The high intensity 6000 based aluminum alloy and the heat treatment method null Si of being superior in resistance stress corrosion

摘要

PROBLEM TO BE SOLVED: To improve the stress corrosion cracking resistance of a 6000 series aluminum alloy while maintaining its high strength.;SOLUTION: In an Al-Mg-Si alloy or an Al-Mg-Si-Cu alloy, grain boundary precipitates are allowed to exist at intervals of ≥110 nm and also the size of the precipitates in the direction of grain boundaries is regulated to ≥70 nm. Further, such a form of precipitation can be obtained by subjecting a 6000 series aluminum alloy ingot to primary aging treatment consisting of holding at 150 to 200°C for 3 to 80 hr after solution heat treatment, then to restoration treatment consisting of heating at ≥300°C/min temperature rise rate, holding at 200 to 270°C for 0.5 to 20 min, and cooling at a rate of ≥500°C/min, and further to reaging treatment consisting of holding at 150 to 190°C for 8 to 80 hr.;COPYRIGHT: (C)2000,JPO