RRA処理による7075アルミニウム合金の応力腐食割れ性の改善
1990 年 40 巻 2 号 p. 82-87
詳細
1990 年 40 巻 2 号 p. 82-87
The RRA (retrogression and re-aging) process was investigated in order to reduce the susceptibility of 7075 aluminum alloy to stress corrosion cracking, and to keep high strength due to T6. The process includes the first low temperature aging, the second retrogression at higher temperature, and the third re-aging at low temperature. For the first aging the usual T6 treatment is practically suitable. For the second retrogression the higher the temperature is adopted and the longer the time is done, the lower the susceptibility is effected, although the strength decreases in the case of over-aging of the retrogression. For the third re-aging it is preferable to increase the temperature and the time to an extent within the permissible range of loss in strength. These effects can be explained by taking account of the different influence of the RRA process on the structure of precipitates within grains or at grain boundaries.
