Recent developments in the field of Magnesium alloy added with rare elements have been surveyed. First, strengthening Magnesium alloy by the addition of Zirconium. Which refines its grain-size remarkablly is described. Various methods have been tried in adding Zr to Mg alloy, but none seems to have been fully succeeded. Addition of Lithium to Magnesium was found in recent years to change its lattice type into cubic, which improves the workability of Mg to a considerable extents. Some elements are recommended to be added to this binary system to increase their strength; Zn, Mn and Al are among the elements recommended. Rare earth elements in the shape of mischmetal was known to strengthen Magnesium and several examples are considered and introduced in this article.

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The persent investigation has been carried out to study the refining conditions of molten aluminum by holding.
Adding up alumina, cryolite, aluminum fluoride, aluminum carbide which had been made in the bottom of the cell, and metallic sodium to the molten pure aluminum having the purity of 99.7%, the effects of holding of these kinds of metal as cast on the mechanical properties were studied.
Generally in spite of molten holding, the effects of additional impurities were not thoroughly vanished, the strength was slightly increased and the elongation decreased. Adding up metallic sodium to the molten metal, the mechanical properties were improved by remelting than molten holding. Adding up the cryolite bath as impurity to the molten metal, the effects of impurity were obscure.
The mechanical properties of bath aluminum that was directly produced by the cell and no molten holding treatment, were studied. The strength and the elongtion of the metal were affected by the bath composition.
The 720°C, 6-8 hours holding is better than the higher temperature holding or shorter time holding.
The causes of the lowering of mechanical properties were frequently due to the lining brick of the holding furnace. Properties of the metal were improved by remelting and holding in the furnace used suitable lining brick.

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The difference of the mechanical, chemical and physical properties in aluminum and its alloys appears to have some relation to the behaviour of hydrogen atom, which is considered to be in solid solution or to be in compound (Al H), as well as molecular hydrogen.
Although a number of investigators have studied the problem of gas in aluminum, little attention has previously been given to the authors view. In this point of view, we performed some observations upon the effect of hydrogen gas on the snb-boundary structure of aluminum single crystal, and here we will report our experimental results and the related discussions about the Lehaviour of hydrogen in deforming crystal from the view point of the theory of dislocation.

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We carried out the qualitative experiments about the relation between aluminum and gas by the two-dimentional crystalline model of a bubble raft. The results obtained from the point of view of "atomic" structure are to be shown more clearly about the effect of qases into aluminum for its plastic properties, recrystallization or grain growth etc.

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All manufacturers concerned saw the aluminum sheet ingots so often crack in the course of hot rolling that back in 1949 the writers carried out a series of experiments with a few to find out its cause and at the same time fully discussed the question availing themselves of all statistical data available then.
It was found, that the cracking often took place where there were hair cracks on its surface, while such hair cracks were chiefly caused by its shrinkage in the course of casting and that the ratio of iron and silicon had also not a little to do with it.
In short, the conclusion was that the casting condition, or the melting temperature had by far the most important bearing on this question.
On the other hand, as to the brittleness of virgin ingot, which has generally been considered another cause of the or cracking, no definite data were obtained to clarify it, because we made no systematic examination then about the influences of Na, Carbide and Al₂O₃, with which this report is naturally not dealing.

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To study the refractory brick in aluminum melting furnace, the following test was conducted.
(1) The reaction with molten aluminum and the refractory brick powder.
(2) The reaction with molten cryolite and the refractory brick.
(3) The abrasion by aluminum at room temperature.
Almost of the brick are invaded by aluminum and the metal increased silicon, iron and titanium. The other brick are invaded by molten cryolite.
However, it was found that the two kind of alumina brick are more excellent than the other brick for the aluminum melting furnace.

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We used the 30kg commercical pure aluminum ingot and rolled down to the reduction rate of 88% of initial thickness at the temperature of about 460°C, and the final temperature of product showed about 410°C.
The experiment were done on the specimens which were taken from several parts of surface and central parts of the sheet which was cooled in air after hot rolling, the elongated spots or asterism which showed the strain of material were seen in the patterns make by Laue's method using copper anticathode, on the contrary we can not seek out asterism in the pattern of the specimen which was heated to 550°C.
Furthermore, some hardening phenomenon was found in the relation between Vicker's hardness and the heating temperature, and X-ray rotation photo-graphs approached to a stste of recrystallization at higher temperature.
From these experimental result we can assume that though the normal recrystallization is produceed by heating after rolled, the hot rolling sheet may be slightly recrystallized in the stage of hot rolling.

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In order to decrease an effect of moisture in sand upon castings, it is necessary to decrease the pressure of vapour by moisture at surface of contact with metal.
For that purpose, it is required to decrease the mass of moisture added to sand, therefore we have to use sand which is excellent in workability and permiability at fewer moisture. In addition to permiability of sand, we have to soften hardness of sand and make the thikness of sand layer as thiner as possible, finally to hasten the cooling velocity of metal, with a view to making an earlier forming of solidifing film at contact surface.

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In the Report 1, Authors reported that the changes of electrode potential occure in what manner by the purity of Aluminum and the sort of electrolytes.
In this paper reports. the results that we obtained in these studies about which the electrode potential of pure Aluminum is affected in what manner by the working degree.
The Aluminum specimens supplied in this study, were 99.6% purity. These specimens were heattreated at various temperatures, namely, 180°, 350°, and 450°C. Working degree of specimenes were 40%, 70%, and 90%, respectively.
As the electrolytes, 3%NaCl+0.1%H₂O₂, 0.1%HCl, & 0.5%H₂SO₄, were used. New designed vacuum-tube potentiometer which adapted for use with this research, which have been previously reported, was employed.
Conclusion
(1) At the instance of dipping, electrode potential indicates similarly eletro-positive.
(2) By the working degree of the specimen, the electrode potential differ from each one, but the electrode potential get greater in proportion to the degree of working of specimen.
(3) Flectrode potential differ by the heat treatment.
(4) By the sorts of electo yte, the dropping ratio of electrode potential differ. Whereafter in the case of 3%NaCl+0.1%H₂O₂ the electrode potential become generally constant value.
When 0.1%HCl solution is employed, it have tendency to dropping, on the contrary 0.5%H₂SO₄ was employed, it indicats reversely the tendency towards rising up.

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The effect of the alloying elements upon the mechanical and chemical properties of Al-Mg alloy sheet, to be used in shipbuilding industry was studied in 50% cold-rolled condition.
Sheet of 1mm thickness was used for the tests; tensile testing, corrosion test in 3%NaCl aquaous solution and stress corrosion test in 3%NaCl solution with hydrogen peroxide.
Al-Mg alloys, containing 3 or 5%Mg, respectively, were considered, when either of Manganese or Zinc was added up to 1.2%. Manganese could improve strength slightly, but its effect on corrosion resistance was proved to be good. On the other hand, Zinc was found to be harmful for corrosion resistance, particularly in stress corrosion phenomena, though strength could be enhanced to some extent.
Chromium up to 0.6% was then added to Al-3 or 5%Mg-0.6% Mn alloy with or without Zinc addition of 0.8%. It was found that Chromium could strengthen the alloy until its tensile strengto would exceed 40kg/mm² and that its effect was more remarkable when Zinc was not contained. Amount of corrosion in NaCl solution could be reduced when Cr was added, unless Al-Cr compound would appear in micro-structure. Stress corrosion could also be prevented. In Al-Mg alloy, containing Zn, stress corrosion characteristics were much improved by the addition of Cr.
In conclusion, Cr Seems to be the most appropriate, Mnf ollows, and Zn will be the least suitable, for an alloying element in Al-Mg alloy system, when used for ship building purposes. When formability must be taken into consideration, Al-3Mg-0.6Mn-0.6Cr alloy seems to be the best among the alloys considered, which has tensile strength of 35.8kg/mm² in 50% cold-rolled state. More strength can be obtained in Al-5Mg-0.6Mn-0.4Cr alloy, but elongation value becomes less. Resistance to both corrosion and stress corrosion attack in these two alloys seems to be satisfiable.

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The present investigation was carried out to acertain the effect of heat treatment on the natural age hardening and temper hardening of Al alloys containing Cu and Sn which had been used for bearing materials.
As these test pieces were prepared by addition of the mother alloys (Cu₆Sn₅Cu₃Sn) and Mg to Al, the results obtained from the study of Al-Cu₆Sn₅, Al-Cu₃ Sn, and Al-Cu₆ Sn₅-Mg systems were as follows:
(1) All the alloys of these systems did not show a natural age hardening at room temperature, and the temper hardening was remarkable except the two alloys containing 2%Cu₆ Sn₅ or Cu₃ Sn. But the addition of 1.5%Mg to these two alloys gave an influence upon the temper age hardening. From these results, it was cartain that Cu and Sn were soluble in Al.
(2) By heating these natural aged alloys at 220° for a short time, the hardness increased at first and decreased, and then increased. This first hardening seemed to be a temper hardening without a certain precipitate and the second by it.

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Using Φ 125mm billets and 1000ton press, we investigated the effect of zinc, magnesium and copper on the extrusion speed of the Al-Zn-Mg-Cu alloys, and then the effect of extrusion speed on the mechanical properties of Al-Zn-Mg alloy "H. D"
The results obtained are as follows.
i) The increase of any one of magnesium, copper, zinc, decreases the safty extrusion speed and improves the strength Magnesium is the most effective of them. Copper decreases the safty extrusion speed remarkably, when compared with improvement of strength. Zinc is the least influential.
ii) The increase of extrusion speed of "HD" alloy diminishes so called "characteristics of extrusion" (that means fiberous structure and high strength), prominently with speed above 12m/min.

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Effects of working-condition include those of chemical composition and temper of base metal, kind of electrolyte, concentration and temperature of bath, kind of electric current, voltage, current density, time, dying condition and pressure and time of steam-treatment, etc. Although we will examine those effects one by one, in this report, we study at the effects of voltage and concentration in sulphuric acid process. The properties of oxid film which we test by the inspection process of JIS P. 0431, 1951, are thickness, corrosion resistance and abrasion resistance of oxid film. Results of experiments are as follows.
(1) The relation between thickness of film and electrolytic conditions is shown by following experimental formura. (See Fig. 3, Fig. 4) T=e^{(0.0176C0.657+0.0311)V} T=Thickness(μ) C=Concentration V=Voltage (Time:40min 10<C<30 10<V<20)
(2) The relation between thickness of film and amount of electric power consumption is shown by following experimental formura. (See Fig. 6) T=3.2+0.45W W=A/dm²×V (Time:40min 0.2<A/dm²<1.5 10<V<20)
(3) The relation between corrosion resistane and electrolytic condition is shown by following experimental formura. (See Fig. 7, Fig. 8) S=6.8e^{(0.0818C0.552+0.0666)V} S=Corrosion Resistance(Sec.) C=Concentration(%) V=Voltage(V) (Time:40min 10<V<20 10<C<30)
(4) The relation between thickness of film and corrosion resistance is shown by following experimental formura. (See Fig. 9) S=180T^0.253-239 S=Corrosion Resistance(Sec.) T=Thickness(μ) [3<T<20]
(5) The relation between abrasion resistance and voltage is not able to be shown by the simple experimental formura. The higher the voltage is, however, the more the abrasion resistance is. (See Fig. 10)
(6) For the relation between abrasion resistance and consentration of electrolyte, the simple experimental formura can not be also introduced. As voltage rises, the maximum value of "Specific abrasion resistance" (abrasion resistance for unit thickness of film) changes its place toward the dilute side of concentration. (See Fig. 11)
(7) As to the relation between abrasion resistance and amount of electric power consumption, abrasion resistance for same electric power consumption rises with concentration when it is below 20 per cent. As concentration rises above 20 per cent., however, abrasion resistance falles on the contrary. Then effidency is maximum when concentration is 20 per cent. (See Fig. 12)

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The cathodic protective method for aluminum and its alloys from corrosion in various electrolyte solution was studied. In general the cathodic current density of adequete magnitude applied by the external e. m. f. can fairly protect aluminum and its alloys from corrosion in various solutions except the alkali. In the case of salt solutions for example sodium chloride, :aluminum can also be protected by cathodic current, provided that the current density is not too high. If the current density exceed the limiting value, the cathodic corrosion does occur The condition necessary to protect aluminum and its alloys from corrosion in various solutions can be summerized as follows.
Table 1
Contact of aluminum and its alloys with baser metals such as zinc can also protect aluminum, for the actual measurement of the current through the circuit of these combined metals and alloys showed just the same amount as mentioned in the above table. The cathodic current of the alclad duralmin core afforded by aluminum coating is also in the range of protective condition ass hown in the above table. In fact the excellent corrosion resistance of alclad alloys can be attributed partially to the cathodic protection of the duralmin core by the aluminum coating.
In conclusion, the effect of cathodic protection of aluminum and its alloys is essentially the same regardless of whether the current is afforded by an external source or by a dissolving anode of protective metals. But one must be careful that the aluminum and its alloys has both the upper and lower limits for the proteting current in the salt solution. The current density above the upper limit produces a bad effect. Contact with a metal which is too basic to aluminum causes corrosion of the latter. For example. the contact with magnesium accelerates the corrosion of aluminum and its alloys in sodium chloride solution. The coating materials of alclad plate must supply the sufficient current to protect the core alloy, but must not exceed the critical value.
These cathodic corrosion of aluminum and its alloys is not due to the reduction of oxide film by atomic hydrogen evolved at the cathode as the case of stainless steel, but due to the cathodic production of caustic by electrolysis of salt solution by the current of so called cathodic protection.

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According to previous reports, anodic films of Aluminum have been believed to be porous.
To ascertain this, we observed them directly by electron microscopy, and concluded as follows.
In general, the films have porous and network-like structures, and they are influenced by the condition of anodic oxidation, that is, the composition and the temperature of the electrolyte and the current density.
The linear dimensions of the pores in the typical network-like structures are from 0.03 to 0.18 microns.

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Various properties of 3S sheet when it was heated in air furnace or salt bath and a structure of its alloy slab were examined. The results obtained were as follows:
(1) When 3S sheets, having each thickness 3.2mm (cold reduction degree 46%), 1.6mm (72%), 0.8mm (84%), were annealed in the air furnace, we found that a peculiar surface layer consisted of the very coarse grains had appeared on them. The grains of such surface layers were coasser as the annealing temperature lower and smaller as the heating velocity faster. Also the grain size was maximum near 70% cold reducion degree. In the case of salt bath heating, the difference of grain sizes between surface and inner part could not be seen and the grains were smaller than any ones of the air furnace heating.
(2) The thickness of the surface layer was very thin such as only 2% of the sheet thickness and each about 0.06mm (3.2mm sheet), 0.03mm (1.6mm), or 0.01mm (0.8mm). If this layer appeared once, it did not disappear although the sheet was rolled to 0.1mm. And even specimens with such thin peculiar surface layers exhibited "orange peal" by deep drawing.
(3) The surface layer had the higher recrystallization temperature, the lower hardness than inner part and also the distribution of hardness or grain size changed suddenly at certain depth same to the layer thickness, it was hardly etched, probably due to the homogeneous distribution of working stress.
(4) As to the microstructure of sheet, Mn compound particles in the surface layer were smaller and distributed homogeneously, but larger and heterogeneous in the inner part. Then, the dispersoid only could be seen in the inner part.
(5) The structure of slab surface chilled at the face of metallic mould exhibited the very coarse grains involving the small particles of Mn compound and no dispersoid, but the inner structure appeared with the small grains involving the large particles of Mn compound and a great number of dispersoid. The slab structure like this was proportional to the sheet structure.
(6) The sheet worked by cold rolling after preheating at 550°×15hrs exhibited the very small recrystallized grains, perhaps owing to the appearance of dispersoid in surface or inner part.
(7) The growth of the peculiar surface layer and the grosscrystallization of recrystallized grains in it were thinked separately through these results.
a) As for the growth of the surface layer, the surface is deformed by hot rolling more severely than the inner pard and softened with the heat formation by this severe deformation. This also the crystal orientations of grains are ordered gradually. By cold rolling the surface is deformed more and more with a partially heterogeneous rolling action and the crystal orientation is ordered strongly. Through this process the difference of various properties between surface and inner part will appear as described above.
b) About the grosscrystallization of surface grains, we think that a incubating coarsen property of Mn in the alloy will be a important factor for grain growth and this characteristies of Mn will be promoted by the following facters such as: the surface structure of casting, the strongly preferred orientation of grains in the surface layer with particularly severe deformation, and the working process the dispersoid do not appear through rolling period.
(8) In order to the grains, preheating prior to the finishing rolling or salt bath heating was effective.

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The studies on the effects of iron and manganese to the mechanical properties of Al-Mg 5% alloy were carried out. Iron, up to 0.5% as limit of specification, varies less mechanical properties, but decreases the excellent corrosion resistance of this alloy. Manganese increases ultimate tensile strength up to 1% present with small quantity of iron and 0.8% present with 0.5% iron, and decreases it over these contents. On the other hand manganese decreases elongation of this ductile alloy and pronounced present with iron. Manganese is effective to compensate for the detrimental effects of iron on the corrosion resistance and also of over-heating or long-time melting on the mechanical properties of this alloy. Eventually, appropriate amount (0.3-0.5%) of manganese seems to be essential to this Al-Mg 5% cast alloy.

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When light metals contact with other metals, for instance steel, it eroded especially in the presence of electrolytic solution, such as NaCl.
Aluminum alloy (52S) panels are worn with steel bands with or without various coating or insulating pastes, and submerged into a aqueous solution containing 5.85%NaCl, 0.3%H₂O₂.
In untreated (direct contact and bare) panels, aluminum panels generals gas bubbles and considerably eroded, but steel band not so eroded. When insulating cloth tape (cloth painted with paste consists of polybutene, paraffine, boiled oil, gilsonite and zinc chromate etc.) Placed between aluminum alloy and steel, the corrosion rectrogressed. Steel band eroded and aluminum alloy not affected. After the submerge over 1 month, significant lowering in tensile strength of aluminum alloy not founded.
When panels are coated with various coatings, (zinc chromate primer, wash-primer, vinyl resin primer) showed good resistance.
Between insulating paste, polybutene-boiled oil-zinc chromate type showed best results, and in coatings, vinyl type primer was best and wash primer-zinc chromate primer (synthetic resin vehicle) was the second.
It is interesting what then metals are contact directly, erosion occured at aluminum panel and produce white precipitate, aluminum hydroxide, and when metals are insulated by paste, erosion occured at steel and produce reddish ferric precipitate.

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We have examined on the effect of a corrosion prevention, especially a contact corrosion between light metal 52S panel and hot rolled steel piece, which are painting, the paste tape are holding between them.
Testing panels which are holding the narrow painting steel piece at the center part, have been immersed into the 5.85%NaCl and 0.3%H₂O₂ solution during one month.
Light metal 52S panels are painted with zinc chromate primer, asphalt type varnish, and "Vinylex" active primer (Wash Primer Type), and also steel pieces are painted with the same or enameled gilsonite paste, zinc chromate, paste, and polybutene paste.
According to our testing results, we have known the panel of the best corrosion resistane maybe the painted with 1st coat "Vinylex" active primer, 2nd coat zinc chromate primer, and moreover the enameled with zinc chromate paste. Then the best corrosion preventing paste was polybutene.

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Some test pieces were in such a way that on the both surfaces at the middle of 52S-0 sheets, bare and anodized, having 1mm thickness, 1mm. thick mild steel sheets are fixed on by means of bars rivets. The surface of the said mild steel sheets was treted in different ways, namely Zn dipping, Zn plating, Cd plating, Zinc-chromate coating and Bituminous painting. These test pieces were left wholly immersed in a bath of 5.85%NaCl+0.3%H₂O₂ solution for 3 months. Thenafter we have made their appearance as well as mechanical property tests.
As the results, it was found that the test piece having the mild steel sheet with Bituminous paint proved the best.52S sheet with anodized surface gave a some what worse result than the bare one. Needless to say, the sample with bare 52S and bare mild steel sheets was showed to be the worst.
By the way, it seems that in these contact corrosion test, NaCl testing solution with the addition of 0.3%H₂O₂ had rather too strong action.
We have to add that these tests have been effected as a part of the collaborated tests of the Surface Treatment Sub-Committee of the Ship-Building Light Metal Committee.

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Contact corrosion tests between 2S and Iron Sheet in sea-water under the various condition were carried out for 23 months.
Under the following condition even a trace of contact corrosion was not noticed.
2S Sheet: All surface pretreated with alcohol solution containing phosphoric acid was primed with Zinc-chromate primer, finished with Al-paint and then coated with bituminous paint at the contact area only.
Iron sheet: galvanized with Zinc,
On practice better result is expected by using Zinc-chromate tape between both Sheets.
Paints which is injurious to aluminum sheet such as containing compound of Cu, Hgand Pb should be avoided.

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Aluminized steel is a sheet of steel coated with aluminum and is somewhat similar in appearance to a sheet of aluminum. The weight of aluminum applied to both sides of the sheet is almost equal to a steel sheet, resulting in a coating thickness about 2.5×10^-2mm of aluminum per side. The finished product, coated on both sides, combines the surface characteristics of aluminum with the mechanical and physical properties of steel.
The coated aluminum provides the heat reflectivity and attractive appearanc; the cored steel gives the tensile and yield strength, endurance and working qualities; and the two metals together resist the combination of heat and corrosion far better than the aluminum coating or steel base alone. On the present investigation, molton aluminum is applied directly to the specimens by a hot dipping method.
After preparing a steel surface by clearing and pickling, the specimens are immersed in an aluminum bath and held there untile it is heated to the temperature (700-800°) of the bath. The specimens are then removed to permit draining of excess aluminum and allowed to cool to room temperature.
The coating will be formed on steel in varying thicknesses from 1.5-2.5×10^-2mm and consists of an outer layer of relatively pure aluminum and an inner layer of iron-aluminum compound (FeAl₃) containing approximately 40-60% aluminum.
The lower the temperature of immersion, the thicker is the pure aluminum and the longer the time of immersion at any temperature, the thicker is compound layer. The exess compound layer gives the harmfull effect on the mechanical and workable peoperties of aluminized steel. To prevent the growth of the compound layer, silicon copper and zinc in effective amounts from about 5-13% are added individually to molten coating bath. Carbon content in steel controlled the diffusion layer to a somewhat greater extent than does composition of the molton coating bath.

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In applying light metals to shipping, we tried to build the light metal life-boat which is one of the most suitable application of light metals. In regard to this attempt, some manufacturers carried out already, but our boat is the largest one and produced experimentally under the subsidy for studies of science of Educational Department.
Although the details of its specialities are as undermentioned, specially it is remarkable that its weight has been saved more than 700kg compared with wooden or steel one. And then, if more investigation and improvement will be carried out on itsstrength and construction, the weight may be reduced 150-200kg moreover. On this paper, we discussed mainly on her strength and construction.

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To study the mechanism of age-hardening of magnesium-rich zinc-alloys, these experiments were performed. zinc-magnesium alloys containing 8.37% and 4.22% zinc by weight were solution-treated, respectively, at 340° and 400°, then water-quenched. On these speciment, (1) changes in hardness, electrical resistance and microscopic structures during aging at 100°, 150°, 175°, 200° and 250°, (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 are as follows: (1) The age-hardening of these alloys depends, principally, on strains caused by precipitation of the intermetallic compound (MgZn) from super-saturated solid solution, but, at the initial stage of age-hardening, partially, on distortions prio to precipitation. (2) The degree of hardening by precipitation must be considered as the function of the degree of supersaturation of matrix, that is, the more the matrix is super-saturated, the more the hardness increases by a quantity of precipitation. (3) According to change in microscopic structures, precipitation takes places simultaneously at all parts of every grain, that is, independently on grain boundaries. The type of precipitation is the "continuous type".

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Thermo ouples were made by deformed Mg rod and annealed Mg rod, and were heated at one junctions, and the crystal recovery and the recrystallization phenomena were researched by measuring the change of the value of the thermo-electro motive force, hardness value, and X-rays analysis.
1. The more increased degree of deformation, the more the value of the thermo-electro motive forces
2. In each curves of the thermo-electro motive force, two crooks (abnormal changes) were recognized. And on the first crook, the temperature range of crook was 120°C-250°C and on the second, it was about 200°C-300°C.
3. Till the beginning of the first crook, the curves arose straight as the temperature arose and were reversible to temperature, and after the begining of it, the curves were irreversiable to temperature.
4. By X-rays analysis, recrystallization spots were recognized at 200°C and that temperature was the same as that of the beginning of the second crook of curve of the thermo-electro notive force.
5. In the curve of the change of hardness, softening was noticeable at the temperature at which the crook began.
So the first crook of curve of the thermo-electro motive force was caused by the crystal recovery and the second of it was by the recrystallization. Further the temperature ranges of the recovery and the recrystallization were researched.

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