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Corrosion behaviour of twin belt cast EN AW 7075 alloy
Author(s) -
Birol Y.,
Birol F.,
Yuksel B.,
Duygulu O.
Publication year - 2013
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201206521
Subject(s) - intergranular corrosion , metallurgy , intermetallic , materials science , alloy , corrosion , grain boundary , precipitation , pitting corrosion , solid solution , microstructure , physics , meteorology
The corrosion behaviour of the twin belt cast EN AW 7075 alloy is governed by intermetallic phases, namely Al 12 (Fe,Cr,Mn) 3 Si, Mg 2 Si and CuAl 2 , and by Mg(Zn,Cu,Al) 2 precipitates. The former are responsible for pitting activities while the Mg(Zn,Cu,Al) 2 precipitates play a key role in intergranular corrosion. The very fine dispersion of Mg(Zn,Cu,Al) 2 precipitates in samples aged to peak hardness undergo coarsening, particularly along the grain boundaries, when the hot band samples are overaged. Overageing improves the resistance to intergranular corrosion while the samples in T6 temper suffer heavy attack along grain boundaries. While ageing treatments hardly produce any change in the features of the intermetallic particles, they nevertheless seem to impact the pitting response. This may be accounted for also by the precipitation activities which in turn, change the chemistry of the solid solution matrix. Overageing to the T73 temper implies a higher purity matrix and thus changes the microgalvanic effects when exposed to neutral chloride solutions.