Direct Chill Casting of pure aluminium has special solidification process different from the Book Mold Casting.
To acpuire the essential characteristics of Direct Chill Casting, the samples were taken from the standard slabs produced in commercial plant, and, in order of producing operation, the properties of molten metal, slab, hot rolled plate and cold rolled coil were studied systematically.
The results of the studies on the relations of producing processes and on the residual effects of the preceding operations are as follows:
1) Molten metal: Chemical composition is uniform at the holding stage.
Mechanical properties are improved by holding and degassing, but at the first stage of pouring, are dateriorated temporarily and according to stabilization of operation come back to the improved state again.
2) Slab: Macro-structure is fine and uniform except the part close to the sprue and other thin skin of the slab.
Impurities of outer layer are very high, those of the layer from 2-10mm deep are lowest and those of the part deeper than 10mm are uniform which shows the mean value of the original molten metal.
Hardness distribution is similar to that of composition.
Tensile properties and impact value are uniform.
Microstructure consists of three parts, namely, finely chilled part, slowly cooled part of columner structure, and granular, dendritic part in which “Schweb-kristall” is observed.
We can't observe the periodic sweating and dark zone in which may not be able to exist in such slab made under the special casting control as this.
3) Hot rolled plate:
Segregation of surface in longitudinal or transverse direction is not recognized, but in thickness direction it exists due to the residual effect of the slab. Impurities are high at skin and low at center.
Tensile strength in longitudinal direction is lower at central part due to the effect of different distribution of hot rolling temperature and cooling rate.
Micro-structure in thickness direction differs remarkably at skin and center.
4) Cold rolled coil: Local difference of chemical composition through the coil is neglisible. Tensile strength as rolled state is uniform in the coil, but after annealing it is lower at the center part of the coil. Grain size at center part is finer than outer part, which seems to be due to the residual effect of hot rolling condition.

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In order to examine how the contents of Fe and Si in commercial aluminium wire bars effect the conductivity and the tensile strength of the wires drawn therefrom and to obtain the best conditions for the fabrication process of wire bars, the experiment was designed by stochastical method. Then, 12 test-pieces containing 0.05% Si and 0.20% Fe were prepared and each of them was drawn into wires at various hot-rolling and process-annealing temperature, keeping the same reduction ratio.
The results of the study were as follows:
1. For electric conductivity, at the 1% level, significant are Si content, hot-rolling temperature, process-annealing temperature and the interactions between Si and Fe content, Si content and hot-rolling temperature, Si content and process-annealing temperature, Fe content and hot-roiling temperature, and hot-rolling temperature and process-annealing temperature.
For tensile strength, at the 1% level, significant are Si content, Fe content, hot-rolling temperature, process-annealing temperature and the interactions between Si content and hot-rolling temperature, Si content and process-annealing temperature, Fe content and hot-rolling temperature, Fe content and process-annealing temperature, and hot-rolling temperature and process-annealing temperature.
These relations are shown in Fig. 13-Fig. 18.
2. The best conditions for the fabricating process of wire bars are, in the case of containing 0.05% Si, to hot-roll at 450°C and anneal at 310°C regardless of the contents of Fe and, in the case of containing 0.07% Si, to hot-roll at 400°C and anneal at 340°C regardless of the content of Fe.
Further, in the case of containing 0.09% Si, it is preferable to hot-roll at 450°C regardless of the content of Fe and to anneal at some higher temperature in accordance with the increase of the Fe content, so far as the tensile strength exceeds the standard value, i. e. 18kg/mm².

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This report deals with the investigations of the relations between mechanical properties and grain sizes, as well as the grain size control of aluminium sheets.
The factors influencing upon the grain size are also studied in accordance with the order of manufacturing processes.

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This paper concerns the effect of calcium added to high purity aluminium and commercially pure aluminium sheets, and the rolling behavior and recrystallization of the alloys are studied.
The rolled alloy sheets of 0-2% Calcium added to 99.99, 99.9, 99.7, and 99.5% aluminium virgin ingot, and 99.3% aluminium scrap are examined concerning macro and micro structure, edge-cracking, hardening by reduction, and mechanical properties at elevated temperatures.
The strength of aluminium alloy sheets increases with the addition of calcium, the effect of which, however, is less remarkable than those of iron and silicon. On the other hand, the ductility decreases and its effect is more remarkable than those of iron and silicon.
The macro structure of the alloy tends to become finer, and the micro-structure to blockade the branches of dendritic structure and to become granular, which is considered to be the characteristic influence of calcium on the alloy.
In the case of high purity aluminium, a small and commercially neglegible drop of recrystallization temperature is observed, but in the case of commercially pure aluminium, little change of recrystallization temperature can be observed.

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The wrought aluminium alloys currently used can be classified into two main groups; age-hardenable alloys and the alloys hardened by cold working. The strength of the former, however, will be greatly reduced by overaging which takes place above 200°C. The latter, too, will lose its strength at high temperatures due to softening caused by recrystallization, but there would be the possibility to bring the latter to be stronger than the former at the higher temperatures if the effect of cold working should be retained up to the temperature by means of preventing recrystallization by the addition of a suitable alloying element.
From this point of view, the alloying element has been searched for by the author which can enhance the recrystallization temperature of aluminium.
As it was timely discovered by Dr. M. Yanagisawa that the small addition of zirconium can raise its recrystallization temperature higher than 400°C, a series of experiments has been carried out to observe the softening behaviers of various aluminium alloys with 0.5% Zr at high temperatures.
The results obtained with Al-3%Mg, Al-1.2%Mn, Al-4%Cu and Al-6%Zn-2%Mg alloys has been reported here from among the experimental data hitherto obtained.
The softening behaviors due to annealing for an hour at the respective temperatures have been shown in Figs. 1-8 and the changes of Vickers hardness during heating at the respective temperatures after cold rolling of 50 or 75% have been illustrated in Figs. 9-12 for Al-Mg and Al-Mn alloys. Vickers hardness values have been tabulated in Table. 1, measured at room temperature for the four alloys held for an hour at the respective temperatures, followed by quenching.
As the results, Al-3% Mg alloy added with 0.5% Zr has been found to be the best, which retained its Vickers hardness of about 90 even after 100 hours at 400°C, and Al-Zn-Mg-Zr Alloy follows. Zirconium, however, has been found to have no effect its Al-Mn alloy system.
Addition of zirconium has been carried out by using the master alloy of Al-10%Zr prepared by powder metallurgy from zirconium powder containing hafnium and aluminium powder. The loss of zirconium has been found to be scarce; only 1-5% except in the case of Al-Mn system. The procedure has also the advantage to utilize low grade zirconium sponge, zirconium scrap as well as zirconium powder.
Though creep test above 300°C will be necessary before conclusion, extensive use of aluminium alloys can be expected in the field of the structural materials for supersonic aircraft as well as for nuclear reactors, if heat resistance can be enhanced through the study.

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When we wanted to produce a transparent silver anodic oxide film by sulphuric acid anodizing process, we have frequently encountered with the fact that the oxide film has happened to have yellowish brown color. Having examined this coloring-defect, we found that it was caused by the precipitation of fine particles out of the supersaturated silicon in commercially pure aluminium sheets when they were annealed at 300-400°C.
Then, we investigated the behavior of silicon in the alloy of highly pure aluminium and silicon in order to eliminate the effects of other impurities. (See Tables 1 and 2). These specimens were annealed at 300, 350, 400, 450, 500, and 550°C and analysed.
As the results, the content of the precipitated silicon reached their maximum in the annealed specimens at 300-350°C and the amount of fine particles of the precipitated silicon also reached maximum in the same specimens. (See Fig. 1 and Fig. 3). The color of anodic oxide film of the same specimens was also yellowish brown. (See Table. 3).
As shown in Table. 4, the coloring range of anodic oxide film corresponds to the range of the precipitation of fine silicon particles. Therefore, the coloring-defect of anodic oxide film is eliminated by annealing the aluminium sheets at the temperature above the solidus line corresponding to their silicon content.
The effects of the total content of precipitated silicon on the properties of aluminium sheet are shown in Figs. 5-9. Among these properties, the corrosion resistance only was appearently influenced by the size of precipitated silicon particles. (See Fig. 6).

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Few researches have been published on variation of properties of Al-Mg alloy with lapse of time of aging at 50-70°C. Otto Dahl and Klaus Detert recently published a very interesting paper relating to the problem.
In this paper, it is found that any marked variation of mechanical and physical properties such as hardness, electrical resistance, lattice constants, etc. could not be seen, when aged at at room temperature or thereabout. As the cause of these phenomena, the contiguity of atomic number of aluminium and magnesium are suggested (13 and 12 respectively).
The authors also treated this problem:
Alloy specimen were prepared by alloying four nine aluminum with magnesium and mischmetal, the composition of the first series being 2.5, 3.5, 5, 7, 10 and 12% of Mg, and of the second series 5, 7, 10 and 12% Mg with 0.3 and 0.5% of mischmetal. The small specimen of sheets, 1.2mm thick, were solution treated at 400°C, for 2 hours, then quenched in the water (1°C) and then aged at 50, 80 and 100°C for about 3, 000 hours.
During aging, hardness, microstructure, electrical resistance and corrosion resistance were intermittently tested. The corrosion resistance was tested by Mylius method; the specimen was immersed in 10% HCl water solution and the amounts of evolved hydrogen were measured.
As the results of the study, a marked variation of corrosion resistance was found. When corrosion resistance is represented by “Reaction Number” (RN), or quantity of hydrogen evolved per unit area and per unit time, its variation is shown in Fig. 6 and 7.
In other words, RN is smallest at as quenched condition, then rapidly increasses with the lapse of aging time and after passing through the maximum, it decreases on the contrary.
Corresponding to the variation of RN the hardness curve has also its inflexion point near the aging time of the maximum RN.
These changes probably suggest a formation of some special arrangement of magnesium atoms among aluminium space lattice or of an arrangement similar to Guinier-Preston Zone.

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It is generally considered that, although greater forces are required to squeeze several extrusions by the same reduction percentage, from a big billet, than to squeeze single extrusion from the billet, the pressure per unit area of the surface of the extrusion is smaller in the case of the multi-hole die than that of the single-hole die.
However, when the big billet tends to have segregation in it or larger grain-structure in the center part, it is better to use the single-hole die or to make the billet smaller, than to use the single big billet by the multi-hole die.
From the above point of view the authors made a series of experiments to investigate mechanical properties of the various extrusions by multi and single-hole dies.
Billets of pure Pb and 99.80% aluminium, 30mm dia. 40mm long as cast, were extruded by the same reduction percentage, at various temperatures, and through multi-and single-hole dies, and the different effects of two kinds of dies on extrusion pressure, flow of extrusions, and their hardnesses, as well as the effects of annealing of the extrusions on softenings and electrical resistances, were investigated.
The results obtained are as follows:
1. Extrusion pressure and hardness of the extrusion by multi-hole die are generally higher than those by single-hole and the difference becomes larger in the case of extrusion at lower temperatures.
2. Observing the flows of the extrusions, in the case of extrution at high temperature they are about the same by both dies, but in the case of extrusion at low temperature, the extrusions by multi-hole die are affected (deteriorated) by the end part of the billet.
3. The hardness of the extrusions by multi-hole die is generally high, however, in order to obtain the extrusions of uniform hardness, it is prerequisite to keep the proper extrusion temperature and suitable setting of the positions of outer holes of the die.
4. Softenings and changes in electrical resistance of the extrusion due to annealing resemble to those of cold worked metals.

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Effects of phosphor and sodium added to the aluminium-silicon alloys containing 8-20% of silicon on the mechanical properties and microstructures of the alloys are studied.
Mechanical properties are shown in Table. 2, and microstructures are shown in Photoes. 1-16. Effects of phosphor and sodium on tensile strength and elongation are shown in Fig. 1, and those on Rockwell hardness are shown in Fig. 2. Microscopic diameters of primary silicon in permanent-mold test pieces shown in Fig. 3.
The results of the experiments are summarized as follows:
(1) In normal alloy the tensile strength falls remarkably when silicon content exceeds over 14% and the primary silicon grows large.
(2) With the addition of sodium, excellent mechanical properties and fine structure are obtained when silicon content is less than 14%, but when it exceeds over 16%, the tensile strength falls suddenly because of large grbular primary silicon.
(3) With the addition of phosphor, mechanical properties are a little higher than normal alloy when silicon content is less than 14%, but they do not fall so remarkably as the normal alloy even when silicon content exceeds over 16%. For mechanical properties and microstructures of aluminium-silicon alloys containing over 18% of silicon, the addition of phosphor is more desirable than the addition of sodium.
For high silicon alloys the results of the experiment coincide with those of C. Mascré, but the variation of microstructure by the addition of sodium is otherwise explained by the authors as “diffusion theory” for the modification of silicon. According to the author's experiment, diffusion constant of silicon in liquid aluminium-silicon alloy with the addition of sodium is about 15% at 607°C, and 57% at 680°C, which is different from that of the normal alloy. By the author's “diffusion theory”, the growth of the primary silicon which has not yet been explained by other modification theories, the globulation of primary silicon and refinement of eutectic silicon are completely explained.

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The Al-Mg casting alloy is very susceptible to the content of impurities; iron deteriorates its corrosion-resistivity and silicon lowers its mechanical properties, especially ductility. These impurities come not only from alloying ingots but also from crucible and utensils for melting.
In our experiments Al-Mg alloys were kept in steel, cast iron, or graphite crucible at constant temperature for several hours, and Fe or Si contents were determined about the samples poured out of the melt from time to time, and also the sections of crucible wall were microscopically examined.
The results obtained were as follows:
1. Al-Mg alloy attacks the ferrous crucible more rapidly than aluminum or silicon, and the quantity of dissolved iron seems to become constant after a few hours.
2. Any distinct difference in iron increase is not found between the two cases of steel and cast iron crucibles.
3. The difference has little to do with the holding temperature, too.
4. Al-Mg alloys react with SiO₂ in graphite crucible, reduce it to Si and form Mg₂Si in them.
5. Al-10%Mg Alloy has more active reaction on graphite crucible than Al 4.5% Mg alloy.
6. The higher the holding temperature, the more becomes the rate of reaction.
From these result it is found that some suitable lining to the crucible for melting Al-Mg alloys is essential, and also that melting at higher temperature is not desirable because of its bad effect upon the properties of the alloys.

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This report deals with the studies on stress corrosion of argon welded ANP (Al-4% Mg-0.5% Mn-0.2% Cr) plates dipped in the brine and aqueous solution of 3% NaCl+0.1% H₂O₂.
The stress corrosion cracking does not occur in any case. The electrode potentials of deposited zone measured in the aqueous solution of 3% NaCl+0.1% H₂O₂ are more noble than those of mother plates.
Corrosion of the mother plates occurs especially on the heat affected zone, but very little on the deposited one.
Corrosion of the heat affected zone of the plates in the case of oxyacetylene gas welding is more remarkable than that in the case of argon welding (Heriarc, Sigma).

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This experiment is carried out with the object of making a heat exchanger by furnace brazing method. The materials used for joining are 99.99% Al, 99.7% Al, 1S, 2S, 3S, Al-0.5% Mg, and 52S sheets, a brazing sheet, and heat-treatable alloy 61S, and 63S sheets rolled to the thickness of 0.6-1mm. The brazing sheet consists of a core of 3S with cladded 45S. The filler materials are 43S, 45S, 718, 716, and Al-Zn-Cu alloys and the fluxes are Nasu No. 21 and No. 45.
The tensile tests are applied to the lap-jointed specimens made mainly by furnace process. Corrosion resistance tests are experimented by dipping the specimens in 5% NaCl solution. The effects are measured by the decreases of tensile strength.
The types of fracture of the tested specimens are classified into 4 groups. The results of the experiments are shown in Table. 7, Table. 8, and Fig. 9.

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The effects of cold rolling reduction and purity on the fatigue properties of commercially pure Titanium sheets were studied on Schenck's vibrating sheet bending machine. Internal heating phenomenon and corrosion-fatigue prorerties of rotating-beam specimen were studied on Ono's rotary bending machine.
Following results were obtained:
(1) The fatigue ratio (fatigue limit to nominal tensile strength) ranges from 58 to 66 per cent for annealed sheets and from 45 to 51 per cent for 50 per cent cold rolled sheets. These ratios decrease with cold rolling reduction.
(2) Fatigue limits are affected by the purity.
(3) Relations between fatigue limit and tensile strength are summarized in Fig. 5.
(4) Internal heating phenomenon is observed on unnotched rotating-beam fatigue specimens tested above the fatigue limit, but not observed on notched specimens.
(5) Corrosion-fatigue properties are excellent both in water and in 3% NaCl aq. solution.
(6) Since these liquids behave as a coolant to internal heating phenomenon, fatigue limit increases 6kg/mm² than that of in air.

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