Simulation Of Solidification Structure Of Mg-Y-Zn-Mn-Ca Alloy By CAFE Method

The solidification process of the alloy has an significant effect on the solidification structure and properties of the castings.Therefore,it is effective to research and control the solidification process of the alloy to improve the solidification structure and macroscopic defects.Since the solidification process of the alloy is a complex and opaque process,it is very hard to analyze the solidification process accurately.In the past,the solidification process depend on experimental method which is based on experience.It not only wastes a lot of manpower and financial resources,but also increases the experimental cycle,so the use of computer technology in the alloy solidification process simulation has been fully developed.Through the computer simulation can simulate the change of each field in the process of casting,can more intuitively analyze the solidification process of the alloy,so as to obtain more reasonable process parameters,greatly reducing the cost and the experimental period.The solidification structure of different kinds of steel,aluminum alloy and small part of magnesium alloy was simulated by CAFE method in the world.The results were in good agreement with the experimental results.However,there are few reports on the solidification structure of Mg-Y-Zn-Mn-Ca alloy.In this paper,Pro CAST software was used to select the interface heat transfer coefficient and boundary condition suitable for the model.The solidification process of Mg-Y-Zn-Mn-Ca alloy was simulated.The simulation conditions were in good agreement with the experimental conditions.The temperature field and flow field during the solidification of the alloy were studied,and the solidification regularity of the alloy was analyzed.At the same time,the shrinkage of the alloy during the solidification process were simulated.The macroscopic defects of the alloy were improved by designing the reasonable mold and selecting the appropriate temperature.The microstructure of Mg-Y-Zn-Mn-Ca alloy was studied by CAFE method.The nucleation parameters of the model were determined by combining with the experiment.The effects of nucleation parameters,casting temperature,mold material and Ca element on the solidification structure of the alloy were studied.The results show that when the casting temperature is 730 ℃,the height of the casting riser is 40mm and the inner diameter is 56mm,the shrinkage of the castings are improved and the performance of the castings is improved.When the nucleation parameters are ΔT_v,man = 10K、Δ_Tv,σ=1,n_v,max =2×10¹³ m^-3,the simulated grain size is about 32.25 μm,the experimental grain size is about 29.76μm.The experimental results are in good agreement with the simulation results.The nucleation parameters have an important effect on the solidification structure of the alloy.With the increase of the Δ_Tv,max and decrease of the nv,max,the grain size increases obviously.With the increase of the Δ_Tv,σ,the large grain area increases obviously.With the increase of pouring temperature,the columnar crystal area in the solidified structure of the alloy increases,and the grain size increases obviously.The use of cooling capacity of 45#steel mold can be uniform and fine equiaxed grains,when use of sand mold,the grain size increased significantly.The addition of Ca element effectively modifies the solidification structure of the alloy,which increases the nucleation of heterogeneous nuclei,and reduce the dendritic growth kinetics coefficient.