Stress-Corrosion Cracking of High-Strength Aluminum Alloys

Transitions between pitting and intergranular corrosion in AA2024

“…Fig. 4 shows the hardness changes for AA2024 aged for different times at 190°C, which are in agreement with values reported in literature [10,12]. Hardness initially decreased during artificial aging due to partial reversion of the GP zones.…”

“…20(b). Table 2 Influence of orientation and potential scan-rate on breakdown potentials for AA2024-T3 and T8 Table 3 Breakdown potentials for various tempered AA2024 (ST) alloys in Ar deaerated 1 M NaCl at scan rate 0.1 mV s -1 The selective grain attack seen on the T8 temper is consistent with the observation of decreased susceptibility to IGC with artificial aging [22]. The change in the form of attack can be explained by a decrease in Cu content of matrix phase with aging, which makes the grain more susceptible to breakdown than the GB or SDZ.…”

“…In addition, scattered through the matrix are a lot of large and rod shaped particles containing Al, Mn, and Cu (possibly Al 20 Mn 3 Cu 2 ). There was little evidence for the existence of precipitate-free zones (PFZ) along the grain boundaries in T3 temper although the formation of PFZ adjacent to the grain boundaries during quenching has been reported [10]. However, many rod shaped precipitate particles can be seen in GB regions, Fig.…”

“…1(c)). In naturally aged AA2024-T3, it is believed that the matrix contains homogeneous coherent precipitates, denoted as GP zones, as well as fine hardening precipitates (S'Al 2 CuMg) [10,12]. Fig.…”

“…However, differences clearly exist between pitting and IGC. For example, artificial aging is thought to minimize IGC susceptibility, but may not necessarily improve pitting resistance [2,9,10]. Furthermore, the growth kinetics for IGC may be different than for pitting.…”