Age-hardened Al–1.0 mass%Mg₂Si alloy (base alloy) and Al–1.0 mass%Mg₂Si–0.46 mass%Cu alloy (0.5%Cu alloy) specimens were tensile-tested at room temperature. Localized deformation near grain boundaries in these alloy specimens were investigated by scanning tunneling microscopy (STM). The 0.5%Cu alloy specimen had intergranular fracture surface as the base alloy, although uniform elongation of the alloy was increased up to about 4% strain by copper addition. The surface topography of the “fold” in both the base and 0.5%Cu alloys were consistent with those of the Al–1.0 mass%Mg₂Si alloy with 0.36 mass% excess silicon. Direction of the grain boundary motion in the base alloy was explained by the magnitude and direction of maximum resolved shear stress on the grain boundary plane (corresponding to Fmax), but in the 0.5%Cu alloy, it was not. Frequency of fold formation in the base alloy reached to about 40% of all triple points in the gauge area, while it was about 30% in the 0.5%Cu alloy. For about 80% of the steps at grain boundaries, the height (at ε≒4%) was less than 200 nm in the 0.5%Cu alloy.

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Effect of cooling rate during casting, which is controlled by changing DC ingot thickness, on the tensile properties and formability of Al–0.6%Mg–(0.6–1.6) %Si alloys were investigated. The formability is evaluated by using deep drawing and bending tests. In case of high cooling rate corresponding to that of the roll-casting, the tensile and yield strength, local and total elongation and deep drawability are increased. The increase of tensile properties is due to a marked reduction in the size and amounts of second-phase constituent particles and an increase in the solute element concentration in the matrix. The improvement of deep drawability is related to an increase in the tensile strength. On the other hand, the bendability of the alloys cast in a high cooling rate is inferior, especially in the direction transverse to the rolling direction. These alloy ingots were not homogenized and not hot-rolled to simulate the fabrication process of a roll-cast strips. The fine second-phase particles existing continuously on cell-boundaries act as propagation routes of cracks during bending and result in poor bendability.

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Magnesium alloys are well known to have high damping capacity. However, reports on damping characteristics of magnesium alloys, especially used practically, are very limited. In this study, the effects of alloy composition and heat treatment were investigated on the damping capacity of the hot-rolled and die-cast specimens of Mg–Al alloys. In addition, stress and frequency dependencies of the damping characteristics were also evaluated. The factors, which may influence the internal friction at the low stress range in magnesium alloys, were also investigated based on the Granato-Lücke theory. The increase in maximum bending stress applied to the specimen increases the specific damping capacity. This increment at low stress range is due to the internal friction of dislocation type mechanism in magnesium alloys. It is also found that the internal friction at high stress range does not agree with the Granato-Lücke theory. Therefore, besides dislocation type mechanism, there is a possibility of additional mechanism, for example, the formation of deformation twin in these alloys. Furthermore, increases in the contents of alloying elements remarkably decrease the specific damping capacity. However, the frequency does not affect the specific damping capacity.

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The drilling performance of hyper-eutectic Al–17 mass%Si–T6 extruded alloy was examined with HSS drills to investigate the effects of drill point angles, helix angles and tip configurations on drilling forces (thrust and torque) and tool life. A series of drilling experiments were conducted by using a CNC drilling center (step less drive) with a change of cutting speed and feed rate under a wet drilling condition. The thrust force decreased with reducing the point angle of drills. However, the torque force changed little. Both forces of torque and thrust decreased with increasing the helix angle of drills, but it showed no effect on the forces when exceeded 30°. The thrust force lowered in order of cone, two rake and three rake types. The most long tool life was obtained under the cone type configuration with a point angle of 90°~100° and a helix angle of 30°~35°. Drilling forces depended strongly on the cutting speed.

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A 7475 aluminum alloy sheet was prepared by hot rolling, intermediate annealing, cold rolling and solution heat treatment followed by water quenching and final heat treatment of either annealing or natural aging. Equiaxed fine grain structure and anisotropy of the specimens were almost the same. Formability was evaluated by the Erichsen and bend tests. Higher post-uniform elongation led to better formability. Formability was associated with solute atoms and precipitates. Solute atoms localized slip deformation and promoted the formation of microbands which led to shear bands. Fine precipitates below 0.1 μm were also supposed to deteriorate the formability by preventing dislocation motion. In contrast, precipitates from 0.2 through 0.5μm in size were good for uniform deformation.

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MMC/Al laminate composites with two types of the laminate structures, where various numbers of Al₁₈B₄O_33W/ AC4CH composite layers and A1050 sheets are sandwitched, have been successfully fabricated by alternatively stacking composite layers and aluminum sheets and hot pressing. Impact properties have been evaluated as a function of laminate structures and the loading directions. The lamination yielded a remarkable improvement in the absorved impact energy compared to that of the monolithic MMC. In the case of edge wise loading, the laminate composite sandwitched by aluminum sheets had a higher impact energy than that sandwitched by MMC layers. There was further an anisotropy in the property, that is, impact values for the flat wise loading under a constant volume fraction of aluminum sheet dramatically increased with the increase in numbers of aluminum sheets, while impact values for the edge wise loading remained nearly constant.

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An investigation on vacuum distillation of magnesium was carried out to obtain high purity material for basic research use, using a Mg–20%Al electrolytic magnesium (99.93%) base alloy as a raw material. Magnesium vapor was found to be condensed at a region where the temperature ranged from 625 K to 750 K involving steep temperature rise ascribed to the latent heat of condensation. To permit the condensation to occur uniformly on the sleeve, the temperature of the condenser portion was controlled within the above range. Purified magnesium of about 3 kg was obtained from the raw material of 4 kg by a distillation for 86.4 ks at 933 K. Impurities such as Fe, Mn, Si, commonly contained in commercial magnesium, were substantially eliminated by this distillation, resulting in a purity above 99.99% that was significantly increased from that (99.93%) of electrolytic magnesium.

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High strength aluminum alloys were aged at 383 K. Their aluminum alloys were made clear to consist of two major substructures with different scale; metastable phase with a few nm size precipitated in the matrix and the quaternary rod-like intermediate phase with a few micrometer length containing Mn. The remarkable strengthening is dominantly attributed to the precipitation hardening due to fine metastable phase. In order to get further high strength, we have carried out systematic investigation using the various Al–Zn–Mg–Cu based alloys with different compositions of Zn and Mg. By a synchrotron radiation small angle scattering technique, the structure change of the alloys during isothermal aging was examined. The change of Vickers hardness during isothermal aging, could be well expressed as a function of the square root of particle size multiplied by volume fraction of metastable precipitates, suggesting the coherency strain model for the interaction of precipitate with dislocation. The coherency strain for each alloy was experimentally estimated.

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