Intergranular corrosion of AA6082 Al–Mg–Si alloy extrusion: The influence of trace Cu and grain boundary misorientation

Electron microscopy analysis of grain boundaries and intergranular corrosion in aged Al-Mg-Si alloy doped with 0.05 wt% Cu

“…3). The latter observation is significant as no Cu film was previously found in the AA6082-T6 alloy with 0.06 wt% Cu investigated by Zhang et al [8,9]. The presence of the Cu-rich film and particles along such HABs can be attributed to high GB energies promoting segregation of alloying elements.…”

“…On the other hand, an Al-Mg-Si alloy (AA6082-T6) with 0.06 wt% Cu studied by Zhang et al [8] demonstrated pronounced IGC in the recrystallized microstructure when aging was performed after water quenching. High frequencies of corroded boundaries were also observed in the deformed microstructure of this alloy [9]. Apparently, concentrations in the range 0.03 wt% < f Cu < 0.06 wt% are critical for defining whether an alloy is susceptible to IGC.…”

“…Although no statistical analysis of different types of precipitates along LABs can be provided in this work because of the low frequency of LABs in the recrystallized layer, the fraction of LABs containing particles in the present material is expected to be small. For example, only less than 10% of all LABs were found to be decorated with particles in the AA6082-T6 alloy with 0.06 wt% Cu [9]. It is also indicative that the percentage of corroded LABs is lower than that of any other boundary type even in the most corroded sample exposed to the test solution for 72 h (see Table 3).…”

“…It should be noted that the previous studies of correlations between the GB type and the extent of IGC in the Al-Mg-Si alloys were mostly conducted on samples with fairly high Cu-contents (≥ 0.1 wt%). To our knowledge, only one study of such correlations was performed on the AA6082-T6 alloy with 0.06 wt% Cu, where an apparently deformed microstructure with a high frequency of LABs (~65 %) was investigated [9]. However, the surface of hot-rolled or extruded Al-Mg-Si plates and profiles is usually recrystallized [1,13,17] with a high frequency of HABs rather than LABs.…”

Broadening the design space of engineering materials through “additive grain boundary engineering”

“…However, there are other types of GBs which could improve the properties of polycrystalline solids. For instance, some recent studies pinpointed the beneficial effects of low-angle GBs on intergranular corrosion of aluminum alloys [83][84][85] and on the strength of stainless steel [86,87]. The possibility offered by AM to control the crystallographic texture and local crystallographic misorientation [41] in the build opens the path to tailoring the occurrence of different types of GBs to improve the properties of any material.…”