Influence of Retrogression and Re-Aging Parameters on the Microstructure and Hardness of Jet-Formed 7050 Alloy

In this paper, regression and re-aging treatment (RRA) was performed on the 7050 alloy, and the evolution in the microstructure of the 7050 alloy was observed by metallography and SEM. The effect of regression and re-aging treatment on the hardness of the alloy was investigated; the maximum hardness was 84.576 HRB at 180 °C/30 min. It was found that with the increase in regression treatment time, the size of the precipitates on the grain boundaries gradually increased, while the number of the precipitates inside the grain decreased accordingly. In the course of the experiment, the η’ (MgZn2) transforms into the η (MgZn2). As a result, the hardness of the alloy showed a decreasing trend. Meanwhile, the precipitates on the grain boundaries gradually increased in size, while the number of precipitates within the grain boundaries correspondingly decreased. These results reveal the influence of the re-aging treatment on the microstructure and mechanical properties of 7050 aluminum alloy, providing an important experimental basis for further optimizing the performance of the alloy.