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Al—Zn—Mg—Cu 系(7000系)高强度铝合金广泛应用于飞行器结构。经常选用这类合金的原因是由于它们可因沉淀硬化而获得高强度。一般来说,最好是将这类合金时效到接近于其最高强度,这种合金状态用 T6来表示。但是在这种状态下,合金的应力腐蚀断裂抗力较低。此合金的应力腐蚀断裂抗力可以通过过时效到其 T73状态而提高,但与此同时却使其强度大约降低10～15%。在1974年发现了一种称为逆转变和再时效(Retrogression and reaging)(RRA)的热处
Al-Zn-Mg-Cu series (7000 series) high-strength aluminum alloy is widely used in aircraft structures. The reason why such alloys are often used is because they give high strength due to precipitation hardening. In general, it is best to age such alloys to near their maximum strength, this alloy state is expressed by T6. However, in this state, the stress corrosion cracking resistance of the alloy is low. The stress corrosion cracking resistance of this alloy can be increased by aging to its T73 state, but at the same time its strength is reduced by about 10-15%. In 1974, a heat known as Retrogression and Reaging (RRA) was discovered