Eutectic and off-eutectic Al-Al₆Mn alloys were unidirectionally solidified at solidification rates 5 to 80cm/hr under the thermal gradient approximately 40 to 60°C/cm. The alloys grow forming a coupled gowth zone which depends on the thermal gradient-solidification rate ratio. Al₆Mn forms a square pillar structure at high solidification rates, but does a blade-like structure at low rates. The solidification rate R and interphase spacing λ are expressed:
Rλⁿ = A
where, n = 2.1 for the eutectic structure. The composite modulus at stresses above the yielding strength of the aluminum matrix obeyed the rule of mixture. The modulus of Al₆Mn is 14.7 × 10³kg/mm² for aligned structures. The eutectic alloy has the tensile strength of composite 10.2kg/mm. Increase in the volume fraction of fibers leads to increase in tensile strength.

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Three types of molten metal treatments, alumina balls filtration and C₂Cl₆/degassing, C₂Cl₆/degassing, and no filtration and no degassing were tried for extrusion billets. The molten metal filtration increases the strengths of 2014, 2017, 2024, 7No 1 and 7075 extrusions. The reason is decrease in non-metallic inclusions which disturb homogeneous precipitation. Ductilities of extrusions also increase by molten metal filtration. Non-metallic inclusions act as nucleating sites for dimple cleavages.

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The Al-10%Mg alloy slabs having various thickness were hot rolled at various rolling temperatures. Electron microfractography was made on the fractured surfaces in alligatoring to examine causes of alligatoring. The fractographs were compared with those of Charpy impact specimens tested at high temperatures. There are two types of alligatoring: One is connected with hot shortness of material itself and occurs at high rolling temperatures. The other is owing to the nonuniform deformation and occurs at relatively low rolling temperatures at about 50% reduction. An effective prevention for the latter, the inserted bolt method is proposed, in which the tails of the rolling material are mechanically reinforced.

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Stress corrosion cracking and intergranular corrosion of aluminum alloy was tested in NaCl and NaCl+H₂O₂ solution under freely corroding and together with potentiostatic condition. The potentiostatic test showed that critical potential of stress corrosion cracking, E_SCC, and of intergranular corrosion. E_IGC, shifted in the less noble direction with increasing the concentration of chloride. E_SCC was noted as less noble than or nearly equal to E_IGC. In acid solution (pH3) stress corrosion cracking occurred under less noble potential than in neutral (pH6) or alkaline (pH9) solution. In the natural immersion tests, stress corrosion cracking was only observed when the noblest value of natural potential during test, En, exceeded the critical value E_SCC. Potentiostatic test at -700mV vs. SCE in solution containing 0.18g/l of chloride ion at pH6 or 9 was recommended for stress corrosion cracking test because of easier detection of cracks, beter reproducibility of results and shorter time for the test in comparison with the conventional natural immersion tests. The stress corrosion cracking of 5083 alloy in chloride solution proceeds by active pass corrosion.

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Mass spectrometric analysis of the vapor phase of PbCl₂-CdCl₂ molten salt mixture was performed as a preceeding test for measuring AlCl₃ in a molten salt system from the view point of aluminum smelting. The vapor species over CdCl₂ and PbCl₂ are Cd₂Cl₄(g) and CdCl₂(g), and PbCl₂(g) respectively. No heavier species are detected up to 970K. The heat of sublimation and the activities of PbCl₂ and CdCl₂ were measured over the whole composition range. The PbCl₂-CdCl₂ melt can be regarded as an ideal solution because of a slightly negative deviation from Raoult's law at 909K. This system is found to be different from the melts of PbCl₂ or CdCl₂ with alkali chlorides. The activity results are in good agreement with the physicochemical measurements on this system. A CdCl₂-Cd metal system was also massspectrometrically examined. The inexpensive mass-filter system will be useful for studying the molten salt systems.

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