Effect of Ce element content on microstructure and corrosion resistance of highly-alloyed Al-Zn-Mg-Cu-Zr-Ti alloy
(Institute of Advanced Manufacturing and Modern Equipment Technology, Jiangsu University, Zhenjiang 21200, China)
Abstract: To effectively improve the corrosion resistance of aluminum alloys without affecting their strength, the effect of Ce content on the microstructure, stress corrosion, intergranular corrosion, and exfoliation corrosion resistances of Al-11.3Zn-3.1Mg-1.2Cu-0.2Zr-0.1Ti alloy was investigated. The results showed that the addition of Ce formed the (Zn,Al,Cu)22Ce3 phase with a size of 100 nm, which enhanced the recrystallization resistance of the alloy, increased the number of low-angle grain boundaries and dislocation density, refined the grains, promoted the phase transition from GP zone to η'''' phase, and promoted the size and discontinuity of precipitates at grain boundaries. All Ce-added alloys exhibited the higher resistance to corrosion. The alloy with 0.15 wt.% Ce possessed the optimal corrosion resistance along with the strength and elongation at slow strain rate of 744.8 MPa and 4.6%, respectively, in 3.5 wt.% NaCl solution. The minimum depth of intergranular corrosion and exfoliation corrosion was achieved as well.
Key words: Al-Zn-Mg-Cu alloy; microalloying; stress corrosion cracking; exfoliation corrosion; intergranular corrosion