Effect of two-stage ageing on microstructures and properties of 1973 aluminum alloy

The two-stage ageing on the microstructures and properties of 1973 aluminum alloy were studied by means of transmission electron microscopy (TEM), hardness and conductivity measurements. The results show that the temperature and time of the second-stage ageing have a key effect on the properties of the alloy, while the temperature of the first-stage ageing has little effect on them. The best two-stage ageing process for this alloy is: (120°C, 6 h) + (160°C, 16 h). Under this condition, the hardness and electrical conductivity of this alloy are 191HV and 38.0% (IACS), respectively. The microstructure of this alloy is that the nano scale precipitates disperse inside the grain, and the coarse-discontinuous precipitates occur along the grain boundaries. The precipitated-free zones (PFZ) appear on the grain boundaries. The main precipitates are η and η' phases, and with minous GPII zone.