Study on a new retrogression and re-aging treatment of spray formed Al-Zn-Mg-Cu alloy

Conventional retrogression and re-aging (RRA) treatment could not be put to good use for combination property of Al-Zn-Mg-Cu alloys. The new RRA treatment fitted for spray formed Al-Zn-Mg-Cu alloy was investigated by transmission electron microscope, tensile, and conductivity tests. The results show that the pre-aging treatment with under aging of 120 °C for 16 h is beneficial for the redissolution of matrix precipitates during retrogression treatment. With the retrogression of 200 °C for 8 min, grain boundary precipitates are discrete and the corrosion resistance of the alloy is drastically increased. After re-aging (120 °C for 24 h) the strength of the alloy is increased again. According to the above-mentioned new RRA treatment, the ultimate tensile strength, yield strength, elongation, and conductivity of the alloy are 791 MPa, 736 MPa, 8.5%, and 39.5% IACS respectively, which is higher than that after conventional RRA treatment.