Aluminum alloy sheets containing 0.26 mass%Zr were rolled up to 96% at 400°C just below the recrystallization temperature to examine formation of the (44 11) [11 11 8] component. (111) pole figure of an alloy sheet rolled to 96% at room temperature is quite similar to that of a heavily rolled pure aluminum sheet. (111) pole figure of a sheet rolled 84% at 400°C consists of the (44 11) [11 11 8] orientation and that rolled 96% is rather well accounted for by the orientation spread from (44 11) [11 11 8] to (011) [211] than that from (112) [111] to (011) [211]. Assuming that the resolved shear stresses in operating slip systems at stable orientations are equal to each other and highest, the compressive stress axis in the (44 11) [11 11 8] oriented grains might incline 8° from the rolling plane normal. The inclination of the stress axis at warm rolling is attributed to the constraints due to macroscopically the force acting between rolls and sheets.

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An “I-Beam hot tearing test” and a solidification contraction test were carried out on Al-4.5%Cu and Al-4.5%Cu-5%Si alloys containing various additives to control the solidification structure. Al-4.5%Cu alloys containing Ti, Mg and Si have improved resistance to hot tearing. Al-4.5%Cu and Al-4.5%Cu-5%Si alloys containing Sn, Zn, Fe and Ni have poor resistance. A solidification temperature range or a brittle temperature range is not always a determinant of susceptibility to hot tearing in the alloys containing additives and including ternary eutectics. The solidifying eutectic plays an important role in hot tearing. When the grain size is refined and the dendrite arm spacing is enlarged in the alloys, the resistance to hot tearing is strengthened. Hot tearing is qualititatively explainable by interdendritic fluid flow, solid forming process and mechanical properties of growing solid.

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Three 7000 type Al-Zn-Mg-Cu alloys were artificially and isothermally aged at 393 K. A small-angle X-ray scattering technique was applied. Size, interparticle distance and volume fraction of precipitated metastable phase increase with prolonged aging time, but the difference of electron density inside and outside the precipitates remains constant. The precipitates has chemical composition similar to that of η' phase. The yield strength is strongly correlated with the structure of fine metastable precipitates. If the precipitates are 2 nm or less in average radius, the cut-through mechanism dominates the interaction of dislocations with precipitates. When the precipitates grow in size, the yield stress is mainly governed by the Orowan mechanism. The observed values are quantitatively explained by the Hirsch and Humphreys' theory.

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Practical aluminum die castings often include a number of scattered structures caused by destruction of solidified layers in a metal sleeve at a shot. The scattered structure-normal structure interface has tensile strength as low as 9 kg/mm². The scattered structure lowers the strength of practical aluminum die castings and often causes defects of pressure leakage near the gate. The quantity of scattered structures are affected by solidification behaviors of molten metal in a metal sleeve at a shot. This quantity is estimated from the heat capacity of molten metal per unit area in the metal sleeve calculated by using die casting conditions.

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A dipping test in tap water at room temperature and electrochemical measurements in 3% NaCl solution at 25°C were carried out on aluminum containing Cu up to 0.026 and Fe up to 0.45%. Filiform corrosion occurs only on aluminum containing Fe of an impurity. Polarization curves show that H₂ over-voltage and corrosion current of Al-Fe alloys are lower than those of Al-Cu and Al-Fe-Cu alloys. Anodic polarization curves on aluminum containing Cu trace and Fe 0.46% show that the current is caused by filiform corrosion and pitting corrosion. Anodic current in the potential region near the rest potential is caused by filiform corrosion. An increase in anodic current at a succeeding stage is caused by pitting corrosion.

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