Simulation Of Growth Behavior And Microstructure Evolution During Solidification Of Graphite

Grey cast iron plays an important role in China’s heavy industry because of its excellent mechanical and casting properties.The microstructure of grey cast iron determines its macroscopic properties,especially the graphite form in grey cast iron which plays a decisive role in its properties.However,solidification of gray cast iron has been a very complex research subject for a long time,because the as-cast microstructure of gray cast iron is the matrix composed of ferrite and pearlite,which is the result of the solid-state transformation of primary austenite at eutectoid temperature.This transformation masked the original austenite structure.However,the interaction between primary austenite eutectic austenite and graphite during solidification is not well revealed by the traditional metallographic techniques.With the rapid development of computer science and numerical techniques,numerical simulation has become an important tool to study the evolution of solidified microstructure.Because in the case of establishing the correct mathematical and physical model,the computer has a powerful computational force,which can be used to calculate the evolution process of grain during solidification.Therefore,as a supplement to the experiment,the numerical simulation is very good in this respect,because the dynamic evolution has been studied and explained,which can well reproduce the evolution of the metal structure during the solidification process.So that researchers have a better understanding of the solidification process,so as to produce a better casting process design.In this paper,the relevant processes of eutectic reaction stage of gray cast iron were simulated by establishing a set of cellular automata simulation software based on the theoretical basis,the experimental platform was Visual Studio 2015 MFC platform,and the computer programming language was C++.The model defines different growth modes of graphite and austenite,and establishes the transition rules among different cells and the diffusion rules among different cells.The microscopic solidification evolution and growth model of eutectic aggregates of gray cast iron was established.In this paper,the eutectic growth model of gray cast iron cellular automata is established.Firstly,the diamond interface capture rules of key graphite cellular automata model are established according to the crystal structure of graphite and the metallographic structure obtained in experiments.The microscopic solidification evolution growth model of flake graphite was determined,and the cross precipitation model and the austenite microscopic solidification evolution growth model were combined to realize the cross precipitation growth of graphite and austenite.Thus,the co-growth of graphite and austenite in eutectic grains in liquid phase was completed.The changes of eutectic grains were observed by changing different cooling rates in the simulation.The eutectic morphologies of gray cast iron with different cooling rates were obtained due to the different wall thickness of the stepped castings.The morphology of graphite with different cooling rates was explained experimentally.In this paper,a multi-core eutectic growth model is established on the basis of the micro-solidification evolution and growth model of a single gray cast iron eutectic,and the competitive relationship between eutectic grains is analyzed,and the morphology of graphite is more prone to bending and bifurcation under the condition of multi-core.Under multiple core and graphite distribution more uniform,analyzes the core type B in the graphite graphite under more more reason,eutectic growth of graphite and austenite behavior in solidification evolution and change,the analysis of the inoculant Si of graphite formation in actual effect,from the model on the basis of explaining the inoculants in under the action of eutectic graphite morphology in the cause of the change.The multi-core model reasonably reproduces the competitive growth behavior of eutectic grains and the change of morphology of graphite in the contact area of eutectic grains.