Aging and reversion behaviors in both alloys were investigated by means of electric resistivity measurement, X-ray diffraction and high resolution electron microscopy. The resistivity-aging time curves of the alloys quenched from 520°C and aged at various temperatures showed a range in which resistivity is unchanged. The resstivity in this range increased with aging temperatures and saturated to ρ=1.55μΩ•cm at about270°C. The fact means that clusters and G. P. zones can be formed below about 270°C and that the homogeneous solid solution state can be achieved above this temperature. A trace element of Sn in the Al-4% Cu alloy reduced cluster formation and accelerated θ" precipitate formation. Heating preaged alloys at temperatures from the preaging temperature to about 270°C lead to not only disolution and growth of G. P. zones but also new formation of clusters, G. P. zones and θ' and θ" precipitates, which probably resulted in incomplete reversion. G. P. zones in the Sn-containing alloy dissolved more smoothly than in another alloys.

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Two types of low speed, unsteady, orthogonal and dry cutting tests were performed on commercially pure aluminum (1100-O) plates. One was linear unsteady cutting in which "cut depth" i.e. undeformed chip thickness is linearly increased, and the other was cutting by use of a flycutter. In the former type of cutting test, the cutting force, deformed layer and residual stress are not so affected by increase in the rate of "cut depth" but are rather affected by increase in "cut depth" with the progress of cutting. The surface is especially roughened with increase of "cut depth". While, in the latter type, the chatacteristics of cut surfaces are also affected by the "cut depth", but are not so affected by a feed per tooth. But, the hardness and roughness of the plane area in the surface formed in several rotations of a cutter increase with a feed per tooth. In any types of cutting, the residual stress measurable as the compressive stress is heavy in the cut surface and shows a maximum value probably by the burnishing effect and cutting temperature just beneath the surface. The peak height and position depend on the cutting conditions.

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Sodium was recovered by using an ammonium sulfate solution and aluminum was dissolved in water as an aluminum sulfate after the sulfatizing roasting of the leaching residue. Sodalite compounds in red mud react with ammonium sulfate to give ammonium zeolite under the condition of pressure leaching at 100°C. Ammonium zeolite reacts with ammonium bisulfate at temperatures 400° to 450°C to form double salt of an ammonium aluminum sulfate soluble in water. For the recovery of aluminum, the pressure leaching with oxygen is remarkably effective to remove iron. The leaching conditions to ensure the recoveries of sodium and aluminum exceeding 90% are; ammonium sulfate concentration 0.2mol/l, time 3hr, stirring rate 100rpm. and temperature 100°C for the sodium recovery, and oxygen pressure 5kg/cm², time 10hr, stirring rate 300rpm. and temperature 100°C for the auminum recovery.

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The alloys were rolled in the reduction ratios systematically varied. Behaviors of micro-shrinkage during rolling were correlated to tensile, fatigue, and ultrasonic properties. Little change in the mechanical properties was found in the reduction ratio up to 2, because some micro-shrinkages were still discernible in the structure. The micro-shrinkages transformed into two-dimensional defects in the reduction ratio from 2 to 4. Although the tensile properties were improved, fatigue properties were still inferior. Rolling in the reduction ratios 4 or more ensured a satisfactory repairing effect on the micro-shrinkages and good properties.

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Stress corrosion cracking tests were carried out in NaCl-AlCl₃ solution under constant load. The externally applied anodic current increased susceptivility of both solution-treated and aged 5083 alloy to stress corrosion cracking. Failure occured in the alloy 38% cold rolled with in a shorter time than in the alloy solution treated. The susceptivility of 5083 alloy is independent on the serrated flow under plastic straining. Tests on the change of electric resistivity and the time to failure due to aging of an Al-5.08%Mg binary alloy showed that the susceptivility is mainly dependent on the precipitation behavior at grain boundaries and independent on the continuous precipitation within the grains. Stress corrosion cracking of 5083 alloy is closely correlated with intergranular corrosion Grain boundaries occupied with film like β precipitates provide an effective path for cracks.

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