The mechanical properties of a new P/M aluminum alloy were investigated by means of hardness test, tensile test and rotated bending fatigue test. As a result, compared to the conventional 2618 aluminum alloy strengthened by heat treatment, this material, Al–7.5mass%Mg–2.5mass%Fe–0.6mass%Zr–0.2mass%Ti–1.1mass%Co–0.8mass%Mo–0.5mass%Cu alloy, has higher thermal stability because of the strengthening in hot extrusion. The tensile strength and fatigue strength at 10⁷ cycles are 690 MPa and 280 MPa respectively. The ratio of fatigue strength to tensile strength is 0.4, which is higher than that of the conventional aluminum alloys strengthened by the dispersion of incoherent precipitation particles. These good properties are presumably due to the dispersion strengthening by the fine particles precipitated in heating and straining during extrusion.

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Recently, porous aluminum has attracted special interest as a new functional material. However, the application of porous aluminum remains limited due to high-cost fabrication and low productivity. To overcome these problems, the authors proposed a new fabrication method called the “FSP (Friction Stir Processing) route precursor method”. In this study, using aluminum alloy die casting ADC12 as the starting material, porous aluminum is fabricated by the FSP route precursor method. At first, the pore structures of ADC12 porous aluminum are observed through X-ray CT. It is shown that, in the porous aluminum by FSP precursor method, the pore size distribution and the circularity of pores are similar to those in commercially available porous aluminum. Moreover, the compression tests for ADC12 porous aluminum and commercially available porous aluminum are carried out. It is shown that ADC12 porous aluminum indicates brittle fracture, and high plateau stress and high absorption energy comparing those of commercially available porous aluminum.

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The effects of the amount of the Al₂Ca(Mg) compound on heat resistance and castability of the Mg–Al₂Ca(Mg) quasi-binary alloys, the composition ratio of aluminum and calcium of which was 2 : 1, were investigated. The heat resistance of the Mg–Al₂Ca(Mg) quasi-binary alloys was improved by the covering of α-Mg grain boundaries with the Al₂Ca(Mg) compound, and more improved by increasing of the amount of the Al₂Ca(Mg) compound. The Mg–Al₂Ca(Mg) quasi-binary alloys, the compositions of which were close to eutectic one, showed the alloy solidification of the skin-formation type. The duration of the transferred pressure of those molten alloys was long, and the alloys showed the high transfer ability of alloy solidification. It improved the heat resistance and the castability of the Mg–Al₂Ca(Mg) quasi-binary alloys for the compositions of aluminum and calcium to be closer to eutectic.

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The effect of high-frequency switching electrolysis on the film thickness uniformity of an anodic oxide film formed on Al–Si (AC8A) alloy was studied. The film thickness uniformity was successfully improved by applying high-frequency switching electrolysis with positive and negative voltage cycles and not by direct current anodizing. To attain uniform film growth on an Al–Si substrate with substantial dispersion of crystallized Si particles, the effects of the applied time T_a at a positive voltage as well as of the shape of current waves on film morphology and film thickness uniformity was investigated. When T_a was set close to the time at which the current peak, T_p was observed, the most uniform film growth was achieved. This was explained by the capsulation of Si particles by intermittent oxide growth accompanied by switching electrolysis with appropriate applied intervals. The mechanism of uniform film growth was further interpreted using equivalent circuit models.

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The microstructures and corrosion resistance of the anodic oxide films formed on AZ31B magnesium alloy by anodizing under continuous sparking in alkaline phosphate electrolyte (Na₃PO₄) were investigated. Basically, voltage-current characteristic of AZ31B in Na₃PO₄ solution was the same to that obtained in other sodium salt electrolytes such as Na₂SiO₃ and NaAlO₂. However, the anodic films formed in Na₃PO₄ solution exhibited the higher corrosion resistance than that of the films formed in other electrolytes because of the incorporation of substantial amount of magnesium phosphate. The microstructures (e.g., diameter and number of pores) of the anodic films formed under sparking accompanied by current or voltage oscillation and gas evolution were strongly affected by the degree of sparking such as size, number, and appearance frequency, not by the formation voltage itself. X-Ray diffraction analysis revealed the incorporation of crystalline Mg₃(PO₄)₂ into the anodic film formed under the sparking condition of dielectric breakdown.

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