For heavily cold rolled 3004 aluminum alloy sheets, it is well known that partial annealing followed by light reduction rolling enhances cube texture formation during the subsequent annealing. In order to know a formation mechanism of the cube texture, especially to clarify behavior of cube-oriented grains during the intermediate processing, changes in microstructure, texture and micro-texture were precisely examined using X-ray analysis, SEM and EBSP techniques. As the results, it is concluded that preferential growth of the cube grains that have nucleated during the partial annealing brings about the strong cube texture after the final annealing. Extent of the preferential growth strongly depends upon the condition of the partial annealing. From the results of EBSP image-quality analysis, the preferential growth of the cube grains is attributed to the fact that an increase in residual strain during the light rolling for the cube grains is lesser than that for grains other than cube orientation.

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Annealing textures of 3N (35 ppm Fe) and 4N (7 ppm Fe) aluminum foils for electrolytic condenser produced by intermediate annealing-light rolling processes were examined. The aim is to clarify (1) mechanisms of difficulty of cube texture formation in 3N foils as well as in thinner foils, (2) dependence of suitable intermediate annealing temperature on iron contents, and (3) significance of intermediate thermo-mechanical treatments and effect of pre-annealing on the cube texture formation. It has been elucidated that the significance of intermediate thermo-mechanical treatments should be pursued to the following nature of the development of cube texture; the development in thin foils depends distinctly on the nucleation process and the primary recrystallization grain size distribution of cube and R components which are extensively affected by the iron content less than 0.01 mass%.

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AZ31 magnesium alloy plate, which set up a Local Tensile Strain crack tester, were welded using both DC and AC pulsed TIG welding machine. Effect of pulse frequency on crack sensitivity of welded alloy were investigated. The longitudinal cracks appeared on center of the bead which became clear the solidification crack after the observation of fractured surface using SEM. In the case of AC welding, the cracks occurred low applied load compared with DC welding. This fact is explained that the size of molten pool on the AC welded is larger than that of the DC welding. Regardless of the welding methods, occurrence of the solidification crack have a tendency to depend on the pulse frequency, and it is recognized that the solidification crack sensitivity decreases with the frequency of 30 Hz. The length of solidification cracks have a tendency to depend on the grain size on the fusion zone. This phenomenon is possibly explained by the fact that cracks did not easily propagated on the fusion zone because the applied stress is dispersed in fine grain. The solidification cracks of TIG welded AZ31 magnesium alloy were occurred by restraint stress due to the deformation during welding process and could not recognized the influence of the segregation of compounds on the fusion zone.

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Effect of hot rolling and testing temperature on superplastic characteristics of a SiC_p/6061 aluminum alloy composite made by a vortex method before squeeze casting and extrusion were investigated in order to make clear the superplastic deformation mechanism. Total rolling strain of about 94% was given to the composites in rolling temperatures from 843 K to 873 K and in the rolling strain per passes of 0.05 to 0.30. Fine grain size of about 1.6 μm was obtained in the composite rolled at temperature of 573 K and at the strain per pass of 0.10. The flow stress was not so effected by rolling strain per passes, and the composite exhibits m-value of 0.33 and the maximum total elongation of about 350% at the strain rate of 0.24 s⁻¹ and at 853 K. Total elongation of more than 100% was obtained in the wide strain rate region from 0.003 to 1.30 s⁻¹ and in rolling temperatures of 573 K, 673 K, and 723 K. Relationship between ε^1/2 and σ became linear when exponent of n = 2 was selected. Apparent activation energy determined from relationship between strain rate and effective stress (=flow stress minus threshold stress) was higher than that of lattice self diffusion of aluminum so that it is thought that high strain rate superplasticity of the composite could occur by grain boundary sliding, and grain boundary diffusion and liquid phase accommodation mechanisms. On the fracture surface of the composite after superplastic deformation, filaments and cavities in striation structures were observed and it became clear that on the microstructural level superplastic phenomena occur.

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Although many surface modification technologies had been proposed and applied to ferrous materials, a few methods can be capable to improve the surface properties of aluminum alloy castings. The present paper proposes a novel process, called friction thermomechanical process (hereafter referred as FTMP) for surface modification of AC2B aluminum alloy castings. In this process, a non-consumable rod is forced to contact the substrate under specified load while rotating. The friction heat, generated at the interface between the rod and substrate, makes substrate surface metal plasticized. The coarse cast microstructures on the substrate surface have been continuously refined due to dynamic recrystallization. As the result, surface modification of AC2B aluminum alloy castings was performed by FTMP, where the zone within 3 mm depth from surface was treated with hardness increment and refined microstructures in this experiment.

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