The effects of Mg and Ag contents on the corrosion resistance of Al-Cu-Mg-Ag alloy were investigated by intergranular corrosion (IGC) testing. The corrosion mechanism of the alloys with different chemical composition was discussed by transmission electron microscopy (TEM) and electrochemical analyses. The results indicate with increasing Mg and Ag content, the age hardening rate of the alloy increases. The size of the strengthening phases Ω decreases with increasing Mg content whereas phase volume fraction increases. More solution atoms are consumed to form the precipitation on the grain boundaries of the alloy with higher Mg content, which increases the potential difference between precipitation free zone (PFZ) and the matrix and subsequently, the IGC resistance of Al-Cu-Mg-Ag alloy decreases. Increasing the Ag content, the main strengthening phases transform from great amounts of θ' with less Ω to plentiful Ω with less θ'. The variation of Ag content hardly affects the potential of PFZ, and the corrosion resistance of the alloy depends mainly on the width of PFZ. With increasing Ag content, the precipitations on the grain boundaries are refined; the width of PFZ decreases and correspondingly, the corrosion passageway becomes narrow. The IGC resistance of Al-Cu-Mg-Ag alloy is enhanced with increasing Ag content.
HUTCHINSON C R , FAN X , PENNYCOOK S J , et al. On the origin of the high coarsening resistance of Ω plates in Al-Cu-Mg-Ag alloys[J]. Acta Materialia, 2001, 49 (14): 2827- 2841.
doi: 10.1016/S1359-6454(01)00155-0
2
REICH L , MURAYAMA M , HONO K . Evolution of Ω phase in an Al-Cu-Mg-Ag alloy-a three-dimension atom probe study[J]. National Research Institute for Metals, 1998, 46 (17): 6053- 6062.
3
RINGER S P , HONO K , POLMEAR I J , et al. Nucleation of precipitates in aged Al-Cu-Mg-(Ag) alloys with high Cu:Mg ratios[J]. Acta Materialia, 1996, 44 (5): 1883- 1898.
doi: 10.1016/1359-6454(95)00314-2
SONG M , XIAO D H . Effects of Cu and Mg content on microstructure and mechanical properties of Al-Cu-Mg-Ag alloy[J]. Heat Treatment of Metals, 2007, 32 (12): 64- 66.
DUAN A J , LIU Z Y , XU J , et al. Effect of Mg content on microstructure and mechanical properties of Al-Cu-Mg-Ag alloys[J]. Rare Metal Materials and Engineering, 2010, 39 (Suppl 1): 52- 55.
6
BAI S , ZHOU X W , LIU Z Y , et al. Atom probe tomography study of Mg-dependent precipitation of Ω phase in initial aged Al-Cu-Mg-Ag alloys[J]. Materials Science and Engineering:A, 2015, 637, 183- 188.
doi: 10.1016/j.msea.2015.04.052
SONG Y F , PAN Q L , FENG L , et al. Effects of Mg content on microstructure and mechanical properties of Al-Cu-Mg-Ag alloy[J]. The Chinese Journal of Nonferrous Metals, 2013, 23 (7): 1812- 1818.
8
BAI S , ZHOU X W , LIU Z Y , et al. Effects of Ag variations on the microstructures and mechanical properties of Al-Cu-Mg alloys at elevated temperatures[J]. Materials Science and Engineering:A, 2014, 611, 69- 76.
doi: 10.1016/j.msea.2014.05.065
LIU Y Q , ZHENG Z Q , LI S C . Microstructures and intergranular corrosion behavior of 2×××series Al-alloys with high Cu/Mg ratio[J]. The Chinese Journal of Nonferrous Metals, 2011, 21 (12): 3057- 3063.
10
CHANG C H , LEE S L , LIN J C , et al. Effect of Ag content and heat treatment on the stress corrosion cracking of Al-4.6Cu-0.3Mg alloy[J]. Materials Chemistry and Physics, 2005, 91 (2-3): 454- 462.
doi: 10.1016/j.matchemphys.2004.12.009
QI H , LIU X Y , LIANG S X , et al. Corrosion resistance of Al-Cu-Mg-Ag new heat-resistant Al alloy[J]. The Chinese Journal of Nonferrous Metals, 2015, 25 (11): 3033- 3039.
HE Z L , GAO W L , LU Z , et al. Effects of heat treatment on microstructure and properties of 7A85 aluminium alloy[J]. Journal of Materials Engineering, 2015, 43 (8): 13- 18.
13
BAYAZID S M , FARHANGI H , ASGHARZADEH H , et al. Effect of cyclic solution treatment on microstructure and mechanical properties of friction stir welded 7075 Al alloy[J]. Materials Science and Engineering:A, 2016, 649, 293- 300.
doi: 10.1016/j.msea.2015.10.010
LIU M , ZHANG K , DAI S L , et al. Fatigue performance of Al-Cu-Mg aluminum alloy for aviation[J]. Journal of Aeronautical Materials, 2014, 34 (1): 76- 81.
15
LI C , PAN Q L , SHI Y J , et al. Influence of aging temperature on corrosion behavior of Al-Zn-Mg-Sc-Zr alloy[J]. Materials&Design, 2014, 55, 551- 559.
16
GARG A , HOWE J M . Convergent-beam electron diffraction analysis of the Ω phase in an Al-4.0Cu-0.5Mg-0.5Ag alloy[J]. Acta Metallurgica et Materialia, 1991, 39 (8): 1939- 1946.
doi: 10.1016/0956-7151(91)90162-T