Numerical Simulation Of Centrifugal Investment Casting Of Large Thin-wall Complex Ti-6Al-4V Castings

Recently,the prosperous aerospace industry has led growing demands for shapecomplicated large thin-wall titanium alloy structural components.Investment casting is widely used in producing those components,for it facilitates both shape-complicated castings and improving the filling capacity by centrifugal casting.Therefore,the numerical simulation of centrifugal investment casting for large thin-wall titanium alloy structural components is of great significance in academics and productions as well.The investment casting process of Ti-6Al-4V(Ti64)alloy got studied.Firstly,a 1-D heat transfer model got established based on the phenomenon of heat transfer during the investment casting of Ti64 alloy.Using the thermal conduction inverse algorithm,the interfacial heat transfer coefficients(IHTCs)between the titanium alloy casting and the mold of different materials got calculated,and the potential influence of the parameter errors to the accuracy of inverse calculation also got assessed.Then,to identify the accuracy of the IHTCs,the IHTCs were applied in a 3-D model to simulate the temperature field during the solidification and cooling process of the investment casting,and the results showed the predicted results agreed well with the actually measured ones.During the numerical simulation of large thin-wall components under centrifugal investment casting,three methods-weakly compressible model(WCM),ununiformed finite difference mesh(UFDM)and memory management of active elements(MMAE)-got developed to reduce the memory consumption and ensure the simulation efficiency.The UFDM and MMAE significantly cut down the number of grids and improved memory usage efficiency.The precision of WCM and UFDM were verified by simulation of cavity heat convection in a square cavity.Accompanied with the IHTCs,a simulation model got developed and used to simulate the actual components produced by centrifugal casting.The predicted shrinkage formation was consistent with the experiment results.By CA method,a nucleation and growth model for the microstructure evolution during solidification and solid phase transformation process of Ti64 alloy got established.Firstly,the nucleation and growth of β grains during the solidification process got simulated and the results agreed well with the experiments.Then,for the α plates in solid phase transformation process of Ti64 during investment casting,growth models of the edge growth velocity and thickness growth rate were established.The influences of the competitive growth of α plates and the latent heat release during the solid phase transformation process on the cooling rate of the components were assessd in the simulation.The simulated thickness and morphology of α plates matched well with the actual experiment.For the centrifugal investment casting of a door frame casting and a casing casting,the filling and solidification processes got simulated and the potential shrinkages were obtained through the simulation,which provided a reference for the optimization of the casting process.