Numerical Simulation For Primary Phase Precipitation Procession Of Al-Si-Cu Alloy

Al-7wt%Si-5wt%Cu ternary alloy has been used widely in aviation/astronavigation, motorcycle/automotive industry,construction industry and so on for its high specific tenacity,good absorption of vibration and electromagnetic shielding.As we know,final properties of casting material depend on solidification structure.Therefore,it is a key point of mastering the structure forming process for later controlling structure.Using computer simulating technique,the nucleation process,grain growth,microstructure evolution and grain degree can be reappeared during solidification process.Furthermore,the prefect microstructure and mechanical properties can be got by adjusting the solidification processing parameters.That is to say,simulating microstructure play a bridge role in connecting processing design and controlling properties.It is important for connecting processing,structure and properties together.In this paper,a mathematical model of primary phase structure of Al-Si-Cu ternary alloy was founded by using cellular automaton method,which included temperature field model,latent heat releasing model,nucleating model,grain growth model and solute diffusing model.Then,using the model,temperature field and primary phase precipitation process were simulated.Finally,relationship among the solid fraction,interface curvature, solute concentration,grain growth velocity,solidification time and solid fraction.The simulated results of temperature field and primary phase morphology were consisted with experimental results well,which indicated that the mathematical model was reasonable.The simulated results shows:the primary phase morphology approaches to global under sand molding and metal molding condition;the primary phase of metal molding is much finer than that of sand molding under the same pouring temperature;in a single cell unit,the curvature of solid/liquid decreases as solid fraction increases;in a single cell unit,the total solute concentration decreases and the solute concentration in the liquid phase increase gradually as solid fraction increases due to solute diffusing effect;in a single cell unit,the total undercooling degree increases as solid fraction increases,so the growth velocity of crystal increases gradually.