Study Of Microstructures And Properties Of GH4169 Alloy

In this paper, the low-temperature ductility of GH4169 alloy and the creep properties of hot continuous rolling(HCR) GH4169 alloy after different heat treatments have been investigated. The microstructures of above alloys are observed by SEM. The low temperature mechanical properties and creep performance of GH4169 alloys were studied.The central and edge parts of GH4169 alloys are impacted at low temperature. It is found that the alloy grain size affects the impact energy. Then, the samples are impacted at room temperature researching the impact energy at low and room temperature. In addition, the impact energy is compared between forged and hot rolled samples and the morphology of impact fracture surface was observed by SEM. The results show that the impact energy of alloy GH4169 decreases with the alloy grain size because of the stress and dislocations concentration at grain boundaries. There is less content of P, Mn, Si and more content of Ni in the alloy. The magnitude of the impact energy is nearly the same at the low and room temperature because of more slip systems. The toughness of hot rolled samples is much better than those of forged sample. The impact fractures are of dimple surfaces.The effects of three different heat treatments on microstructures and creep properties of (HRC) GH4169 alloy have been investigated. It is found that the grain sizes of GH4169 alloys increase slightly (9 grain size) and the twins are found in the grains after HST, ST treatment. The grain sizes of alloy are smaller (10 grain size) and more twins are found in the grains after DA treatment. A large number of continuous short rod-likeδphase mainly precipitates after the HST treatment at grain boundaries, some short discontinuous rod-likeδphase precipitates after ST treatment at grain boundaries,δphase doesn't precipitate after DA treatment. The content ofδphase increases with increasing time of solution heat treatment. Under 650℃/725MPa experimental conditions, the HCR GH4169 after DA heat treatment has powerful creep resistance and long life time, while the HCR GH4169 after HST heat treatment has short life time. The fracture mode of creep specimens after heat treatment is of intergranular fracture.