5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Solidification microstructure of metal castings determines their as-cast mechanical properties. Accurate prediction of as-cast grain structure and key defects (such as porosity) is critical in the design and manufacturing of metal castings using an integrated computational materials engineering (ICME) approach. In this talk, a three-dimensional (3-D) model based on cellular automaton (CA) and process simulation will be presented for predicting grain growth coupled with hydrogen porosity evolution during solidification of aluminum alloys in high pressure die casting (HPDC). The 3-D CA model integrates the concurrent nucleation and growth of grains as well as those of hydrogen porosities. The diffusions of both solute and hydrogen are considered in the model. A test specimen casting, consisting of different wall thicknesses, was simulated using a finite element based software ProCAST®. The thermal history of the simulated casting was extracted and used in subsequent mesoscale CA modeling to simulate the evolution of microstructure during HPDC. The grain morphology, grain density and grain size were obtained, and the porosity size and distribution were computed by CA modeling. The effects of cooling rates on final grain size and percentage of porosity were discussed. Electron backscatter diffraction (EBSD) analysis was performed on different wall thicknesses samples to validate the simulated results of grain size and distribution. X-ray micro computed tomography (microCT) technique was used to characterize the porosity morphology and distribution qualitatively and quantitatively. The 3-D simulated microstructure results, including grains and porosities, are in excellent agreement with the experimental results, which means the present model can be used in ICME design and development of aluminum castings.