This is to report on the study of the relation between the Mg/Si weight ratio and the mechanical properties or electrical conductivity of Al-Mg-Si ternary alloy.
The findings are as follows:
(1) In the case of annealed materials, the strength in the excess-magnesium region is more than that in the excess-silicon region, while in the precipitation-treated materials, the relation is completely reversed. Electrical conductivity in the excess-magnesium region is less than that in the excess-silicon region both in the cases of annealed and precipitation-treated materials. These are considered due to the effect of excess-magnesium in aluminium solid solution to the hardening of matrix and to the decrease in electrical conductivity, and the effect of excess-silicon to the increase in strength and electrical conductivity by their precipitation.
This suggests that in ternary alloy of Al-Mg-Si, there is some interaction between the precipitates of Mg₂Si and silicon, which gives rise to the increase in strength from "balanced" to "excess-silicon" alloy, since in binary alloy of Al-Si, there is only a very slight precipitation hardening effect.
(2) Regarding the relation between split aging effect and the Mg/Si content ratio, its effect is recognized on the whole region of the ternary alloy, especially in the excess-magnesium region and in the balanced Mg₂Si. Split aging effect is observed in the electrical conductivity more remarkable than in mechanical properties, and this effect decreases as the temperature gets higher and the time of aging gets longer.
The rate of aging of the materials in the excess-silicon region, especially in high temperature, is more than that in the excess-magnesium region.

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Five kinds of less-common metals; Ta, V, Y, Nb and Hf were added to the three kinds of aluminium alloys; 2S, 52S and 61S. The master alloys used were produced by arc melting process, containing 10w/o of each metal.
The workability of the three aluminium alloys was not decreased, when each of 5 less-common metal was added. These were cold-rolled by 90% reduction. High temperature strength could be enhanced by addition of up to 0.5w/o of V and Hf (Fig. 2). This effect was most remarkable in 2S, and V was the most effective element. This alloy did not show softening even after heated at 300°C for 100hrs. But, V was slightly less effective than Zr, on which the authors reported several years ago. To increase the strength, any of 5 kinds of metals was found to be effective, and V was, again, most effective.
Corrosion resistance of 52S series alloys did not deteriorated by the addition of such less-common metals. It was rather improved by the addition of Y. Y also reduced stress corrosion sensitivity im Al-Mg alloys (Fig. 3).

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The macrostructure of the following aluminium alloys were examined: Al-Ti (Ti<0.16%), Al-Mg (Mg<8.0%), Al-Mg-Ti (Mg<8.0%, Ti<0.16%), Al-Cu (Cu<8.0%), Al-Cu-Ti (Cu<8.0%, Ti<0.16%), Al-Zn (Zn<8.0%) and Al-Zn-Ti (Zn<8.0%, Ti<0.16%).
The purity of aluminium used as the basis was 99.99% and 99.5%. The specimens were prepared under different conditions: one was cast in a specially designed asbestos mould for making it solidified directionally, and another was cast in an ordinary metallic mould.
Through this experiment, the macrostructure diagrams were established as shown in Fig. 3, 4 and 5.
The findings are as follows:
The macrostructure diagram for specimens of directional solidification consists of three regions; columnar crystals, "Fiederkristall" in columnar crystals and granular crystals. In the case of using 99.5% aluminium the region of granular crystals is wider than in the case of 99.99% aluminium. Diagram for specimens of solidification in a metallic mould also consists of three regions: columnar crystals, mixture of columnar and granular crystals and granular crystals. In this case, the region of granular crystals is wider than that in the directional solidification, and "Fiederkristall" does not appear.
The angle between the direction of the tabular crystal, a member of "Fiederkristall, " and the direction of heat flow is, in most cases, less than 20°.

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This report is on the corparate study about fluxes, various kinds of degassers, grain refinement agents and modification agents for aluminium alloys (JIS-AC8A and AC8B) and is also on the control standard for gas contents in the molten alloys for permanent mold casting, which is correlative with the size of shrinkage cavity and the gas porocity.
Sixteen fluxes selected by the combination shown in Table 1 are used. And the change in gas content with the progress of flux treatment is measured by use of vacuum solidification method.
The relation between gas content and distribution of porocity is measured, through microscopic and X-ray radiographic inspections, on the finished section of a piston which has been cast by use of the permanent mold casting machine produced in the Fiat Company.
Through the above mentioned experiments, the followings are found out:
(1) The combinations of fluxes which are most effective and reliable for the refining action are:
For covering KCl+NaCl
For refinement K₂TiF₆+KCl+NaCl
For degassing Dry N₂gas.
For modification NaF+KCl+NaCl
(2) Shrincage cavity, which takes place in the skirt of piston, is tended to concentrate locally when the gas content gets lower. For dispersing the cavities, therefore, some content of gas is required.
When the gas content is above the fifth grade - the gas content grades are decided on the test pieces for vacuum solidification method - the pin holes are observed, but when the content is below the fourth grade, the pin holes can not observed through macroscopic inspection.
On the other hand, as the fluidity of molten metal is inversely proportionate to the gas content, the gas content is required to be kept below the third grade to avoid the unfilling defect.

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The micro-structure of the"hardspots by segregation"was reported in the previous paper. This is to report on the study regarding the measurement of hardness and analysis of chemical element of this kind of hardspot.
(1) The hardness of the hardspot is not so high. It is in the range of 110HV to 200HV in microvickers hardness.This hardness is classified into five groups: 110HV-130HV, 130HV-150HV, 140HV-160HV, 150HV-170HV and 170HV-200HV.
(2) The hardness of the hardspot is 1.14 to 1.67 times of that of matrix.
(3) More chemical element are contained in the hardspot than in matrix. The content of Cu is 3.7-6.5% and that of Si is 8.5-12.3%
(4) In comparison with matrix, 1.23-1.86 times of Cu, 1.10-1.46 times of Si, 0.86-1.60 times of Fe, 1.43 times of Mg and 1.09-1.27 times of Zn are contained in the hardspot.

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Cl₂, N₂ and H₂ gas are blown into molten Al for degasification. Effects to degasification is affected in order to H₂, N₂, Cl₂ by measurement of vacuum discharge extruction method. But most effective gas is considered to active Cl₂. Inactive gas (N₂, H₂) are needed refining to moisture or oxygen.
Some observations of degasification mechanism to inactive gas blowing method are presented.

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AZ63 casting alloy was molten and treated by several different processes, including flux refining, chlo-ri nation, C₂Cl₆ addition, super-heating, etc. and was cast in the green sand tension specimen moulds. By use ofth us produced specimens, tensile strength test was made on F and T₄ conditions and grain size test on T₄ condition.
Under the grain refining test on the Be-added AZ63 alloy, which was treated by "C₂Cl₆ addition, "theeffect of Be and C₂Cl₆ to the grain size was examined.

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In order to cope with recent development in making lighter the hull of high speed boat special efforts are generally being given to reduce the weight of engine outfits.
In line with this tendency the shipyard is also endeavoring to reduce the weight of exhaust pipe & muffler on torpedo-boat and hydrofoil vessel, coupled with such the parts as tank, pipe & strainer etc. & has decided to go ahead on this direction.
This is based on the result of test effected previously (aluminium alloy exhaust pipe did not show any deterioration after several ten hours testing in 12 WZ type engine) as well as of the intermediate observation of trial test of the boat "Arakaze, " ensuring the possibility of adopting light alloy for such purposes.
This report comprises therefore the test result of exhaust pipe in the light alloy boat "Arakaze" which serves as marine guard, the property of the Marine Safety Agency.
After using for 6 months at about 370°C of exhausting temperature the inside of jacket has been examined. Neither was abnormality observed under macro-inspection nor under microscope.
Also, although the region directly contacted to high temperature was found mostly sooty, no deterioration at all. But a slight unusual condition was observed around the inlet part of exhaust pipe that appeared even so slight as to make no difference to the case of iron exhaust pipe.
Consequently, should aluminium alloy pipe be solidly anodized, careful in welding & fixing, attentive to electrolytic corrosion, aluminium alloy can be used adequately as the material for exhaust pipe & mufler on practical application.

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