微細粒組織を有する７４７５系アルミニウム合金温間圧延板の材料特性

Abstract

7xxx alloy fine grained sheets produced by a warm rolling method were investigated on its micro structure and bulk properties comparing with cold rolled sheets of AA7475 alloy. The warm rolled sheets kept the fine structure less than 3 μm after solution heat treatment. This structure was recognized by EBSP measurement as a sub-grain structure with a high proportion of low-angle boundary less than 15° while the cold rolled sheets had a high proportion of high-angle boundary over 15°. It was also a unique property that the texture of the warm rolled sheets consisted mainly of the β–fiber after solution heat treatment. A cross rolling method was applied for reducing anisotropy on polarized optical micrograph and led to successful results. In addition, it was found that the {011} orientation was formed strongly by the cross rolling. The {011} orientation was kept after solution heat treatment in the warm cross rolled sheets, but the cold cross rolled sheets formed a recrystallization texture without any strong components. The strength of the warm rolled sheets aged at 120°C increased about 10% comparing with that of the cold rolled sheets. The most important result in this study was that the property of resistance to SCC of the warm rolled sheets improved considerably. The reason of the above result was probably due to intermittent precipitation at grain boundaries on the warm rolled sheets in T6 condition.