Characterization of precipitation microstructure and properties of 7150 aluminium alloy

The precipitation microstructure and the associated hardness and electrical conductivity have been systematically studied in a 7150 alloy during the ageing treatment. The evolution of the GP zones during the one step and the two step ageing processes is discussed in details. Experimental results show that the electrical conductivity of the alloy treated in the two step ageing regime is higher than that of the alloy treated in the one step ageing regime. The two step ageing regime increases the stability of GP I zones and restrains the coarsening of precipitates. During the two step ageing treatment, GP I zones are present when the ageing temperature at the second stage is 160 °C (36 h), which could not be detected in the one step ageing for short times at the same temperature. Both the GP I and GP II zones disappeared after ageing for 4 h at 180 °C. The achievement of the high strength of the alloy is ensured by a large volume fraction of fine GP zones and η′ precipitates.