These studies have been carried out paying the special attension to the heterogeneity of deformation and using the etching pit method together with other conventional methods. Cold-worked state: -Sub-grains are already formed in the cold-worked state due to heterogeneity of deformation. The sub-grains are found most prominently in the neighborhood of the main boundaries and the boundary of zone affected by adjacent grains. They have generally two types; (1) relatively large blocks, and (2) fine blocks smaller than 10^-4cm.
These sub-grains which are accompanied by large internal stress and some crystal rotation become prominent with an increase of the rate of working, and finally type (1) is replaced by type (2).
In the metals heavily worked by rolling, a banded structure parallel to the rolling direction is found by macroscopic etching. These banded structure on the specimen surface is due to the different ratio of the frequency of crystal planes near (111) to crystal planes near (100).
The ratio is small in light bands, but large in dark bands.
Recovery: -When metals having the above-mentioned structures are annealed, the recovery without prominent structural change is recognized primarily. And the following characteristics are found; (1) the interal stress in fine blocks is relieved, and these low-stress blocks grow by the stress-induced boundary migration in the large block, (2) numerous polygonization walls are formed, (3) sub-boundaries in the cold-worked state become more distinct, (4) mechanical and physical properties are recovered markedly, (5) although they are very slight there are some structural changes and increases in micro-hardness, which become prominent with an increase of the rate of working. The results mentioned above will be theoretically discussed in the 3rd report.

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Annealing of cold-worked metals at proper temperatures produces recrystallization followed by recovery and growth of these recrystallized grains. They have the following characteristics:
Recrystallization-(1) Nucleus boundaries appear around the places where recovery has been Perfect in a large block. (2) The heavier the working, the easier the recrystallization occurs. The size of nucleus becomes smaller, the number of it increases, and the size ratio of nucleus to sub-grain decreases with an increase in the rate of working. (3) The nucleus size in the lightly worked state is approximately equal to the sub-grain size, and that in the heavily worked state can grow up rapidly to the sub-boundary by the action of numerous polygonization walls. (4) At the beginning of recrystallization, the recrystallization boundaries lack in clearness. (5) The grain size of recrystallization is a unique function of the rate of working. (6) The higher the annealing temperature, the lower the value of micro-hardness immediately after the recrystallization. (7) There are no recrystallization nucleus in the metals cold-tensioned more lightly than 20%, but they are recovered by stress-induced migration of already existing boundaries. (8) At the beginning of recrystallization there is found a large local difference in micro-hardness and in strain-relief at etching pits in the heavily worked metals as well as in the lightly worked ones. (9) The banded structure is not subject to any prominent change from the recovered state, and it remains until the next coarsening stage.
Growth of recrystallized grain, which was conventionally called "secondary recrystallization" or "coarsening", is customarily considered to occur after a certain incubation period. But, actually, the growth proceeds already in this period. Each recrystallization grain is an ordinary unit in this growth which depend mainly on the capillary tension of polygonization walls in respective grains, and each process is finished in a relatively short time.
In this case, the growth of grain having a crystal plane near (100) on the specimen surface is prominent along the rolling direction, and that of grain having a crystal plane near (111) is prominent in the perpendicular direction. The frequency of a crystal plane near (111) on the specimen surface increases a little owing to this process.
Thus, the duty of polygonization walls is important at the initial stage of this growth, but the analogous effect as seen in the ordinary grain growth become gradually prominent. When the grown-grain size reaches 10 or more times of average recrystallized grain size, the rate of growth increases rapidly by the effect of ordinary grain growth. This is the coarsening which takes place at first preferentially along the rolling direction.
The original boundary in growth process mentioned above needs some time for its perfect disapperance after growth.
To the above two stages of growth the auther, for convenience sake, has given names the "short range annexation" and "long range annexation" according to their mechanisms respectively.
Lightly worked metals show quite different appearances because they have no short range annexation and have relatively large nuclei. Metals cold-tensined smaller than 20% go directly to the coarsening. The rate of these growths increases with the decrease of impurities.
The results mentioned above will be discussed theoretically in the 3rd report.

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It is considered that the stored energy in a cold-worked metal is due to (a) piled-up groups of dislocations, and (b) vacant lattice sites and interstitials formed by moving dislocations. Dislocations in the piled-up group build up a sub-boundary (large and small fragmentation boundary) even in the cold-worked state by their mutual repulsive forces. The probability of the building-up is prominent near the grain boundary and the boundary of affected zone due to adjacent grains, where the stored energy is large. The recovery which appear on annealing such cold-worked metals is due to the disappearance of products (b) and (a) mentioned above. The disappearance of (a) followed by that of (b) occurs according to an annihilation of unlike dislocations and to an alignment of like dislocations. Numerous polygonization walls formed in this way cause some structural change and a slight increase of micro-hardness. These polygonization walls, due to a restriction of climbing motion for each dislocation, are still imperfect and in the high energy state, however, the effect increases with a decrease of the annealing temperature and with an increase of the rate of working. Such imperfect polygonization walls play an important role in the generation of a recrystallization nuleus which has hitherto been difficult to be explained by the conventional nucleation theory alone.
If the number of polygonization walls ending at the surface of a nucleus is n per unit area and their capillary tension is Γ per unit length, the critical size γ_C of the nucleus is γ_C=2α/nΓ which resembles the result of Orowan's theory. The specific surface energy α in this equation can be considered from the 2nd report to be increased gradually with an increase of the stressrelief within the interior nucleus block. From the above results it is concluded that for the critical condition to establish a recrystallization nucleus the difference of stored energy between the large high-stress block and the matrix must be greater than or equal to the total surface energy of the block.
Accordingly, there is no possibility of the formation of a nucleus in the metals worked by a rate of working smaller than what satisfies the above condition.
Thus the number of nuclei formed becomes equal to the number of the large blocks which satisfy the above condition, the latter being a unique function of the rate of working. It the size of these nuclei is smaller than that of the large blocks, their boundaries can grow rapidly up to the sub-boundary by the action of numerous polygonization walls.
Recrystallized grains formed by the above mechanism still have a number of polygonization walls, and each of the two grains having an interface boundary generally has the different number of polygonization walls ending at their interface. This difference results in a difference of total capillary tension of polygonization walls on both sides of the boundary, which may cause a short range annexation. Of course, in addition to the above mechanism, the grain grows also by an ordinary mechanism. Although, at the beginning of recrystallization, the effect of the latter mechanism is considered to be small compared with the former, the proportion of the latter will increase with an increase of the grain size and thus the final stage of growth depends mainly on this effect. The long range annexation will be done by this ordinary growth mechanism.

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The dilatation-orientation of cold-rolled aluminium sheets in the range from room temperature to 350°C was measured by the newly devised dilatometer.
The results are as follows:
i. Cold-rolled aluminium sheets showed marked anisotropy in their thermal dilatation.
ii. All dilatation curves showed two anomalous stages.
iii. There were similarities in the mode of dilatation changes, though the amounts of the changes were different.
iv. The greatest value of thermal dilatation was found in the rolling direction, and the smallest one in the direction perpendicular to the rolling.
v. The first anomalous change occurred, between 60 and 100°C without any microstructural change, but with a slight increase in hardness.
vi. The first anomalous changes were considered to be related to the recovery.
vii. The second anomalous change corresponded to the primary recrystallization. In this stage, a new grain was developed. There was an associated drop in hardness of about 45 percent.
viii. At or above 260°C, grain growth occurred.
ix. There were two softening courses, although the two may overlap each other to a certain extent.

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It is generally known that 99.990-99.992% aluminium with an impurity of 0.002-0.004% iron intentionally added is superior to 99.993-98.998% aluminium for making the grain finer and the electrostatic capacity greater.
The purpose of the experiment was to investigate the influences of small amounts of impurities usually contained in the 99.99% aluminium, such as iron, silicon, or copper, on its electrostatic capacity.
As a result, we realized that it was more desirable for greater electrostatic capacity to use copper, than to use rather harmful iron intentionally.
Hence it is said that the 99.993-99.8% aluminium foil, containing the impurities of limited amount of 0.007-0.009%Si, less than 0.001%Fe, or 0.00-0.003%Cu, is far superior to those on the free market as anode material for greater electrostatic capacity.

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It is recognized that the crystal lattices of pure aluminium and hydronalium alloy are expanded by an increase of occluded hydrogen gas; the effect is more remarkable in hydronalium alloy than pure aluminium. Namely, the lattice expansion is about 0.1% or less for pure aluminium and about 0.2% or more for hydronalium alloy.

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As the small amount of zirconium (about 0.5%) was found to be effective for the improvement of heat resistance of aluminium alloys as reported in our previous study¹⁾, the range of investigation was extended to other wrought alloys. Six alloys listed in Table 1 were selected this time. Those specimens were cold rolled 50% into sheets of 1mm thick and then kept at 300°, 400° and 500°C, respectively, for up to 100 hours during which hardness measurement was made. The results are given in Fig.2 a)-f) for the respective alloys. As they were quenched after the necessary period of annealing for hardness testing at room temperature, the room temperature ageing effect might have been involved, which would give higher hardness readings than actually were.
Thus, the experiment was carried out to clarify the matter; the six alloy specimens were cold rolled 50%, annealed for an hour at 300°, 400° and 500°C, respectively, quenched into water and then aged at room temperature, to see if any appreciable amount of hardening would take place. As shown in Fig. 1 a)-f), the ageing effect could be considered to be negligible except in the case of alloy No. 3 annealed at 500°C, as hardness testing was always finished within half an hour after quenching.
The results of the tensile testing carried out at room temperature are listed in Table 2 for the six alloys annealed for 100 hours at 300°C. Alloy No. 2 gave the highest mechanical properties among the alloys concerned, though cleep test at the temperature would be necessary to make final conclusion.

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Adding small amounts of Be or Li to Al-10%Mg alloys, Mg loss and formation of dross in melting, and oxidation in heating have been examined. Results obtained were as follows:
1) With Be added to Al-10%Mg alloy, Mg loss after keeping at 800°C for 15 hours, was not more than about 5%, but without Be, it reached about 60% under the same conditions.
2) Li gave a little favorable effect to the original alloy, however, the effect, was not so remarkable as that of Be.
3) On the surface of casting of the Be-added alloy, annealed at 400°C for 5 hours, the black film was not found.
4) From the results of X-ray examination, it was found that the black dross or black film, formed during melting or heat-treatment, consisted of Al, MgO and γ-Al₂O₃, but not of Mg-Nitride.

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The "Mold Reaction", one of the largest troubles in casting Al-Mg alloy, was investigated. The experiments consisted of appearance test of castings, tensile test after solution treatment on cast test bars and corrosion test immersing specimens in 5.85%NaCl+0.3%H₂O₂ aquous solution.
Those test bars were cast in sand molds specified in JIS or U. S. Federal Spec., and kinds of specimens were as follows:
(1) Al-Mg alloy cast in plain sand.
(2) Al-Mg alloy cast in special sand including each 2wt.% of sulphor and ammonium sulfate.
(3) Al-Mg alloy cast in sand including each 2wt.% sulphor and ammonium fluroborate.
(4) Al-Mg alloy containing 0.005% Be by means of Al-5% Be mother alloy and cast in plain sand.
(5) Al-Mg alloy containing 0.005% Be by means of Al-Cu-Be mother alloy made from Al and Cu-2% Be and cast in plain sand.
The results obtained were as follows:
The addition of Be to this alloy was effective to inhibit the mold reaction, and that of Cu-Be was also effective. The addition of ammonium fluroborate and sulphor to molding sand has some inhibiting effect, but that of sulphor or ammonium sulfate was hardly effective.

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Photometric method for the determination of zirconium in magnesium and aluminium alloys by the use of sodium alizarin sulfonate have been worked out. Using hydrochloric acid only or others, a rapid and reliable method was developed which can be applied to separate acid soluble zirconium from acid-insoluble one in many types of magnesium and aluminium alloys.
Results summarized are as follows:
(1) To 0.2 to 0.4N hydrochloric acid solution of zirconium, hydroxylamine hydrochloride was added, and then 5ml. of 0.20% sodium alizarin sulfonate, at 10 to 30°C, to make colored complex.
Absorbancies measured at 520mμ. represent constant values for 0.5 to 3 hours after coloring. Thus, zirconium was determined quantitatively in the presence of magnesium, aluminium and many others. Working range were up to 1.7mg. of zirconium per 100ml. of solution using 10-mm cell.
(2) The dissolution with dilute (1 to 1) or (1 to 2) hydrochloric acid, to separate acid-soluble from acid-insoluble zirconium in both magnesium and aluminium alloys were very satisfactory and reliable; the insoluble fraction was changed to a soluble form by fusion with potassium hydrogen sulfate.
These methods were applied to the determination of zirconium in many types of magnesium and aluminium alloys with successful results.

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In applying the brazed joint of aluminium and its alloys, it is important to know the strength of the brazed joint. In the first paper we reported the result of our test of single lapped brazed joint, the test pieces of which, however, were fractured in the parent metal.
This time we made further tests with the circular sheet specimens of 2S and 3S brazed with various filler alloys, and the results are as fallows:
The shearing strength obtained is 6-10kg/mm².
The photomicrographs of the typical brazed joint shows the existence of diffusion zones between the parent metals and filler alloys.
Especially, in the binary system the diffusion zone becomes deeper with an increase in Mg content from 1% to 2.5%, the reason of which is due to the fact that the test was done under the same condition, instead of observing the rule that the higher the Mg content is, the lower the brazing temperature should be.
Thus the Aluminium alloys, containing less than 2% Mg, will be brazed without difficulty with the filler alloys, 718, 716 and 719.

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