Phase Field Simulation Of Peritectic Transformation Of Fe-C Binary Alloy

The structure of the microstructure determines the performance of the casting under working conditions.Therefore,it is important to control the formation of the metal microstructure correctly and effectively,which has profound scientific research and engineering guidance significance.During the molding of the metal,Various parameters influence the growth morphology of the microstructure.However,this process is difficult to observe directly by experimental methods.The numerical simulation of the phase field method provides effective conditions for studying the formation of microstructures during molding of the metal,and the formation of microstructures can be directly observed.Numerical simulation not only effectively saves the cost of microstructure research,shortens the research cycle,but also can quantitatively analyze the relationship between various parameters and microstructure,which provides theoretical guidance for the research of process control during the molding of the metal.Phase field method is an effective calculation method for simulating the microstructure of metal,and can describe the evolution of micromorphology.In recent years,the simulation study of phase field method has gradually changed from single-phase to multi-phase.The phase field model has been continuously improved,so that it is more practical to simulate the process of metal phase transition.At present,it is widely used to study the micro-morphology during the phase transition of materials.This study proposes a model of continuous phase transformation in a multiphase field,and uses it to take Fe-C binary alloy as an example to simulate the evolution of micromorphology during the peritectic phase transition of equiaxed and dendritic ?grains was simulated.Simulation results show: During the peritectic phase transformation of the equiaxed ? grains,the interface migration rate M??> M?L.The ?phase deviates from the liquid/solid interface and grows toward the inside of the ?phase.The enrichment of solutes at the ?/? interface caused partial melting of the ?phase at the three-phase node,resulting in(L+???)transformation.When the equiaxed and dendritic ? grains undergo a peritectic phase transition in the liquid phase,the ? phase as a shell surrounds the ? phase to grow.After the peritectic reaction ends,a layer of ? phase core-shell is formed.After the peritectic reaction wascompleted,a ?-phase core-shell is formed around the ?-phase.After the ? phase was surrounded by the ? phase completely,the peritectic phase transition changes from a peritectic reaction to a peritectic transition.When the peritectic phase transformation of the equiaxed ? grains occurs,the degree of undercooling affects the growth rate of the ? phase.As the degree of undercooling increases,the driving force of the peritectic reaction increases,the growth rate of the ? phase accelerates,and increasing the number of ? phase surrounded by the ? phase.After the dendritic ? phase is surrounded by the ? phase completely,the membrane shell isolates the L phase from the ? phase,so that the peritectic phase transition changes from a peritectic reaction to a peritectic transformation.During the subsequent peritectic transformation,austenite It keeps growing and finally fills the entire simulation area.During the peritectic transformation,the average rate of austenite growth towards the L phase is significantly greater than the average rate of growth into the ? phase ferrite.This is because the diffusion coefficient of carbon atoms in the liquid phase is much larger than that in the solid phase.The peritectic reaction rate is related to the curvature of the nucleation site of austenite.The rate of peritectic reaction during nucleation under a large curvature interface is faster than that under a small curvature interface.The curvature of the nucleation position only affects the speed of the peritectic reaction,and has no obvious effect on the growth of austenite towards the L phase and ? phase ferrite during the later peritectic transformation.