Establishment Of Cellular Automaton To Study On Grain Evolution For Electric Upsetting Process Of SNCrW Alloy

SNCrW,as a kind of heat-resistant alloys,has excellent high corrosion resistance,high strength,superior creep strength.For this reason,SNCrW is primarily used in manufacture of turbines components and exhaust valves on diesel engine.However,the fine comprehensive mechanical properties of SNCrW results in that the SNCrW has a poor workability.Thus,electric upsetting process is conducted during the production process of exhaust valves.During the electric upsetting process,the temperature of the part which undergone plastic deformation is very high,which resulted in dynamic recrystallization and dynamic recovery.It is well known that microstructure has a great influence on the mechanical property,this demands to study the SNCrW microstructure evolution law during the electric upsetting process.The commonly simulation methods is just used to analyze microstructure qualitatively by the empirical formula,this method is not capable of meeting the requirement that can study the influence of different process parameters on microstructure.Nowadays,the rapid development of computer science in the materials science field is giving us additional convenient and reliable tools to study the microstructure evolution quantitatively,such as Monte Carlo?phase field method and cellular automaton method.In the present paper,the cellular automaton method is adopted to analyze the microstructure evolution during the electric upsetting process.In this present paper,dynamic recrystallization model and the grain size model is established based on the isothermal compression stress-strain data of SNCrW.In addition,the principle of cellular automata is elaborate in detail.Subsequently,the electric upsetting process is simulated on the platform of finite element simulation software.The analysis of the simulation results indicates that the present automaton method has a good capability to study the SNCrW microstructure evolution during the temperature plastic deformation.The main contents and conclusions of this paper are shown in follows:(1)Based on the isothermal compression test,the true stress-strain data of SNCrW heat resistant alloy at the temperature range of 1203-1403 K and strain rate range of 0.01-10 s-1 is obtained,and then the dynamic recrystallization model and the grain size model for the SNCrW is established.(2)The fundamental principles of the cellular automaton method is detailed,and the cellular automaton model the simulation software comes with is divided into the dislocation density model ? dynamic recovery model ? dynamic recrystallization nucleation and growth model.(3)The established cellular automaton model is used to study the dynamic recrystallization process and the grain growth process.The relative errors between the simulated grain size and the experimental grain size indicates that the cellular automaton method is a reliable method that is able to study the microstructure evolution when the part undergoes the temperate plastic deformation.(4)The electric upsetting is simulated on the platform of Deform-3D,the validated cellular automaton model is used to analyze the microstructure evolution,it is also found that the errors between simulated grain size and experimental grain size of different locations are acceptable.