Precipitation behavior and mechanical properties of Al-1.0Mg-0.6Si-Cu (wt.%) alloy controlled by Cu content

The precipitation and intergranular corrosion (IGC) behavior of Al-1.0Mg-0.6Si-Cu (wt.%) alloys with the addition of Cu ranged from 0.3 to 0.6 wt.% were investigated by optical microscope and transmission electron microscopy. The results indicated that the Cu addition significantly improves the hardness of the alloys during under-aging progress by accelerating the precipitation of GP zones. The addition of Cu has changed the composition of precipitation and facilitated the formation of beta ''-Mg5Si6 precipitates with high density and fine distribution. When the Cu content is added to 0.6 wt.%, the type of precipitation has changed. In addition to the needle-shaped beta '' phase, a new-plate Q ' phase precipitated during peak-aging conditions. The 0.6 wt.% Cu alloy shows superior strength with tensile yield strength of 328 MPa, ultimate tensile strength of 368 MPa, and elongation of 16.0%. However, the IGC resistance decreased with the Cu content increasing from 0.3 to 0.6 wt.%, which mainly resulted from the segregation of Cu elements and the formation of continuous Q ' precipitates at the grain boundaries.

Automated summary

The precipitation and intergranular corrosion behavior of Al-1.0Mg-0.6Si-Cu (wt.%) alloys with added Cu ranging from 0.3 to 0.6 wt.% were investigated. Results showed that the addition of Cu significantly improved the hardness of the alloys during under-aging by accelerating the precipitation of GP zones. Cu addition changed the composition of precipitation and facilitated the formation of beta ''-Mg5Si6 precipitates with high density and fine distribution. However, the intergranular corrosion resistance decreased with increasing Cu content, mainly due to the segregation of Cu elements and the formation of continuous Q ' precipitates at the grain boundaries.