Finite Modeling And Applying Of Low ?CSL Grain Boundary Proportion Based On Ni-based Superalloy Electric-Thermal-Mechanical Coupling Simulation

Low CSL?3ⁿ grain boundary can effectively improve the nickel-based super alloy oxidation resistance,corrosion resistance and mechanical properties.High density low CSL?3ⁿ grain boundary is great significant to deal with power decrease and even sudden destruction problem for nickel-based super alloy valve body caused by low grain boundary network cracking degree.In this paper,the nickel-based super alloy Nimonic 80A valve blank was taken as the research object.A nickel-based super alloy electric-thermal-mechanical coupling finite element model with proportion of low CSL?3ⁿ grain boundary was established in Msc.Marc finite element software by the secondary development of subroutines.The visualization of low CSL?3ⁿ grain boundary density(BLDⁿ_?3)dynamic response variation during the electric upsetting was achieved to study distribution of BLD?3ⁿ and its influencing factors.These simulation results were verified by the trial-manufacture experiments for nickel-based super alloy valve body in electric upsetting,which can provide theoretical guidance for the grain boundary control in actual production of electric upsetting.The main contents and conclusions are as follows:?1?The isothermal compression experiments for Nimonic 80A Ni-based superalloy were implemented at the temperature range of 1000-1150?and the strain rate range of0.01-10 s^-1,and the compression samples were characterized using EBSD micro technology.Based on theory and statistics,BLDⁿ_?50?3?28?c?10?b/d_AV,the phenomenological relational model between BLD?3ⁿ and grain size has been established.?2?The dynamic recrystallization model,grain growth model and the phenomenological relational model were embedded into Msc.Marc finite element softwarebythesecondarydevelopmentofsubroutines.The electrical-thermal-mechanical multi-field multi-scale coupling finite element model of isothermal compression were constructed based on above subroutines,and the corresponding nonlinear adaptive load current and load speed were designed.?3?On the basis of simulation results,the variation and corresponding influence factors of BLD?3ⁿ,dynamic recrystallization fraction and grain size are analyzed during compression.The analysis results showed BLD?3ⁿ increased with the increasing deformation,and then decreased with the increasing deformation,which demonstrated the built model had well effectiveness and generalization ability.?4?The visualization technology of BLD?₃ⁿ built on the above was applied to electric upsetting.The temperature filed,equivalent plastic strain filed and grain structure distribution were analyzed,and the accompanying relationship between BLD?3ⁿ and dynamic recrystallization were deeply elaborate.?5?A trial-manufacture experiment of electric upsetting was designed and implemented based on processing parameters used in simulation.According to the contrastive analysis between trial production of electric upsetting and simulation,the simulation results match well with the experiment results,which demonstrates that the electrical-thermal-mechanical marco and micro multi-scale coupling finite element model involing BLD?3ⁿ are reliable.Meanwhile,the results indicate the inhomogeneous of the low CSL?3ⁿ grain boundary is closely associated with uneven temperature and uneven deformation along with the axial,radial and 45°direction.It is concluded that low CSL?3ⁿ grain boundary proportion and distribution can be regulated and controlled by adjusting the process parameters to aheieve homogenization temperature and deformation.