This is to report of a study on the annual-ring like structure which appears in slab of commercially pure aluminium produced by the semi-continuous casting process. This structure is seen in the central part of the slab but not in the outer part. It is recognized through interferrometer that the part of rings is dented by etching. This structure disappears when the slab is heated at 500°C for more than 48 hours or rolled down to 68.8% or more reduction. It is considered, therefore, that this does not give any influence to the rolling work in practice. On the other hand, the three dimentional variation of this part has been observed by means of repeating the polishing. From the above-mentioned study, it is considered that this annual-ring structure is formed by the nonuniformity of dcnsity of the solid solution on the condition of formation of which has been further studied.

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This is a report on the annealing of cold-rolled high-purity aluminium. The softening, recovery and recrystallization of the metal have been studied by measuring the diffracted X-ray intensity count numbr of the all Debye-scherre rings by use of G. M counter.

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In the previous report, it was stated that Si and Mg as impurities in Al-Zr alloy give some influence to the effect of Zr of increasing the recrystallization temperature of aluminium.
In this report, the same influence is discussed about Mn, Fe and Cu.
1. Mn: Mn prevents the effect of Zr on the recrystallization temperature of aluminium. Through X-ray examination, it was found out that the reason why Mn prevents the above-mentioned effect of Zr is that Mn contained in Al-Zr alloy makes an intermetallic compound Mn₂Zr.
2. Fe: Like Mg, Fe does not prevent much the effect of Zr. Since it can not be observed through X-ray examination that such small amount of Fe as an impurity in Al-Zr alloy makes any intermetallic compound, it is considered the harm by Fe is negligible. But, when Fe is added to the alloy, it decreases the solubility of Zr into aluminium and increases the precipitation at the time of solidification. It is considered, therefore, Fe itself has a nature of preventing such effect of Zr as mentioned above.
3. Cu also prevents the effect of Zr, because, it is considered, it makes an intermetallic compound Cu Zr₂in Al-Zr alloy.

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In the previous report, it is stated that the non-metallic hardspots in aluminium is considered to be made from aluminium oxide or reacted brick. The reaction between aluminium alloy and fire brick is non studied. In the experiment, a hole is made on a piece of fire brick and aluminium alloy is put in it. Then the brick is heated up to 900°C and held for 40 hours.
After reaction, the brick is cut and the section of brick and alloy is observed. And then, the hardness and weight of reacted brick and remained metal are measured.
The findings are as follows:
(1) The reaction between brick and pure aluminium and Silumin (Al-12%Si alloy) is less remarkable than that between brick and Lautal (Al-3%Cu-9%Si alloy) and Hydronalium (Al-4%Mg alloy). The reacted brick is changed in its quality.
(2) Magnesia brick shows no reaction against alloys.
(3) The reaction between carborundum brick and alloys is lower than that with alumina brick. From this, it is considered that the higher the content of Al₂O₃ in brick, the more the reaction. But, between pure aluminium and Al₂O₃90%B brick and Hydronalium and Al₂O₃B brick, the reaction is very small. These cases are considered to be exeptional.
(5) Some A bricks are not reacted in this experiment, though these have been reacted in practical use, when many hardspots have appeared in the metal.
(6) The change in weight of the brick shows the same result as obtained by the observation of the section of it. This seems to show how the reaction has been made. The change in weight of the remained metal is inverse to the degree of reaction. It is also considered to show how the reaction has been made.
(7) The hardness of the reacted brick is about 300Hv-900Hv, while that in lustered position is about 700Hv-5000Hv. The high hardness is considered to be due to SiC or Al₂O₃ elements.
(8) The hardness of remained metal is not much changed, though that of much reacted one is rather high.
(9) The hardness of slag and oxides is about 200Hv-900Hv. This is same as the hardness of non-metallic hardspots. Thus, it is considered that the slag and oxides are non-metallic.

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This is to report on a comparative study on the micro-structure and properties of Magnox powder extrusion (Mg-1%Al-0.015%Be) with 0%, 20% and 40% of Mg-0.6%Zr powder and cast-billet extrusion. The findings are as follows:
(1) The grain size of powder extrusion is finer than that of the cast billet extrusion. The addition of Mg-0.6%Zr inhibits the grain growth and, consequently, increases the strength of extrusions in the state of as-extruded as well as of annealed.
(2) The more addition of Mg-0.6%Zr, the less corrosion resistance at elevated temperature. But under the temperature of 450°C, the powder extrusion of Magnox with Mg-0.6%Zr keeps sufficient corrosion resistance.

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