再結晶粒組織を有するAl-Zn-Mg-Cu系合金の結晶粒成長と耐応力腐食割れ特性( 材料・構造の衝撃問題)

The stress corrosion cracking, SCC, resistance of recrystallized Al-Zn-Mg-Cu system alloys having various grain size was discussed on the basis of SCC tests of the relationship between SCC failure time and average grain size, ds, in 3.5% NaCl solution, fractography, then microscopic- and X-ray observations of the recrystallized structure formation. The main results obtained in this work are as follows : (1) SCC resistance in the present 7475 aluminum alloy depended on the behavior of the grain growth. Time to SCC failure reached a peak at ds=24.1 μm, when ds> or ds direction was peculiar to an aluminum alloy start at ds=24.1 μm. Therefore, SCC resistance in this alloy has been found to be related to the secondary recrystallization behavior.