Abstract:The effects of Cu on the peak aging precipitates, tensile properties and intergranular corrosion properties of 6000 series aluminum alloy were investigated by OM, TEM, HRTEM, tensile and intergranular corrosion tests. The results show that the addition of Cu promotes the precipitation of the peak aging phase of the alloy. With the Cu content increasing from 0wt% to 0.18wt% and 0.37wt%, the precipitate size of the peak-aged alloy decreases significantly, the volume fraction increases from 4.05% to 4.61% and 5.36%, and strength increases from 421 MPa to 448 and 459 MPa, respectively. According to HRTEM analysis, the main precipitates of the three alloys in peak aging state is β" phase, and L phase is also found in the alloy with 0.37wt% Cu. The addition of 0.18wt% Cu improves the intergranular corrosion resistance of the alloy, while the addition of 0.37wt% Cu decreases the intergranular corrosion resistance of the alloy. It is found that the addition of 0.18wt% Cu promotes the precipitation of β" phase in the alloy, and the width of the precipitation free zone (PFZ) at the grain boundary is refined to 51.92 nm. The addition of 0.37wt% Cu promotes the precipitation of the strengthened phase and changes the type of the precipitated phase. In addition, it is found that the addition of 0.37wt% Cu significantly increases the width of the PFZ at the grain boundary, and the PFZ width is 60.20 nm. Combined with aging precipitates, tensile strength and intergranular corrosion, it is found that the alloy with 0.18wt% Cu has excellent comprehensive properties.