The evolutions of microstructure and stress-rupture properties were investigated during aging at 700 and 900 ℃. With the increase of aging time at 700 ℃, the morphology, the size and the distribution of γ′ and carbides did not change, and the stress-rupture time was stable. During aging at 900 ℃, γ′ was coarsened to be worm-shaped. The worm-shaped microstructure was stable from 1007 h to 2014 h. The needle-like TCP phase was precipitated when the alloy was aged for 2014 h, but its content was very small. The stress-rupture time was only 30 h when the alloy was aged for 500 h. It was shortened by 50% in contrast to heat treated state. The stress-rupture time did not change from 1007 h to 2014 h