Numerical Simulation Of Multi-Scale Coupling Of Nickel-Base Superalloy By Laser Additive Manufacturing

Due to its short forming cycle,high flexibility,and the ability to directly form complex internal structures.Laser additive manufacturing technology is used more and more in the field of rapid manufacturing and repair of aerospace components.The thermal process and the microstructure of the laser additive manufacturing process determine the performance of the part,which is the hot point of current research.However,its pool solidification has the characteristics of non-equilibrium high temperature transient.It is difficult to observe the micro structure through experiments.The numerical simulation method is used to predict the microstructure of the molten pool solidification process.Using finite element method to simulate the additive manufacturing process,and calculating the temperature field of molten pool.Then the macro-temperature field and cellular automata micro-simulation method are couped calculation,which can predict the laser additive manufacturing process crystal nucleation and growth process.In this paper,the microstructure evolution model of the laser pool during solidification is established,and the temperature field in the laser additive manufacturing process and the solidification microstructure of the molten pool are simulated.The main research contents include:(1)The mechanism of metal solidification is analyzed.The key factors of grain nucleation and growth during solidification are analyzed.Four numerical methods for solidification microstructure evolution are summarized.At last,Selecting the numerical simulation method is used in this paper.(2)The cellular automata and finite element are combined to establish dendrite nucleation and growth model of laser cladding pool.Due to the very rapid cooling rate of the molten pool,this model considers the effects of temperature distribution,solute distribution,dendrite tip curvature and dendrite growth anisotropy on dendrite nucleation and growth.(3)Based on the theory of laser surface cladding temperature field,the temperature field in the laser cladding process is numerically simulated with the "life and death cell technology of ANSYS.The effect of process parameters on the temperature field of molten pool by laser additive is studied.Finally,a set of optimal parameter combination is obtained,and the temperature field simulation and analysis are carried out with the set of parameters.The macroscopic temperature field data are obtained and the data are processed to lay a foundation for the kinetic equation of grain growth in the molten pool.(4)The dynamic simulation of equiaxed grain growth under uniform temperature field is realized by using the established model.The data obtained from the laser cladding temperature field are applied to the cellular automata simulation to simulate the dendrite growth in the central columnar zone of the molten pool.The process parameters are changed to study the influence of technological parameters on the columnar crystal morphology.