It was found, as reported previously, that the highest purity aluminium foil such as 99.998% should recrystallize even at room temperature, but it is very difficult to find out a nucleation by microscope and it may be an ultra-microscopic small nucleation or recovery phenomenon. The ordinary nucleation takes place at 180°C or 110°C in the reduction of 60% or 90% respectively. These nucleations coincided with the beginning of hardness decrease on the annealing curve.
In this paper, the authors investigated microscopically the ordinary uncleation phenomenon of 99.998% Al, tracing the same position of specimen during heating to detect a new recrystallized grain. It was found that the ordinary nucleation should take place at the primary grain boundary and particularly at the triple point of three grain boundaries in which severe stress may be much stored.

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In the Part 4 of this report, we discussed about the effects of voltage and concentration on the properties of anodic oxid film which is formed by the alternating current sulphuric acid process for 40 minutes. In succession to the preceding experiments, We examined in this report the effects of time and concentration on properties of anodic oxid film in alternating current sulphuric acid process. In this experiments, time is varied from 20 to 60 minutes, concentration is varied from 10 to 30% and the other factors are held in constant, i. e., voltage is 15V, and, and temperature of bath is 15°±1°C. The inspection methods for the properties of oxid film are the methods specified in JIS P 10431, 1951, which were used in the preceding experiments.
The results of experiments are as follows.
(1) The relation between thickness of film and time and concentration is shown by following experimental formula. (See Fig. 1., Fig. 2, Fig. 3 and Table 2.) T=(0.037C+0.056)t+0.05C+1.1 (10<C<30 20<t<60) (T=Thickness(μ) C=Concentration(%) t=Time(min.))
(2) The relation between thickness of film and electric power is shown by following experimental formula. (See Fig. 4, Fig. 5 and Table 3.) T=(0.0065t+0.09)W+0.035t+0.6 (10<C<30 20<t<60 0.6<A/dm²<1.4) (W=Electric Power (A/dm²×V))
(3) The relation between corrosion resistance and time and concentration is shown by following experimental formula. (See Fig. 6, Fig. 7, Fig. 8 and Table 4.) 1/S=a5.21/t+b5.2 (10<C<30 20<t<60) (S=Corrosion Resistance (Sec.)) Coefficients, a_5.2 and b_5.2 vary with concentration as shown in Fig. 8.
(4) The relation between abrasion resistance and time and concentration is shown by following experimental formula. (See Fig. 9, Fig. 10 and Table 5.) A=(0.21C-0.7)t-2(C+1) (10<C<30 20<t<60) (A=Abrasion Resistance (sec.))
(5)The relation between abrasion resistance and thickness of film is shown by the same experimental formula as reported in the Part 4 of this report. (See Fig. 13.) A=30T-100 (3<T<15)
(6) The relation between abrasion resistance and electric power is shown by following experimental formula. (See Fig. 11, Fig. 12 and Table 6.) A=(0.313t-2)W-2(0.7t+1) (10<C<30 20<t<60 0.6<A/dm²<1.4)
(7) Specific abrasion resistance increases with time and concentration. (See Fig. 14.)

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According to previous reports, Al-Mn alloy could be produced as the fine grain sheet by means of preheating of slab, flash annealing of sheet. The work has been carried out, in order to be of use producing fine grain 3S sheet in the industrial scale, the conditions of slab preheating, heat treatment of sheet, and cold roll reductions etc.
Results obtained are:
(1) Preheating of slab is effective to refine the recrystallization grain size of sheet. As the slab be 50kg weight and 120m/m thick, preheating may be sufficient 550°C 12hours.
(2) When annealed with the heating velocity of 15°C/min and up as preheated slab, the grain size of sheet has been 0.15m/m and less.
(3) Instead of preheating of slab, intermediate soaking of sheet is also effective to the fine grain, and it is desirable to heat higher temperature.
(4) Germination of grain brings about on the reduction range of cold rolling being between 50% to 70%. The reduction range of grain growth tends to change to lower reduction per cent as the sheet produced with preheated slab.

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Concerning the refinement of the recrystallized grain size of 3S alloy sheet, the influences of variables, that is, Mn content, casting temperature, mould temperature, and addition elements on the ingot grain size of Al-Mn alloy have been studied. Minimum grain size, in case of the ingot size 20 × 20 × 65m/m³ was attained at the following Condition; Casting temperature mould temperature Al(99.7%) 700°C 250°C Al-Mn(0.3%) 700 150 Al-Mn(0.7%) 700 100 Al-Mn(1.2%) 700 50
Moreover, 3S (1.2%Mn) added individually Fe, Si, Cu, Cr, or Ti up to 0.5% was rolled with cold reduction 95% and then annealed at 400-600°C for 2hrs. Influence of the above elements on the 3S ingot grain size and recrystallized grain size was summarized as follows; ingot grain size recryst grain size refining Ti→Fe→Si Fe→Si→Cr sup. inf. neutral Cu Cu coarsening Cr Ti

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To study the mechanism of age-hardening of magnesium rich aluminium-zinc-magnesium alloys, the following experiments were performed. AZI alloy (containing 9.98%Al, 0.75%Zn and bal. Mg), AZ2 alloy (containing 2.35%Al 5.72%Zn and bal. Mg) and AZ3 alloy (containing 0.24%Al, 7.79%Zn and bal. Mg) were prepared and the precipitation constituents of these alloys are, respectively, (Al₃Mg₄ solid solution), T (Al₂Zn₃ Mg₃ solid solution) and ζ (Zn Mg solid solution). They were solution heat-treated at 425°, 360° and 330°, respectively, then quenched into cold water. With these specimens, (1) changes in hardness, electrical resistance and microscopic structures during aging at room temperature, 100°, 150°, 200° and 250° were studied and also (2) changes in hardness, electrical resistance, thermal expansion and microscopic structures during heating from room temperature to 300° at the heating velocity of 1°C per min., were measured.
The results were as follow: (1) In natural aging, AZ2 and AZ3 were hardened to some extent but in the case of AZ1 its hardness increase was less. (2) As to the hardness when quenched, that of AZ1 was the highest (Rockwell-F 72)and those of AZ2 and AZ3 were Rockwell hardness F61. The increments of hardness of these alloys by aging were almost equal, but softening tendency caused by over-aging was considerably remarkable at AZ2, and AZ₃ and, at AZ, not so marked. (3) At every aging temperature, experimented, the incubation period of hardening of AZ2, whose precipitation constituent is ternary intermetallic compound (T) phase, was the shortest and that of AZ1 the longest. The hardening velocity of initial hardening period of AZ2 was the highest and that of AZ1 the lowest. In the case of tempering by ascending temperature, AZ3 began hardeningfirst and AZ1 last, (4) These three alloys harden by precipitation of the second phase from super-saturated solid solution, but the effect given by precipitation to crystal lattices depends on the degree of supper-saturation of the solid solution, and the hardening takes place in two stages and this fact is distinct in lower temperature aging.
The principal hardening of AZ1 was the first hardening stage and those of AZ2 and AZ3 were the second one. (5) The type of precipitation of AZ1 alloy belongs to "discontinuous type, " that is, at first, precipitation takes place along grain boundaries and, after this stage finished, at the remaining parts of grains, but those of AZ2 and AZ3 are "continuous type" ("general precipitation").
As one of the factors which causes such different types of precipitation, I propose the difference of diffusion velocity of solute atoms in the super-saturated solid solution.

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The hardening during keeped at room temperature after cold working was found when aiuminium contains some metalic impurities and a working strain was considerably given to thus alloys.

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61S and its families have begun to be used for constructing aircrafts, vessels and buildings in recent days. These alloys belong to Al-Mg₂Si alloys which include A-51S, 53S, 61S and 63S etc. in U. S. A. This report covers the explanation on the compositions, mechanical property of these alloys and the result of chemical experiments made with such alloys. With the heat-treated alloys, 6 experiments were made to investigate the effect of the compositions on the mechanical property and corrosion resistance of the alloys. Then the tensile test and corrosion test were made with those alloys. As the result, the conclusions of 7 item mentioned in the last part of this report could be given.

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The diagram of the Aluminium-Boron system has been determined by means of the special thermal analysis and microscopic examination. In the Aluminium-side, there exist intermetallic phase AlB₂, which has a small amount of solubility range to the Aluminium, and forms a eutectic with Aluminum at 649.8° and 0.56%Boron. On the hyper-eatectic composition, the liquidus line was suddenly risen up to a high temperature.

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In the 2nd and 3rd reports, one of the authors, Harimoto reported the electro-chemical properties of Al-Mg alloys (Light metals No. 3. 1951-V and No. 7. 1953-V).
We studied the electro-chemical properties of 52S alloys and reported the following results in this paper.
Samples, Mg contains 2.5% in Al, were heated at 100, 200, 300, 350, 400, 450, and 500°C.
After treatment, samples were dipped in the electrolytes of 0.5%H₂SO₄ and 0.1%NaOH.
Then the intensity current were measured by milliammeter and we measured about reduction 40%, 70% and 90% of th same samples, more those samples, immediately after polishing, after one week and after four weeks, were measured.

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In the Part 1 of this report, we discussed about the conditions in which the discolouration occurres and summarized them in three simple items. In this part, we intended to solve this phenomenon by comparing the sample which is boiled in distillated water (not discoloured) with that boiled in well water (discoloured).
The analyses of well-water indicate that P_H is 7.5, alkalinity is 301.24ppm, acidity is 17.2apm and iron ion is 0.17ppm. In comparison with this data, the analyses of service-water of Sakai City show that P_H is 7.1, alkalinity is 50ppm, acidity is 3.0ppm and iron ion is 0.05ppm.
Photo. 2 are the electron diffraction photographs of the surface of aluminum. No. 1 shows the photo. of the bare aluminum before boiling. No. 2 shows the photo. of the bare aluminum which was polished and etched in 20%HNO₃. No. 3 shows the photo. of the surface of aluminum after boiling in the well-water. No. 4 shows that after boiling in the distillated water. In comparison No. 3 with No. 4, we found the remarkable difference, but from this photographs we could find no clew of discolouration. We detected, however, that the crystalline alumina was formed on the sarface of aluminum which was boiled in the distillated water.
From the results of the Part 1 and the analyses of well-water, the factor of discolouration seemed to be the iron ion included in the well-water. Then, we examined the discolouration of the samples that was boiled in the distillated water in which the small amount of FeSO₄ or FeSO₃ was contained. The results was negative as shown in Photo. 3. Namely, no discolouration was occurred before the concentration of iron ion reached to 1, 000mg/l. As the concentration of iron ion is 0.17mg/l in the well-water, however, the discolouration seemes to be not the simple action of iron ion as above experimeht, as if iron ion may be the factor of discolouration.
Moreover, the next experiment certainly indicates that the mechanism of the discolouration is not the simple substitution of iron ion for aluminum ion. The experiment included that two aluminum samples were immersed in the well-water and conected to the each pole of the D. C. source (1V and 2V) and then boiled for 1 hour. For the results, the anode aluminum is more blackened than cathode one as shown in the Photo. 4. From this results, the discolouration seems to occur rather by adsorption than by substitution.
We measured the single electrode potential of samples refered to Pt and solutional current in boiling distillated water and well-water, etc. Fig. 1-4 shows the results. From this curve also, we could not yet point out the factor of this phenomenon.
Finally, we examined the corrosion resistance of the samples which were boild in the distillated water and well-water. Thee results are shown in Fig. 5-7. From this results, it seems to be say that the sample boiled in the distillated water is most resistant to any corrosive solution but the discoloured sample boiled in the well-watter is more resistant to the alukali solution than the bare aluminum, although it has the lowest resistance to the acid solution and 3%NaCl solution. From these facts, again, it seems to be reasonable to suppose that the blackning factor may be the iron ion.

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Investigated the surface condition of light alloys applied to the Kagoshima-maru and the Eleventh Fumi-maru after two to three years practical use.

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This report is the comparative tests of many chemical protection treatments for Mg alloys, for purposes of the saving of Se and the substitute of SeO process. The study continued from 1942 to 1944.

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This notes content standard specification of corrugated and crimped sheats, specific use of strips to standing or bathenseams, decks, eaves, and other flashings, gutters, and general use to siding.

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A description is given of present practice in the fabrication of high-purity aluminium foil used for electrolytic condenser. And the results of the author's experiments on the physical and electro-chemical properties of 99.99%Al are summarized compared with the ones of 99.9% Al in order to acquaint its property with consumers.

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