Maximum in current on anodic polarization curves for Al-Cr alloys after cathodic treatment in deaerated 0.1M Na₂SO₄ solution was examined in detail. The origin of the maximum has been found to be originated from oxidation of chromium from CrAl₇ intermetallic compound into chromic hydroxide.

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Direct chill cast ingots of 3003 aluminum alloy were homogenized in the two conditions and subsequently submitted to the single pass hot rolling, and the rolled plates were held at exit temperature. The precipitation by homogenization and the structural change during the holding were investigated by means of transmission electron microscopy. Homogenization at 450°C results in fine dispersion of small α-Al(Fe, Mn) Si precipitate particles, on the contrary two step homogenization of 600°C→450°C bring about coarse dispersion of relatively larger particles. In the case of the former homogenization, subgrains form neither during rolling nor during holding, because of strong pinning of dislocations by the particles. On the other hand, the subgrain structure is formed during rolling after the two step homogenization. Moreover, recrystallization nucleates in the PFZ around the intermetallic compounds, and proceeds to the inner cast cell region. The recrystallization progresses fast in the highly deformed plate. The induced strain and the coarsely dispersed particles are considered to influence the structural changes during the hot rolling after two step homogenization.

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Intergranular fracture of an Al-1%Mg₂Si-0.4%Si-0.2%Mn alloy with various grain sizes was investigated by tensile test, optical microscopy, and scanning and transmission electron microscopy. In peak aged condition, both spacing of precipitates in the matrix and width of PFZ, as well as dimple size of intergranularly fractured surface, are almost independent of the grain size. Under the investigated aging conditions, both mean height and width of slip bands at 1% strain increase with grain size. The influence of mean slip bands width on fracture stress is, however, scarcely distinguished in this alloy.

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The behavior of Si in constituents of 1050 aluminum alloy were investigated by chemical analysis of extracted residue with phenol (phenol residue method). The constituents of the ingot are transformed from Al₆Fe to βAlFeSi and finally to stable Al₃Fe by ingot heating. Si moves to the constituents from matrix at 350-450°C then dissolves into the matrix again at higher temperatures according to the transformation. The maximum Si content in constituents are 33% of total Si at 350°C. In case of the annealing of the rolled sheet, the behavior depends on thephase of the constituents before annealing. When the constituents are unstable phase (Al₆Fe or βAlFeSi), Si moves to the constituents and therefore the amount of precipitation of elemental Si is small. However, when the constituents already transformed to the stable Al₃ Fe before annealing, the shift of Si to the constituents is small and the precipitation of the elemental Si increases.

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Corrosion rate was measured in 0.01M, 0.05M, 0.1M, 0.5M, 1.0M, and 5.0M NaCl solutions. The weight loss rate shows a maximum at the 1.0M concentration. The relation between weight loss and NaCl concentration is discussed in terms of anodic and cathodic areas which are dependent on possibility of dissolution of iron from FeAl₃ intermetallic compound.

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