Abstract: Effect of aging time on microstructure, hardness and high temperature tensile properties of GH4169 alloy under the tested conditions of over-temperature service at 900 ℃ were studied. The results show that with the extension of aging time, the δ phase is precipitated from the grain boundary with a short rod shape, and then precipitated the whole grain with long needles; the grain is grown at the initial stage of aging, and with the δ phase gradual precipitating along the grain boundary, the phenomenon of grain growth is disappeared. The strengthening phase of the alloy is dissolved and transformed when the GH4169 alloy aged at 900 ℃, which results in the microhardness of the alloy dropping sharply from 44.0 HRC to 13.6 HRC, but the microhardness is changed a little with the increase of holding time. The precipitation of δ phase has a significant effect on the high temperature mechanical properties of the alloy. The proper amount of precipitation can increase the tensile strength and high temperature plasticity of the alloy. A large amount of precipitation results in a decrease of tensile strength and a deterioration on the high-temperature plasticity. The high temperature tensile of the alloy after different aging treatments is a typical elastic-uniform plastic deformation, and the deformation fracture mechanism is a microporous aggregate fracture.

Key words: GH4169 alloy, δ phase, aging treatment, microstructure, high temperature tensile