퇴화 및 재시효 처리가 고강도 Al 7075합금에 미치는 영향

Abstract

The effect of the retrogression and leasing (RRA) treatment on the high strangth Al 7075 alloy was studied by measuring the hardness behavior and the propagation rate of the stress corrosion (SC) crack Transmission electron microscopy was used to investigate the variation of the microstructure of both the matrix and the grain boundary. The initial rapid decrease in the strength during the retrogression treatment is believed to be due to the partial or complete dissolution of small particles of η` transition phase. The RRA treatment results in a significant decrease of the SC crack propagation rate without deteriorating the original T6 strength of the alloy. This is believed to be due to a significant coarsening of grain boundary precipitates during the retrogression treatment. The RRA structure retains a high density of overall particles in spite of their significant coarsening.