Effects of retrogression heating rate on microstructures and mechanical properties of aluminum alloy 7050

The effects of the retrogression heating rate (340 °C/min, 57 °C/min, 4.3 °C/min) on the microstructures and mechanical properties of aluminum alloy 7050 were investigated by means of hardness measurement, tensile properties testing, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that the retrogression heating rate significantly affects the microstructures and mechanical properties of the alloys treated by retrogression and re-aging (RRA) process, and it is found that the medium rate (57 °C/min) leads to the highest mechanical properties. The strengthening phases in the matrix are mainly the fine dispersed η' precipitates and GP zones, and the grain boundary precipitates are coarse and discontinuous η phases.