Study On Variation Of Microstructures And Properties Of GH4169 Alloy In Different Solution Heat Treatment

In the paper, the influence of solution treatment on the microstructure and properties of the radial forged and hot continuous rolling GH4169 alloy are investigated by means of solution treatment, properties measurement and microstructure observation.Conventional tensile properties and work hardening behavior of radial forged GH4169 alloy is studied by quasi-tensile test. After three different solution treatments, grain size numbers of all radial forged GH4169 alloy samples are 9.5, but distribution and precipitation patterns ofδ-phase is different in the sample, the 8-phase content increases with the raise holding time at 870℃. It is found that the work hardening kinetics of radial forged GH4169 alloy is consonant with the Hollmon Equation, and content, distribution and precipitation patterns ofδ-phase have certain effect on yield strength, elastic modulus, strain-hardening procedure and fracture surface of room temperature tensile specimens of radial forged GH4169 alloy.Grain growth behavior and its kinetics during solution treating process of hot continuous rolling (HCR) GH4169 alloy have been investigated by using chamber type electric resistance furnace and optical microscope. The experimental results show thatδ-phase dissolution temperature of HCR GH4169 alloy is from 990℃to 1000℃, and 8-phase in the superalloy greatly restrain grain growth. The solution treatment at temperature belowδ-phase dissolution leads to little variation of grain size and solution treatment at temperature aboveδ-phase dissolution leads to rapid grain growth for HCR GH4169 alloy. The grain growth kinetics at temperature aboveδ-phase dissolution shows that grain growth exponentially increases with the increasing solution treating temperature. At the temperatures from 1000℃to 1050℃, the activation energy value for grain growth in HCR GH4169 alloy is 223.849 KJ/mol, which means that the grain growth mechanism is self-diffusion-controlling process, and the grain growth kinetics eqution are given. The effects of three different heat treatments on microstructures and creep properties of HCR GH4169 alloy have been investigated by creep test and scanning electron microscope. It is found that different heat treatments effect on grain size of HCR GH4169 alloy. Grain size of the sample after direct ageing (DA) treatment is smallest of all, Grain size of another sample after high standard treatment (HST) is biggest of all. The content of 8-phase increases with increasing time of solution heat treatment, and 8-phase is mainly growed at the grain boundary. Under 650℃/725MPa experimental conditions, the creep properties of HCR GH4169 alloy after DA treatment is best, the creep properties of HCR GH4169 alloy after HST is worst. Rupture fracture of creep specimens after heat treatment are observed, the fracture mode is mainly intergranular fracture.