The effect of two-step anodizing on the suppression of burning of aluminum surface during high current anodizing was investigated in oxalic acid-based electrolyte. When second anodizing at high current density was performed on aluminum coated with a first alumina layer with different thicknesses, the growth of the anodic film during the second anodizing was better with thinner first layer. On the other hand, when the same second anodizing was performed on aluminum coated with a first layer with different cell diameters, the larger cell diameter of the first layer was more effective in preventing burning. The relatively large concave arrays on aluminum formed by the first anodizing also inhibited burning during the second anodizing. In each method, it was found that prevention of burning could be achieved by dispersing pore generation sites and suppressing local current concentration during the second anodizing.

The Mg_0.1In_0.9 phase with FCC structure was formed in Mg-In and Mg-Al-In alloys. The LCR (Limiting Cold-Rolling ratio) at room temperature tended to increase with increasing area fraction of the Mg_0.1In_0.9 phase, and the LCR achieved 80% for the single Mg_0.1In_0.9 phase in both alloys. The hardness value of the Mg_0.1In_0.9 phase in the Mg-In binary alloys increased after rolling originated from grain-refinement by recrystallization and precipitation hardening due to processing heat generated by rolling at room temperature. On the other hand, the Mg_0.1In_0.9 phase formed in the Mg-Al-In ternary alloys was stable at room temperature and work hardened after rolling. Since the Mg_0.1In_0.9 phase dissolves about 5 mol% of Al, substituting Al for In in the Mg-In alloy was effective in reducing density. The density of the Mg₈₀Al₇In₁₃ (mol%) alloy is 2.60 Mg/m³, which is lower than that of Al, and the LCR showed 49%. In Mg-In alloys, the substitution of Al is effective in developing alloys that are easy to process at room temperature and have low density, because the Mg_0.1In_0.9 phase has a solid solution of Al and contributes to phase stabilization at room temperature.

Measurement of stress-strain curves under tension-compression reverse loadings is crucially important for the understanding of the Bauschinger effect of aluminum alloy sheets. Uniaxial compression of sheet metals is carried out with supporting flat plates, which clamp a specimen to prevent it from buckling. The clamp forces generate the thickness stress and the friction forces. In the present study, influence of the thickness stress and the friction force on the stress-strain curve and the validity of corrections of these effects were investigated by using the finite element analysis. It is revealed that the correction of thickness stress effect by using the equivalent stress did not work appropriately. While, subtraction of the friction force from the measured load corrected the friction effect. Furthermore, the uniaxial tension/compression experiments demonstrated the effectiveness of correction of friction effect. A rectangular window was machined on the supporting plate so as to measure the deformation of a specimen by the digital image correlation method. Analysis of the measured displacements in the window was able to detect the occurrence of wrinkling and buckling during uniaxial compression. Eventually, using the present plate-type antibuckling fixture, the stress-strain curves for several reverse loadings were successfully measured.

In recent years, joining technologies have been developed owing to multi-materials. From the viewpoint of recycling, separating the joined materials is necessary when they are disposed. Our previous study of joining steel and aluminum plates showed that easy separation by foaming the joining area at the time of disposal is effective. Still, it could not be applied to a single aluminum plate. In this study, we attempted to use the foaming agent to the joining interface before FSW of steel and aluminum plates so that it could be applied to a single aluminum plate. Thereafter, the welding surface was foamed by heating. As a result of four-point bending tests, it was found that the fracture load required to fracture the specimen can be reduced by foaming the welding surface compared with those of the nonporous specimens or only heated specimens.