number of materials such as catalysts.
The ethylene adsorption isotherms at -183°C; was applied by Burwell, Sumdsky, and May to the determination of surface areas of aluminum foils which had been aubjected to various etchings and anodic treatments. The results obtained by these investigators corresponded well with those of experiments by electron microscopy.
The surface area was calculated from the B. E. T. equation on the basis of the nitrogen adsorption isotherms at -196°C; for aluminum foils which had been subjected to various anodic treatments. The pore-size distribution curves of aluminum anodized films were determined by the Inkley method.

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Turning tests of 2011 (T8) aluminum alloy were carried out and an attempt to evaluate the free-machining properties of the alloy was made under the following conditions: cutting speed: 25300m/min., feed: 0.020.32mm/rev., and depth of cut: 13mm with high speed steel tools having the side rake angle of 0, 10, and 30. It has been observed that the number of chips (N) contained in 100g of cut varied from 1 to 10⁶, according to the cutting conditions. At a constant speed, N decreased to the mininum of 1 (corresponding to the formation of stringy chips) with increasing feed, and then increased again to reach a nearly constant value. Thus, when N was plotted against feed, there appeared a discontinuity, i. e., there existed some critical values of feed for the formation of discrete chips. The range of feed for forming continuous flow type chips became wider with the increase of the cutting speed and more markedly with the increase of the side rake angle. Chips were always broken at a rvey low cutting speed andat a small side rake angle.
Based on the above observations, procedures for explaining the machinability of 2011 aluminum alloy was discussed in terms of the critical feed. It was proved that the number of chips for a constant amount of the material cut can be adopted as a criterion of machinability from the standpoint of chip treatment.

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Studies were made on the formation and corrosion resistance of boehmite films on various kinds of aluminum alloys and also on the effect of alloying elements on such formation and corrosion resistance.
The following results were obtained:
(1) The thickness of boehmite films formed on various alloys (except for 5052 alloy) in boiling 0.5% triethanol amine solution for 60min. was smaller than that of high purity aluminum. This tendency was particulary remarkable in 4343 and 5005 alloys. Whereas, the film thickness of 5052 alloy was larger than that of high purity aluminum, but the difference between the both was largest in case of 15 minutes treatment.
(2) The order of corrosion resistance among various aluminum alloys with boehmite films well agreed with that among untreated alloys. Namely; high purity aluminum and 5052 alloy were the highest; 5005, 5083, and 6063 were the second; and 2017, 2024, and 4343 were inferior.
(3) In general, the addition of alloying elements to aluminum tended to decrease the boehmite film thickness. This tendency was particularly remarkable in the addition of Zn element.
(4) The addition of alloying elements to aluminum tended to decrease the corrosion resistance of the boehmite film. This effect was little in Mg, Mn and Cr addition, but was remarkable in Zn addition.

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Studies were made on the effects of temperature on the formation and corrosion resistance of boehmite films on aluminum by treatments in aqueous sulution and water vapor. The experiments were conducted by measurements of the film thickness, electron microscopy, electron diffractiometry, X-ray diffractiometry, and corrosion resistance.
The following results were obtained.
(1) The thickness of the film formed on aluminum in deionized water at 70°C or higher was different from that formed at 60°C. The former film had the same thickness, independent of temperature, except for at the initial stage of formation.
The X-ray diffractiometry revealed that the film consisted of bayerite at 70°C or lower, amorphous substances at 80°C or higher, and boehmite and bayerite at 100°C.
(2) In triethanolamine solution, the temperature gave a remarkable effect on the film thickness and the film was thicker with the rise of temperature. As the results of X-ray diffractiometry, it was found that the film in amorphous state when formed at 6090°C, but consisted of boehmite at 100°C.
(3) In ammonia solution, the film was thicker with the rise of temperature at the initial stage of film formation. After 1hr., however, the film formed at 80 and 90°C showed the maximum in thickness and high corrosion resistance. The X-ray diffractiometry revealed that bayerite was detected in the film formed at 90°C or lower, and bayerite and hoehmite in the film formed at 100°C.
(4) In water vapor treatment, temperature rise had a little effcet on the increase in the film thickness on alloys, but the film on the high purity aluminum was made thicker with the temperature rise, which increased the content of γ_s-phase in the film.
However, there were no significant effects of treating temperature on the corrosion resistance of the film.

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The surface roughness in drilling is generally much greater and more irregular than the theoretical roughness.
It is said that the reason for this is due to the deposited metal on the margin or the built-up edge. In drilling of aluminum and its alloys, it seems that the state of finished surfaces varies with the kind of material.
This paper describes the experimental investigation on the mechanism of generation of scratches and built-up edge on the finished surfaces by observing the surfaces of four kinds of aluminum alloys. It was made clear that the heat-treated-materials such as 17ST3, 24ST3, and 61ST3 were mainly affected by the deposited metal on the margin, and 56SH was mainly affected by the scratches generated by the built-up edge on the outer corner of the cutting edge.

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