アルミニウムの立方体方位粒の成長に及ぼす圧延傷の影響

概要

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Straight grain boundaries which coincide partially with rolling marks were observed on the surface of annealed high purity aluminum and A6061 aluminum alloy sheet under polarized light after direct anodic oxidation treatment without electro polishing. Straight traces in high purity aluminum were frequently faceted which suggests that migration of grain boundary perpendicular to rolling direction was retarded on the surface. Retardation of boundary migration was ascribed to pinning effects of oxide particles accumulated in convex part of ridges extending parallel to rolling marks. In high purity aluminum, straight boundaries between cube oriented grains were also observed with faint contrast. Annealing after removing of the surface layer by electro polishing resulted in the development of sharp cube texture with equiaxied grains by grain growth. In A6061 alloy, preferential nucleation of Mg2Si precipitates were observed at both the rolling marks and surface grain boundaries during cooling after annealing, which is explained by the fact that in the ridges in rolling marks dislocation density is high even after heat treatment at high temperature and oxide particles are accumulated.
2009-03-31