The Adjusted Method And Optimization Of Process Parameters For Valve Billet With Ni-based Superalloy During The Electric Upsetting To Achieve Grain Refinement And Uniform Distribution

This paper mainly studied the adjusted method and optimization of process parameters for Ni-based superalloy during the electric upsetting to achieve grain refinement and uniform distribution.According to the parameters range with fine grain identified from processing map and deformation mechanism map,the electric upsetting parameters were optimized,which providing the theoretical guidance for practical electric upsetting production.Firstly,the isothermal compression experiments of Nimonic 80 A heat-resisting alloy were implemented to acquire the rue stress-strain data by thermal physical simulation testing.The GA-SVR support vector regression model was constructed based on the true stress-strain data and it was used to expand the stress-strain data.Then,the power dissipation maps,instability maps,processing maps and deformation mechanism maps were plotted to identify the parameters range with fine grain.Additionally,the nonlinear loading paths of electric upsetting parameters were designed and the multi-field and multi-scale coupling finite element model for electric upsetting was established.According to the results,the response relationship between the target of grain refinement and uniform distribution and electric upsetting parameters.In addition,a multi-objective genetic algorithm was utilized to optimize process parameters in electric upsetting.The main contents and conclusions of this paper are as follows:(1)The axisymmetric isothermal compression experiments were implemented to collect the stress-strain data on Gleeble-3500 at the temperature range of 1000-1200? and the strain rate range of 0.01-10 s-1.The GA-SVR support vector regression model was constructed based on the true stress-strain data and it was used to expand the stressstrain data.(2)According to the experimental and predicted stress-strain data,hot processing map and deformation mechanism map of Nimonic 80 A nickel alloy were established.The identified steady recrystallization process parameter intervals of temperature and strain rate of this alloy are 1075-1125? and 0.045-0.32 s-1,respectively.(3)Based on the steady recrystallization parameter interval identified by the deformation mechanism diagram,design the nonlinear loading path in electric upsetting process.Combined with the grain size model of Nimonic 80 A nickel superalloy,establish a multi-scale and multi-field coupling finite element model of electric upsetting,and quantitatively analyze the blank temperature,deformation state,the grain size and distribution in electric upsetting billet process.(4)The Box-behnken experiment design method was used to design the finite element simulation scheme of electric upsetting,statistically analyze simulation results,and establish dynamic response relationships among grain size & grain inhomogeneity and main process parameters(the clamping length,back speed of anvil,upsetting speed of upsetting cylinder,and heating current).A multi-objective genetic algorithm was utilized to optimize process parameters in electric upsetting.The grain size & grain inhomogeneity of final optimization results are 32.6933 ?m and 6.5621 ?m,respectively.Compared with the original parameters,two target values were reduced by 14.8% and 34.7%,respectively.