Research On High Temperature Mechanic Behavior And Microstructure Performance Calculation Of GH4742 Superalloy

With the development of aviation industry, the GH4742 supperalloy has been widely used in turbine disc, heavy ring, compressor plate, fasteners and other components, because the content of γ’ strengthening phase is high, making it has a higher using temperature(550 ℃ ~ 550℃), and excellent high temperature mechanical properties. The research of GH4742 supperalloy is mainly concentrated on smelting process. As-cast dendrite composition segregation, elements distribution and organizational characteristics after different homogenization treatment. Hot deformation behavior, dynamic recrystallization influencing factors, nucleation mechanism and model building. The influence of different heat treatment on the microstructure and mechanical properties, etc. But the research of GH4742 supperalloy microstructure how to influence the high temperature flow stress, strain hardening rate and the research dynamic recrystallization critical condition is less. Therefore, making use of nickel-based supperalloy flow stress calculation model to study the alloy high temperature plastic deformation behavior for the high temperature deformation process parameters optimization and organization of predictive control is particularly important.This paper, mainly adopts flow stress model to calculate true stress-strain curve of GH4742 supperalloy under different deformation conditions and microstructure. First, it compared and analyzed the data obtained by experiment and theoretical calculation of peak stress and yield stress, verifying the theoretical calculation model in calculating high temperature true stress-strain curve of GH4742 nickel-based superalloy is feasible. Then, according to the microstructure after different heat treatment calculated and drew the true stress-strain curve. It found that GH4742 supperalloy has strong temperature and strain rate sensitivity. The size and content of the precipitated phase have great impact on the stress-strain curve. precipitated phase owns a critical particle size, the strength of GH4742 supperalloy at the critical particle obtains maximum value, whether for the precipitate phase mixed with gross γ’ phase, for stress the size of the precipitated phase has the same influence.Grain size and gross γ’ size in precipitation phase have very little effect on the stress-strain curve.Work hardening rate under different deformation condition and organization was calculated relying on the true stress-strain curve. We found that work hardening of GH4742 supperalloy began from stage III. With the increase of stress, strain hardening rate fell particularly fast, and the curve slope of stage IV is obvious less than stage III. Therefore, the higher temperature and the lower strain rate are instrumental to the stage V. Grain size and gross γ’ size of precipitation phase have little impact on the work hardening rate curve. Precipitated phase content and size have a greater influence on the work hardening rate curve. With the increase of content of precipitated phase, the curve moves to the right; The greater stress of the precipitated phase size, the easier it is to come out work hardening stage V.Critical conditions of dynamic recrystallization under different deformation conditions and microstructure were calculated according to corner feature in hardening rate curve. Dynamic recrystallization critical stress and critical strain decrease with the increase of deformation temperature and increase with the rise of strain rate. Grain size and gross γ’ phase size of precipitation phase relatively have very little influence on dynamic recrystallization critical condition. The influence of precipitated phase content and size on the critical condition is very great, with the increase of precipitated phase content, the critical stress and the critical strain present increasing trends. With the increase of the precipitated phase size, the critical stress reduced after the first increases, but the trend of critical strain presents the opposite trend; they both obtained extremum at 30 nm. The percentage of small size γ’ phase in precipitated phase also has certain influence on dynamic recrystallization critical condition. The critical stress increases with small size γ’ phase content increases, with the critical strain decreases as the small size γ’ content increases.