Effect of anodizing film thickness (12-60μm) and sealing time (120-900s) on corrosion behavior of anodized diecast magnesium alloy AZ91D-F has been investigated by salt spray test (SST). X-ray diffraction, EDX and ESCA showed that anodizing film consisted mainly of Cr₂O₃, MgF₂ and NaMgF₃, and that silicon oxide was thought to deposited on the anodized surface by sealing treatment. Corrosion test showed that weight loss was independent of film thickness, but that estmated maximum corrosion depth increased and corrosion area ratio decreased with increasing anodizing film thickness. Coupling test between anodizing film and magnesium alloy showed the presence of galvanic current between them, in which anodizing film was cathode and magnesium alloy was anode. Corrosion behavior of anodized magnesium alloy in SST is discussed in terms of galvanic corrsoion model.

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Pitting attack behavior has been investigated on aluminum-magnesium alloy 5052, which is galvanically coupled with pure titanium in deaerated 0.1M AlCl₃ solution at room temperature. It is shown that relation between pitting attack factor for aluminum (f^Al_pit), which is calculated from experimental data and area ratio of 5052 aluminum alloy to titanium, is revealed by electrochemical measurements. It is found that a tendency of pitting attack increases with decrease of the anode to cathode area ratio.

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The welding state of 7475 aluminum alloy pipes formed by the four-billet extrusion method at elevated temperatures was investigated. The strength of welded parts of extruded pipes was evaluated by the expanding and flattening tests. The expandability of the extruded pipes was compared with that of seamless pipes machined from the same material. The bond strength comparable to the inherent tear strength of this alloy could be obtained. Even for the pipes of which the expanding ratio was lower than the machined ones, the flattening ratio of them exceeded largely the JIS standard for welded aluminum alloy pipes. The microstructures of the welded part on the cross-sections and the appearances of the expanded fracture surface of extruded pipes also showed that the billets were welded soundly.

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The age hardening behavior of SiC whisker reinforced Al-Li alloy which was by squeeze casting, has been investigated using Vickers micro hardness test, calorimetric technique and TEM observation. It was found that the Li concentration in the composites decreased slightly when the Al-Li melt was infiltrated into the SiC_w preform. The age hardening sequence of SiC_w/Al-Li alloy composites was essentially same as that of Al-Li matrix alloy. But the age hardening behavior of the composites was more accelerated with increasing the SiC_w volume fraction at 373K, 423K and 473K than that of the unreinforced matrix alloy. It was considered that the dislocation density increased with increasing SiC_w volume fraction because dislocations were generated due to differential thermal contraction of the matrix/SiC_w during quenching after the solution treatment. Furthermore, it is made clear that the remarkable age hardening effect in SiC_w/Al-Li composites was obtained by precipitation of very fine and high density of second phase δ' (Al₃Li)in matrix of composites.

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Deformation of cross-section of H-beam under unsymmetrical bending is analysed theoretically. The analysis is carried out by use of so called energy principle, on the assumption that the displacement at any point on the cross-section of H-beam under unsymmetrical bending includes undefined coefficients. These coefficients are determined so as to minimize the functional given by the product of stress and strain. Theoretical results coincide well with the fact that sagging deformation of inner or compression side flange is larger than that of outer or tension side flange. It is also found that the lager the strain hardening exponent, n, the larger the sagging deformation of flange and web.

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In this study, the relationships between toughness and laminated cracks were investigated on 8090 Al-Li system alloys. In 8090V notched specimens, total absorbed energy increases with decreasing temperature up to 142K, and then decreases at 77K. This phenomenon is closely associated with the change in the number of laminated cracks on the fracture surface. Absorbed energy for forming laminated cracks is greatest at 142K. Crack propagation energy, then, increases, which results in increasing total absorbed energy. Dynamic fracture toughness and the number of laminated cracks increase with decreasing temperature. The maximum dynamic fracture toughness value is obtained at 5K. Dynamic fracture toughness increases due to the increase in the number of laminated cracks. Modified microcrack toughening concept is introduced for explaining increasing toughness by laminated cracks. The calculating value of increasing ratio in fracture toughness between R. T. and 77K is in good agreement with the experimental value of increasing ratio in fracture toughness. This result suggests that the effect of stress release by laminated cracks near the crack tip is the main cause for increasing toughness of Al-Li system alloys at low temperature.

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In casting of a hypereutectic Al-Si alloy, silicon is generally known to crystallize easily as a needle or plate-like shape in the matrix, resulting in the decreased machinability as well as the decreased mechanical strength and ductility. In this work hypereutectic Al-20 mass%Si alloys were fabricated using both the conventional ingot casting and rapid solidification processes in order to investigate their fundamental aspects of machinability. In the alloy produced by the rapid solidification process (R. S. P) the average size of silicon crystals was smaller than that in the alloy produced by the conventional casting process and both the mechanical strength and hardness increased. The tool wear and surface roughness of the R. S. P. alloy were superior to those of the conventional casting process alloy. The cutting force for the R. S. P, alloy was higher than that for the conventional process alloy. The chip treatability of the conventional casting process alloy was better than that of the R. S. P. alloy in the case that no chip breakers were used.

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