The role of Si on microstructure, mechanical and local corrosion behaviors of an Al-Cu-Mg-Si alloy with high Cu/Mg ratio

The influences of Si (0.65-1.28 wt%) on the microstructure, mechanical, impact toughness and local corrosion behaviors of an Al-Cu-Mg-Si with high Cu/Mg ratio has been investigated. The results showed that the area fraction of insoluble particles Q phase increased with the increase of Si content, and a small amount of Si phase appeared at high Si content. The ageing precipitates was theta' and Q' phase, and the number of Q' phase significantly increased with the increase Si content. Si didn't obviously accelerate age-hardening response, nor effectively improve peak hardness in the range of 0.65 <= Si <= 1.28 wt%. The strength of the alloy first increased and then decreased, while the impact toughness and local corrosion properties decreased with the increase of Si content. The fracture and corrosion mechanism have been discussed in detail. (C) 2019 Elsevier B.V. All rights reserved.