The super high strength Al–Zn–Mg based alloy (Mesoalite20^®) with a chemical composition of Al–9.5Zn–3Mg–1.5Cu–4Mn–0.5Zr–0.02Ag in mass% includes two type of precipitates of Q and Al₆Mn phases. The Q precipitates have a quaternary composition and fine rod-like shape, but Al₆Mn has round and irregular shape. After compaction of air-atomized powder by CIP, the Q and Al₆Mn phases precipitated in sequence during heating. By hot extrusion at 773 K, their precipitates flowed along extrusion direction and only Q precipitates aligned well, which have been known to be very effective to fiber-reinforcement. When increasing Mn content from 4 to 7 mass% with constant of 1.5 mass% Cu, the amount of Al₆Mn increased remarkably. Consequently the compressive strength and plastic elongation to fracture decreased with increasing Mn content. When increasing Cu content from 0.5 to 2.5 mass% with constant of 4 mass% Mn, on the other hand, the amount of Q phase increased and their mechanical property improved slightly with increasing Cu content. Therefore the present study has proposed a new alloy with higher Cu content, which gives higher strength than that of commercial Mesoalite 20.

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Adhesion properties in simple compression of aluminum strips are analyzed in the micro/nanometer range by employing the zeroset and power spectrum fractal analyses. An atomic force microscope (AFM) is used to estimate the fractal dimensions. It is found that the adhesion and tool and specimen surfaces have fractal structure. Various fractal dimensions obtained for the adhesion and tool and specimen surfaces are compared to each other and discussed. When the surface roughness of tool is same, the ratio of the total adhesion area depends on the fractal dimension. Though the AFM apparatus is difficult to distinguish the adhesion particles from the tool surface, the power spectrum dimension has possibility of distinguishing the adhesion particles from the tool surface. Finally, a method for computer simulation of the nanometer scale surface structure is presented, and satisfactory images are constructed.

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Hot extrusion tests for the purpose of recycling of cutting chips were carried out for AZ31B and AZ91D magnesium alloys. The tensile properties at room temperature and the surface quality of the extrusions were evaluated. Excellent mechanical properties at room temperature were obtained for an extrusion temperature of 423 K for AZ31B and for 573 K for AZ91D alloy, respectively. The tensile strength and yield strength of AZ31B cutting chip extrusion were higher than those of the extrusion from AZ31B cast billet, probably due to a grain refinement effect. However, the peculiar and wavy surface roughness almost perpendicular to the extrusion direction was formed in the extrusions from cast billet as well as in the extrusions from cutting chips of both alloys. On the extrusion surface of AZ31B alloy cutting chips, a mixed texture of basal and non-basal planes was formed. Moreover, a strong basal plane texture was observed in the layer approximately 0.4 mm from the surface. Discontinuous metal flow due to the difficulty of basal plane slip along the die exit corner with a sharp rectangular edge appeared to form the peculiar and wavy surface roughness.

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Attempts have been made to clarify the influence of citric acid on pitting corrosion of 1100 aluminum. Solution analysis and electrochemical measurements reveal that coexistence of citric acid and chloride ions will severely pitting-attack 1100 aluminum.

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Eutectically solidified portion, which should be liquid at 673 K, remained in alloys containing more than 7.8 mass% Zn. From change in area fraction of the liquid phase with Zn content, boundary composition between L+α and α regions at 673 K was estimated as about 6.7 mass% Zn. Resistivity of a specimen containing 7.8 to 8.6 mass% Zn increased with descending temperature treatment starting from 673 K and saturated at 633 K. Treatment at 613 K, the reported eutectic temperature, prolonged for 602 ks gave a nearly same saturating resistivity which suggested a maximum equilibrium solubility of Zn to Mg to be about 8.5 mass%. Details to be paid attention are described for resistivity measurement of large cross section specimens requiring a large electric current to generate enough electromotive force. When the resistance was measured in liquid nitrogen, effect of Joule heat was scarcely observed. The heating effect was clearly observed when the resistance was measured in a kerosin bath. Even in this case, the effect can be eliminated easily by extrapolation of square of current versus measured resistance plots to zero current.

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