摘要
As a structural material with low density and high strength, super-highstrength aluminum alloys have a future for wide application. However, its poor stress corrosionresistance (SCC) restricts further development. In present, retrogression and re-ageing (RRA)treatment, which can improve both strength and SCCR of 7XXX series alloy, is a best method to solvethis problem. The effect of RRA treatment on the microstructure evolution of a new type lowfrequency electric-magnetic casting Al-9.OZn-2.45Mg-2.2Cu-0.15Zr alloy was investigated using DSCand TEM technologies. The results show that the typical microstructure of the alloy at T6 conditionis characterized by both fine eta' and GP zone homogeneously distributed in the matrix andcontinuous r) particles occurred on the grain-boundary. After RRA treatment, the matrixprecipitations are mainly fine and dispersed eta' and eta phases, being coarser and more stable thanthat from T6 temper. While, the grain-boundary microstructure is very close to that resulting fromT73 temper. High retrogression temperature and long retrogression time leads to a more stablemicrostructure after re-ageing.
As a structural material with low density and high strength, super-highstrength aluminum alloys have a future for wide application. However, its poor stress corrosionresistance (SCC) restricts further development. In present, retrogression and re-ageing (RRA)treatment, which can improve both strength and SCCR of 7XXX series alloy, is a best method to solvethis problem. The effect of RRA treatment on the microstructure evolution of a new type lowfrequency electric-magnetic casting Al-9.OZn-2.45Mg-2.2Cu-0.15Zr alloy was investigated using DSCand TEM technologies. The results show that the typical microstructure of the alloy at T6 conditionis characterized by both fine eta' and GP zone homogeneously distributed in the matrix andcontinuous r) particles occurred on the grain-boundary. After RRA treatment, the matrixprecipitations are mainly fine and dispersed eta' and eta phases, being coarser and more stable thanthat from T6 temper. While, the grain-boundary microstructure is very close to that resulting fromT73 temper. High retrogression temperature and long retrogression time leads to a more stablemicrostructure after re-ageing.
