Effect of different aging treatment on high temperature properties of die-forged Al-5.87Zn-2.07Mg-2.42Cu alloy

High temperature tensile test over the temperature range from 100 degrees C to 250 degrees C of die forged Al-5.87Zn-2.07Mg-2.42Cu alloy were carried out and the effect of aging treatment on microstructures and mechanical properties of alloy were studied. The strength of alloys processed with peak aged (T6), over aged (T73) and retrogression and re-aging (RRA) treatment suffered from different extent of decreasing for the increase of the stretching temperature. Among them, the RRA alloy has the most obvious drop in tensile strength, which has dropped from 615 MPa to 268 MPa with temperature rising from room temperature to 250 degrees C. While T6 and T73 alloys drop by 338 MPa and 333 MPa, respectively. With the increase of test temperature, the coarsening rate of precipitates in RRA sample is faster than that of T6 and T73, resulting in more significant decrease in the high temperature strength. The T73 sample exhibits good stability of high temperature mechanical properties, due to the slowing coarsen rate of precipitates.