The electrichemical behavior of aluminum electrolytes was discussed with respect to the potential-current curves by means of chronoamperometry with linearly variable potential.
For this purpose, aluminum electrolytes were prepared with any one of the additives of NaF, BaF₂, CaF₂, ALF₃, and MgF₂. To some of them were further added more aluminum, but others were not.
The polarization potentials up to 1500, 2500, or 4500 mV were examined by linear scanning in for ward and back ward potentials.
The differences in polarization potentials between acid and base electrolytes were clarified and the mechanism of cathodic polarization was discussed.

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It is known that fluorides, which have been added to the flux, improves the brazeability in aluminum hard solder. However, very few reports have been published on their effects on the brazability in detail. The object of this work is to study the effects of fluorides in the flux.
Fluorides used in these studies were AlF₃, LiF, Na₃AlF₆, NaF, KF, ZnF₂, CaF₂, BaF₂, SrF₂, MgF₂, MnF₂, CdF₂, , CeF₃, and PbF₂. Each of these fluorides was added to each of the base chloride fluxes of the following compositions:
30wt.% LiCl-70wt% KCl
25wt.% LiCl-40wt.% KCl-35wt.% NaCl
and 20wt.% LiCl-50wt.% KCl-30wt.% NaCl
Dip brazing was conducted in the mixed flux kept at 605°C. The flow factor of the flux for joining specimens in each flux was measured as the factor indicating the brazeability.
These fluorides could be classified into the following 3 groups according to their effects on the flow factor
The 1st group: ZnF₂, CdF₂, and PbF₂
The 2nd group: NaF, KF, and CaF₂
The 3rd group: AlF₃, LiF, Na₃AlF₆, MgF₂, SrF₂, and BaF₂
The flux, containing the 1st group, gave high values of flow factor by the addition of fluorides in less than 1wt.% of fluorine; however, the surface of the brazed specimen was extremely dirty owing to the precipitation of metals resulted from dissociation of fluorides.
The flux, containing the 2nd group, gave flow factor increasing with the addition of fluorides up to 1.5wt.% of fluorine; however, the flow factor decreased with the further addition of fluorides owing to the rise in the temperature of liquidus.
The flux, containing the 3rd group, gave flow factor increasing with the increase in addition of fluorides; however, the flow factor gradually approached a constant value, which showed the stable state of the flux.
It was concluded that the fluorides belonging to the 3rd group were the most available to be added to the base chloride flux. The best effects were achieved by their addition in the range of 2 5wt.% of fluorine.

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The effects of addition of a small amount of gold on the recrystallization and grain growth of zone-refined. aluminum were kinetically studied.
At first, dependence of recrystallization behavior of pure aluminum on the purity (number of passes for zone refining) was examined and it was shown that the recrystallization temperature of pure aluminum was lowered with the rise of purity. It was further shown that the rate-controlling mechanism of grain boundary migration in high purity aluminum depended upon the driving force for the migration.
In the primary recrystallization where the driving force was great, the activation energy for grain boundary migration (Q) was determined to be 13.6 kcal/mol; while, in the grain growth where the driving force was small, the energy (Q) was determined to be 29.1 kcal/mol.
The low value of Q in the primary recrystallization strongly suggested that the grain boundary migration was closely connected with the fundamental process of atomic transfer across the boundaries. However, the higher value of Q in the grain growth indicated that it was controlled by the diffusion of foreign atoms even if their residual amount was as low as the order of a few ppm.
Secondly, the effects of addition of gold on the recrystallization and grain boundary migretion of high purity aluminum were investigated. It was found that the addition of a small amount of gold remarkably raised the recrystallization temperature and that the activation energy for the grain growth attained to 44.052.0 kcal/mol when it contained a small amount of gold (0.0015 0.0065 at.%).
According to the theory of Lücke et al., the results of the present experiments suggest that the binding energy between the gold atom and the grain boundary of pure aluminum is at least 12 kcal/mol. Such a high value of the energy cannot be explained by the elastic model taking into account of the difference in atomic radius between solvent and solute atoms. A chemical interaction between the gold atoms and the grain boundary was proposed on the assumption that the grain boundary was in a liquid state and the binding energy with the gold atoms was estimated to be about 5 kcal/mol from the temperature dependence of the distribution coefficient.

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The authors were greatly interested in impact properties of binary Al-Si alloys, in which size and distribution of silicon crystals were metallurgically controlled by any way such as sodium modification, phosphor refining, or solution heat treatment at 500°C for 30 240 min. The impact specimens were specially designed that each cast specimen of 55 × 10 mm had an opening on the center of its traverse section instead of a conventional Unotch.
The impact strength of Al-Si alloys was greatly increased by heating at 500°C. The fact can be explained by the decrease of stress concentration due to configurational change of eutectic Si from acicular to spherical form during holding. However, the impact strength of hyper-eutectic alloys was not markedly increased even after heat treatment. This fact may be due to the fact that there occurs little changes in configuration of primary crystals of Si during holding. The impact strength as cast alloys was decreased with increasing Si content, while that of heat-treated alloys was not decreased, but was kept constant in the ranges of 5 12%.
Small amounts of additional elements also gave slight effects on the impact strength. On addition of Na, the strength tended to be increased for as cast alloys, but it was lower than that of non-treated alloys for heat-treated ones. For alloys containing more than 15% of Si, the addition of Na or P had little effect on the impact strengths of both as cast and heat-treated. A small amount of Na addition caused a marked change in configuration of Si eutectic crystals. The eutectic crystals of as cast alloys were arranged in broomy form in a definite direction. By heat treatment, branches of the crystals were cut into pieces and were distributed in debris structures. The decrease in the impact strength of the specimens treated with Na would be attributed to the change of Si configuration.

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The surface roughness of drilled hole is affected by many factors. In the present studies, the effects of drill shapes and drilling conditions on the surface roughness of various aluminum alloys were pursued by experiments. The results obtained were as follows.
(1) The materials to be drilled were arranged in ascending order of the degree of surface roughness as follows: 24ST3 <17ST3 <56SH <61ST3. The above order just corresponded with the descending order of strengths of the materials.
(2) The effect of helix angle with a constant point angle (118°) was as follows: the surface roughness was more improved with the increase of helix angle and reached the best state at 35° of helix angle. The effect of point angle with a constant helix angle (27°) on the surface roughness was not very great, but the roughness was slightly improved outside the range of 90 130° of point angle.
(3) The surface roughness was greater with the increase in cutting speed or feed.
(4) The surface roughness was improved when the chips continously flowed in coiled form. There would be a close connection between the chip flow angle at drill edge and the surface roughness finished.

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