The disproportionation reaction of aluminium and its halides is studied by means of a differential thermal analysis at reduced pressure, and the temperature ranging from 1, 250°K to 1, 330°K. The reaction proceed through the formation of aluminium monofluoride by the direct liquid aluminium and solid aluminium trifluoride reaction.
The aluminium monofluoride pressure versurs temperature are determined by the following equation:
2Al(l)+AlF₃(s)=3AlF(g)
logp(mmHg)=-11, 270/T+10.267.
Thermodynamic consideration is also attempted with respect to the above reaction.

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Experiments were carried out to study the welding crack sensitivity, strength and resistance to stress corrosion cracking of Al-Zn-Mg system containing 4-8%Zn, 0.6-3.0%Mg and a small amount of Cr or Zr when welded with three kinds of filler metals (Al-5%Zn-2% Mg-2%Si-0.1% Ti, 5056 and same alloy).
The findings are as follows:
(1) Among the three, the products welded by a filler metal of 5056 alloy show the minimum tendency of zone cracking affected by welding heat. Regardless of the filler metals, the welding cracks increase in inverse proporation to the decrease of Mg content in the parent metals, but are not influenced by Zn content in the above mentioned range. Welds of Al-Zn-Mg alloy in the range of higher content of Zn and Mg are apt to crack by a bending test.
(2) All of the welded products can make almost the maximum recovery of strength in 90 days of the natural aging after welding. The recovery of strength of the products welded by the filler metal of Al-Zn-Mg-Si-Ti alloy is, it is true, generally inferior but that of those welded by the same alloy is most excellent of the three filler metals, except the parent metals containing 0.6%Mg. The maximum recovery of the tensile strength of welds to the parent metals is 85% for Al-4.5-6%Zn-1.2%Mg base alloy and 80% for Al-4.5-6%Zn-1.8%Mg base alloy, and then the tensile strength of the welds is 35-40kg/mm².
(3) The resistance to stress corrosion cracking of the welds in the alloy containing both 0.17%Cr and 0.10%Zr is rather superior to that of 0.2%Cr alone. There is no fear to see any stress corrosion cracking occur in the alloy containing 4-4.5%Zn and 0.6-1.2Mg, but otherwise in Al-5-6%Zn-1.2-1.8%Mg alloy even thouth containing both Cr and Zr, if under a severe condition. It seems that the resistance to the stress corrosion cracking of the welds is inferior to that of the parent metals. Therefore, more thorough investigation is greatly required.

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Effects of hot rolling temperatures on recrystallized grain size of aluminium sheets have already been studied by many investigators, and it is generally known that the higher the hot rolling temperature rises, the finer does the grain size grow. However, these investigations were carried out on aluminium of commercial purity, such as 99.0-99.5% aluminium, and few or no systematic studies on aluminium of a wide range of purity.
Therefore, this work is undertaken to determine the effect of the hot rolling temperature on the recrystallized grain size of 99.1-99.99% pure aluminium sheets, hot rolled at the starting temperature of 400°C (finishing 340 °C), 500°C(finishing 400°C) and 600°C (finishing 450°C) respectively and cold rolled without interannealing.
The results obtained are as follows:
1) A high hot rolling temperature gives a fine recrystallized grain size in aluminium of lower purity than 99.9%, whereas it has a little effect on a grain size in 99.9% aluminium as well as in 99.99% aluminium having a cold reduction lower than approximately 85%, As regards 99.99% aluminium with a cold reduction higher than approximately 85%, when hot rolling temperature is high, the recrystallized grain size becoms large in case of a rapid heating rate in annealing, while the grain size becomes fine in case of a slow heating rate.
2) With 99.99% aluminium hot rolled at a high temperature, a recrystallized grain size increases sharply at a cold reduction over 85%, in case of a rapid heating rate in annealing, and this phenomenon shifts to a high cold reduction in the case of a slow heating rate.
3) As regards 99.99% aluminium with a cold reduction in excess of 85%, a rapid heating rate gives a large recrystallized grain size at a high hot rolling temperature, but a grain size of sheet heated at a very rapid rate as treated in a salt bath is comparable to that of sheet at a very slow heating rate.
Whereas, a rapid heating rate gives a fine recrystallized grain size at a low hot rolling temperature.
4) A hot rolling temperature also has an influence upon a recrystallization temperature. In the case of 99.99% aluminium, a low hot rolling temperature always goes with a low recrystallization temperature. This tendency becomes less pronounced as the purity of aluminium decreases. However, it again becomes marked with 99.1% aluminium. This apparently is attributable, unlike 99.99% aluminium, to a difference in the amount of cold work due to a difference in the degree of recrystallization on a hot rolled sheet.

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There are two cases in drilling. One is a semi-automatic operation with the boring machine bitted with an auto-feeder, and the other, a hand operation by skill feeding. The former belongs to a drilling machine operative with constant feeding speed as shown in the previous report, while in the latter the work is only pressed down by a force well in keeping with the thrust of material. In this paper, the boring machine is set with a feeding a pparatus so as to operate in constant drilling force, and the drilling machinability of the rought aluminium, such as, 17ST4, 27ST4, 52SF and 56SF are experimented.
The drilling resistance is measured by using the trial powermeter for two compornent of resistance, and it is found that the thrust is constantly balance with the drilling force no matter what the drill diameter is in every work and that drilling characteristics of work make appearance as a difference of the torque. Consequently, when the drilling time under constant drilling force, i. e., the time required in drilling the unit depth, S (sec/mm), is measured on the oscillo-paper of drilling resistance which is picked up from the powermeter, the torque T_q experimentaly formulates S=k•T_q^β where, even though the torque is the same in quality, the larger the material constant k and β grow, the longer time does the drilling take and the machinability gets the worse. This experiment shows that the drilling machinability can be made better in order of 17ST4, 24ST4, 56SF and 52SF, and that in a certain drilling, say, of 10mmφ under the same drilling force, the torque in the case of predrilled drilling becomes several times larger than usual cases of drilling, with the consequence that the drilling time becomes far shorter. So it is advisable to adopt the pre-drilling method particularly in drilling materials of inferior machinability.
This study was conducted with funds furnished by Scholarship Committee of the Institute of Light Metal Foundation, for which we feel deeply grateful.

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Recently the demand for aluminium alloys with a view to lightening the weight of various machine parts has been increasing in the field of the automobile and other industries. However, there are few data obtainable conerning the wear characteristics of aluminium alloys. So how some of the typical casting aluminium alloys, e.g., Lautal, Low-Ex., Y-alloy and hyper-eutectic Aluminium-Silicon alloy wear out against the same alloys and carbon steel respectively, is examined under unlubricated condition. The results are summerized as follows.
1. In discussing the wear resistance of materials, it is to be noted that wear varies with the combination of materials to be pitted against such other.
2. In the case of alloys against the same kind of alloys, the wear resistance of aluminium alloys is sometimes firmer than that of the carbon steel at relatively low speed of sliding, but as the sliding speed is increased, Lautal, Low-Ex. and Y-alloy may generate a partial welding phenomenon (scuffing) on the frictional surface. This is particularly remarkable in Lautal and Low-Ex. because the melting point of aluminium alloys is relatively low. However, it is of interest that so far as this experiment goes scuffing does not occur in hyper-eutectic Aluminium-Silicon alloy, and the wear loss of this alloy is far smaller than those of other aluminium alloys.
3. In the case of aluminium alloys against carbon steel the wear loss is very small irrespective of the sliding speed and the contact pressure. In this experiment, those combinations reveal mild wear and the surface roughness is very little.

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In the first report, the wear characteristics of aluminium alloys against the same alloys and against carbon steel ware described. In the case of aluminium alloys against carbon steel, the wear loss of each of the materials is vrey small irrespective of the sliding speed and the contact pressure. When aluminium alloys excepting hyper-eutectic aluminium-silicon alloy are combiend against the same alloys, partial welding phenomena (scuffing) can easily occur on the frictional surface as the sliding speed is increased.
In this report, frictional characteristics such as the frinctional coefficient, the surface appearance and the surface roughness. The results obtained from this experiment are summerized as under:
1. It has been thought that there are not always definite relationships between the frictional coefficient and the wear. However, in this experiment it is made clear that there exist intimate corelations between the two. In the case of aluminium alloys against the same alloys, the frictional coefficient increases along with the increasing of wear loss, especially where scuffing occurs, the frictional coefficient as well as the wear loss show a rapid increase. However, in the case of hyper-eutectic aluminium-silicon alloys against the same alloys and of aluminium alloys against carbon steel, the frictional coefficient decreases in conformity with the deminution of wear loss as the sliding speed is increased.
2. In the case of aluminium alloys excepting hyper-eutectic aluminium-silicon alloy against the same alloys, scuffing can easily occur under a high sliding speed and at high contact pressure, and surface roughness in creases. The hyper-eutectic aluminium alloys sach withhard spots coming about on the frictional surface thereon, does not generate scuffing, for the hard spots on the either alloy come into touch with each other. While in the case of aluminium alloys against carbon steel, not only the wear losse but also the frictional coefficient are very small since the frictional surface is protected by an oxidized layer.
3. Though unstable at the initial stage of wear, the surface roughness may get to the constant value when wear reaches astationary stage, and the value may be controlled according to the experiment conditions.

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The distribution of beryllium in the surface parts of solid magnesium alloys containing beryllium after heated at 300°, 400°or 500°C was studied by chemical analysis, and even further, change in the weight of the samples after heating magnesium and its alloys containing 1% of Al, Ca, La, Th and Zn besides beryllium, and still further the comparison between the distribution of beryllium in the samples after heating and that of beryllium of cast samples.
Results obtained are as follows:
(1) The weight of pure magnesium when heated at 400°C increases far more than that of magnesium containing beryllium. Slower oxidation was observed in magnesium alloys containing 1% of Al, Ca, La, Th and Zn, besides beryllium than in pure magnesium.
(2) The enrichment of beryllium is found in the superficial layer of Mg-0.005% Be after heating. This enrichment of beryllium in the surface can serve the purpose of preventing the alloys from oxidation.
(3) The enrichment of beryllium in the surface varies with elements added, that is, highly enrichment is found in Mg-Be alloys containing Al and Ca, lower in the alloy containing Zn, and scarcely any in those with Th and La. The same tendency of the diffusion of beryllium to the surface is found on castings.
(4) As the result of the study on the effect of the heating atmosphere on the mode of distribution of beryllium when heated, at the diffusion of beryllium to the surface is remarkable when heated in air. at 500°C, but only a little in vacuum and in argon. So this suggests that such diffusion of beryllium to the surface of the magnesium alloys is due to the strong affinity between beryllium and oxygen in air when heated.

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