Research On Microstructure Simulation Of Hot Deformation Of GH4698 Nickel-based Superalloy

With the development of high-end manufacturing industries such as aerospace,the demand for mechanical products is becoming more and more stringent,which requires not only "shaping" but also "controllability".GH4698 nickel-based superalloy occupies a very important position in the whole aerospace field due to its excellent mechanical and operational properties.For example,it is used to make guide blade,turbine blade,etc.However,the alloy has high alloying degree,poor plasticity,complex geometric structure and uneven deformation.It is a difficult problem to achieve "shaping" and "controllability" in the process of forming.Therefore,the research of the hot deformation behavior and microstructure evolution of GH4698 nickel-based superalloy has great guiding significance for improving the mechanical and use properties of the aeronautical products.Based on dislocation density theory and recrystallization kinetics model,a two stage constitutive model including the work hardening-dynamic recovery and the dynamic recrystallization was established on the basis of the dynamic recrystallization of the GH4698 nickel base superalloy.The correlation coefficient(R)is 0.986,and the absolute mean error(AARE)is only 4.5%.It shows that the two-stage constitutive model has good prediction accuracy and can be used to characterize the deformation behavior of GH4698 nickel-based superalloy under different thermal deformation conditions.The microstructure evolution behavior of the alloy was studied and the relationship between the deformation process parameters and microstructure evolution was revealed.Dynamic recrystallization kinetics model and recrystallization grain size model were established.On the basis of the finite element,the constitutive model and microstructure evolution model are embedded,and the thermo-force microstructure coupling numerical simulation platform for this alloy is set up.And predict the alloy microstructure evolution in the process of high temperature plastic deformation law.The influence mechanism of deformation temperature and strain rate on recrystallization volume fraction,recrystallization grain size and average grain size were revealed.By comparing the experimental and the simulated value of the grain size of the dynamic recrystallization,it is found that the experimental value has a good correlation with the simulated value,and the error is distributed in the 15% error line.The feasibility of microstructure evolution simulation using cross-scale numerical simulation is presented to provide scientific basis for the process development and optimization of new products.Based on cellular automata method,the dynamic recrystallization microstructureevolution during hot compression process is researched.And the influence of deformation temperature,strain rate and strain on the evolution of dynamic recrystallization was researched.The results show that the grain percentage of larger than 80μm is decreasing with the increase of strain,and gradually decreases with the increase of deformation temperature,and increases with the increase of strain rate.The grain percentage of less than 20μm gradually decreases with the increase of deformation temperature,and increases with the increase of strain rate.The grain percentage of20~80μm gradually increases with the increase of deformation temperature and decreases with the increase of strain rate.Revealing the relationship between process parameters and grain evolution by cellular automata simulation plays an important role in improving the mechanical properties of products.