Influence of elastic tensile stress on aging process in an Al-Zn-Mg-Cu alloy

The effect of elastic tensile stress on the microstructure of 7075 Al alloy aged at 393-453 K for 1 h has been investigated in this paper. It was found that during the low temperature aging, the external stress lessens the size of the GPI zones. GPII zones are just identified in the stress-free aged condition. A new edge-on η′ platelet is observed in the stress-aged specimen. During the high temperature aging, the external stress promotes the formation of MgZn2 precipitates without changing the type of it. The peak microhardness value of the stress-aged specimens reaches 180 HV. The aging period of this alloy is shortened using the stress aging treatment.