Cellular Automaton Modeling Of Microstructural Evolution In HC276 Superalloy During Hot Deformation

In recent years,the aerospace,nuclear industry,and petrochemical fields have developed rapidly,which has promoted the research and development of superalloys.Ni-Cr-Mo-based superalloy HC276 is a typical superalloy.It has good resistance to pitting corrosion and stress corrosion,and has good stability in various oxidizing and reducing media,so it is widely used in a series of fields such as aerospace and marine science.The processing of HC276 superalloy will be accompanied by many hot deformation mechanisms,including dynamic recrystallization and metadynamic recrystallization.Different working processes will make the microstructure different.The difference in microstructure determines the difference in mechanical properties and other properties of materials.Therefore,it is necessary to adjusting the process to obtain HC276 superalloy material with good performance.In the actual production process,it is difficult to observe the evolution of the microstructure.Computer simulation can effectively solve this problem.This paper combines the cellular automaton(CA)with the hot deformation mechanism to simulate the dynamic recrystallization,metadynamic recrystallization and dynamic recrystallization under variable working conditions of HC276 superalloy during hot deformation.The main research contents and conclusions are as follows:1.Single pass hot compression experiments was carried out for HC276 superalloy sample by the thermal simulation experimental machine.Based on the dislocation density growth theory,recrystallized nucleation theory,recrystallized grain growth and other physical metallurgical principles and the experimental results to establish the dynamic recrystallization model of cellular automaton.The results show that the CA model can effectively simulate and predict the evolution of the microstructure during the hot deformation process.The results show that with the increase of hot processing temperature,the average recrystallized grain size and recrystallized fraction of the material will increase to a certain extent;and the increase of strain rate will make the average recrystallized grain size and recrystallized fraction of the material will be a certain degree of reduction.2.Two pass hot compression experiments was carried out for HC276 superalloy sample by the thermal simulation experimental machine.Based on the physical metallurgy principle in the hot compression process and the principle of grain growth in interval and the experimental results,a metadynamic recrystallization model of cellular automaton is established.The results show that factors such as pass interval time and temperature will affect the microstructure.The extension of pass interval time and the increase of temperature will increase the degree of metadynamic recrystallization,and both the recrystallized grain size and the recrystallized fraction will increase.Through the comparison of simulation and experimental results,the CA model can effectively simulate and predict the metadynamic recrystallization process of materials.3.Single pass hot compression experiments with a variable strain rate was carried out for HC276 superalloy sample by the thermal simulation experimental machine.Based on the experimental results,the single pass dynamic recrystallization model,and the hot compression process is divided into two stages with different strain rates,a dynamic recrystallization under variable working conditions model of cellular automaton is established.The results show that keeping the one stage strain rate unchanged,the smaller strain rate in the other stage,the larger recrystallized fraction and recrystallized grain size of the material.Through the comparison of simulation and experimental results,the CA model can effectively simulate and predict the dynamic recrystallization under variable working conditions process of materials.