Grain refinement of aluminum, Al-Cu and Al-Zn alloys was examined by applying direct vibration in an alternative electromagnetic field. The grain refinement effect was roughly proportional to the current intensity, i.e. the vibration amplitude; it was most appreciable in pure aluminum and not pronounced in alloys either titanium-treated or containing a higher amount of an alloying element. One of the merits of this method was a remarkable decrease of microporosities compared with mechanical vibration. However, the segregation of a solute element near the interface of precipitates was not eliminated by electromagnetic vibration. The mechanism of grain refinement by this method is not clear, but may be explained by the accelerated nucleation effect and by detachment of dendrite tips due to thermal fluctuations.

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The effect of hydraulic pressure applied during solidification on the mechanical properties of hypereutectic Al-Si alloys (15-21wt%Si) was studied. The results obtained are as follows:
(1) The eutectic structure of unmodified hypereutectic Al-Si alloys were refined by the pressure applied during solidification.
(2) The mechanical properties were improved with an increase of the applied pressure, and an appreciable improvement was attained at above 20kg/mm².
(3) An ingot almost free from the casting defects was obtained by applying a pressure above 20kg/mm².
(4) The mechanical properties of the ingot solidified under the hydraulic pressure were not lower than those case with the treatment of modification.
(5) Dimple markings were observed on both the tensile and impact fractured surfaces.

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This study was made to investigate the formation of bleed bands in D. C. cast billets. the 99.9% aluminium billets, 13cm in diameter, were D. C. cast. By controlling casting conditions, billets with and without bleed bands were produced. Using thermocouples inserted in the mold wall, the temperature was recorded during D. C. casting. At the end of casting, a small amount of ¹⁹⁸Au was added to the molten metal and then sump contours were observed by means of macro-and micro-autoradiography. Distribution of impurities such as iron and silicon was determined by X-ray microanalysis.
The results obtained are summarized as follows:
(1) In the billets with bleed bands, the base of ingot shell was remelted and in an extreme case, molten metal exuded on to the ingot surface, as proposed by Siebel et al1).
(2) Remelting proceeded preferentially along grain boundaries where melting point was low due to segregation of iron.
(3) Bleed bands likely to be formed by the Collins' mechanism2). were not observed.
(4) By the remelting mechanism, the effects of the casting speed and the mold taper on bleed bands could be qualitatively explained.

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This investigation was performed to study the orientation dependence of the stress corrosion sensitivity and the influence of the rolling reduction in 7075-T6 alloy thick plates. The results obtained are as follows:
(1) The orientation dependence of the stress corrosion sensitivity of 7075-T6 thick plates was influenced significantly by the stress component acting in the short transverse direction.
(2) Within the rolling reduction by which the specimen was not recrystallized, the stress corrosion resistance in the short transverse direction was improved with an increase of the rolling reduction.
(3) In regard to the stress corrosion sensitivity of the plate surfaces, the unrecrystallized structure obtained by less than 92%reduction was relatively insensitive, while the recrystallized structure was sensitive.
These results show that grain boundaries, especially those lying perpendicular to the stressing direction play an important role in the stress corrosion sensitivity of 7075 alloy.

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A study was made of the anisotropy in the tensile properties of 5083-0 aluminum alloy plates of thickness 22 and 80mm. Specimens with round and rectangular cross sections were prepared in the longitudinal (L), long transverse (LT) and short transverse (ST) directions. The principal results obtained are as follows.
(A) Results for 22mm thick plates: (1) Approximately same tensile strength, σ_B, was obtained in both the L and LT directions, but specimens with a round cross section showed slightly higher σ_B than those with a rectangular cross section. (2) Specimens in the LT direction showed appreciably lower 0.2% proof stress, σ_0.2, than those in the L direction. (3) Round specimens in the L direction displayed consistently lower elongation, δ, but almost the same value of δ was obtained for rectangular ones in the L and LT directions and round ones in the LT direction.
(B) Results for 80mm thick plates: (4) Changes in the tensile properties were observed with the location in the thickness direction when the specimens were tested in the L direction. The specimens taken from the outer layer showed slightly lower σ_B and σ_0.2 and slightly higher δ than those from the center. (5) The values of σ_B, σ_0.2 and δ did not change with the location in the thickness direction when tested in the LT direction. (6) The mean values of σ_0.2 and δ for the round specimens in the L direction taken from four different locations in the thickness direction were virtually identical with those for the large specimens of 80mm thickness. (7) Specimens in the ST direction showed considerably low δ while they showed approximately the same σ_B and σ_0.2 as those in the LT direction.

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