Ａｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ系合金の溶体化焼鈍組織の形成に及ぼす微細Ｚｒ化合物の影響

Abstract

Effects of Zr contents, purities of base aluminum metals, hot and cold working on the formation of so-called unrecrystallized grains in alloys based on AA-7050 have been examined with special reference to effect of fine particles on the migration of recrystallization front.Unrecrystallized grains in solution annealed alloys formed in the regions where fine metstable Al3Zr particles under critical sizes existed. The particles precipitated during annealing of cast ingots as well as of hot worked specimens. With increasing Zr contents, the fraction of fine particle precipitated areas increased and the size of the particles decreased. The critical radii of the particles in hot and cold worked alloys were respectively 0.018μm and 0.014 μm. With Zr contents, the fraction of unrecrystailized grains increased and the size of recrystallized grains decreased also. These results lead to the following general conclusions: The fraction of unrecrystallized grains increases with the fraction of regions where fine particles under the critical size exist. The size of recrystallized grains increases with the size of fine particle free areas. Effects of purity of the base metals as well as cold working were also interpretable with this general trend.