Study On Microstructure Evolution Of Armco Iron In Hot Forging

As one of important industrial metal materials,Armco Iron has excellent mechanical properties,it is widely used in aerospace,energy,weapons and other fields.The microstructure uniformity and physical and mechanical characteristics of Armco Iron affect the accuracy and performance of parts in precision machining process.Microstructure evolution process of recrystallization fraction,dislocation density and grain size is studied to build the microstructure evolution model during hot forging,which has guiding significance in controlling microstructure.Uniaxial compression tests are carried on Thermecmaster thermal simulated test machine to determine stress-strain curves of DT4 E Armco Iron at different temperatures and strain rates.Recrystallization process is used to study the influence of strain rate and true stain on grain refinement.After compressing,grain growth process of DT4 E Armco Iron is studied by controlling holding time and heat temperatures during heat treatment.Internal relations of microstructure evolution of DT4 E Armco Iron are studied by combining recrystallized grain refinement,grain growth and stress-strain relationship.Based on the physical mechanism of microstructure evolution,internal variable method is used to correlate microscopic variables like dislocation density,recrystallization fraction and grain size with macroscopic variables like deformation temperature,strain rate and stress-strain to establish a uniaxial compression microstructure evolution model of DT4 E Armco Iron.The genetic algorithm optimization technique,combined with the experimental data,is used to calculate material parameters in microstructure evolution model.By comparing experimental data with prediction results,it is proved that the uniaxial compression microstructure model can accurately express viscoplastic characteristics and microstructure evolution rules of DT4 E Armco Iron in uniaxial compression.Microstructure evolution model of DT4 E Armco Iron is imported into finite element software DEFORM11.0 by user-defined subroutine to simulate twin-cone compression.Grain size,temperature and plastic strain distribution are obtained through the post processing.Twin-cone compression experiment is conducted to get the grain size at different location.The error of simulation results and experimental results of grain size is small,which indicates that microstructure evolution model can accurately predict the microstructure evolution rules during hot deformation process.