The mechanisms of corrosion and environmental
fracture of 7xxx alloys, particularly the
role of the microstructure in corrosion behavior,are strengthened by a precipitation hardening
sequence, including solution heat
treatment and quench, followed by artificial
aging. The primary precipitation sequence is
complex, with a series of Guinier-Preston (GP)
zones and metastable phases, resulting ultimately
in the equilibrium phase, M, (or Z)
(MgZn2), and/or T (Mg3Zn3Al2), depending on
composition. Copper can also be incorporated
into the precipitates
have been studied for decades and continue to
be an area of active research. An in-depth treatment
of this topic is beyond the scope of this
review section. Several thorough reviews of the
mechanisms of environmental fracture of 7xxx
aluminum alloys are available