Performance of Precipitates in the Stress Aging Treatment of 7075 Al Alloy

The effect of elastic stress on the precipitation process of 7075 Al alloy aged at 438 K for 1 hour has been investigated in this paper. The mechanical properties have been measured by hardness testing and scanning electron microscopy (SEM) and the microstructures have been characterized by optical microscopy (OM), together with transmission electron microscopy (TEM). Results indicate that the microhardness can reach 180 HV after a 25 MPa elastic tensile stress aging treatment, much higher than the stress-free ones'. The fracture is more brittle and the formation of the precipitates is promoted in the case of the stress-aged specimen. Our study provides a new process to bring down the energy consumption.