Two-stage double-peak aging process, aging hardening characteristics and mechanical properties are
systematically studied by design of the L9(34) orthogonal test in this paper. The second stage in the whole aging has
a decisive impact on the mechanical properties of the alloy, hardness and strength are more sensitive to final aging
temperature while plasticity and toughness are more to final aging time. It can be found that there is an optimal dual
aging process corresponding to the different performance, when use double-peak to optimized the process of high plasticity,
high toughness coming from the orthogonal test. It is found the performance index can not reach the theoretical
optimum maximum, and only a relative optimal process is obtained. We found that the best two-stage double-peak aging
process is:105℃ /4 h+155℃ /70 h.