Numerical simulation on directional solidification process of DD6 single crystal superalloy thin-walled specimen

For the difficulty in preparation of thin-walled specimen of DD6 single crystal superalloy, the finite element model of thin-walled slab specimen was established to simulate the directional solidification process of investment casting thin-walled slab specimen using a numerical simulation software ProCAST. The effects of specimen shape and solidification parameters on temperature field, temperature gradient field and mushy zone were investigated. The results show that temperature gradient at the working end of the thin-walled slab specimen's centre location ranges from 60℃/cm to 65℃/cm. The solidus isotherm of mushy zone is relatively flat, but liquidus isotherm closed to furnace wall is slightly lower than that far away from furnace wall. Geometrical shape has great effect on the directional solidification process of single crystal superalloy specimen. Increasing the pouring temperature or decreasing the withdrawal rate helps to increase the temperature gradient in solid/liquid interface front and reduce the mushy zone width. The numerical simulation results of the directional solidification are consistent with that of the actual casting results. The solidification simulation can provide the technical support for the preparation of thin-walled specimen.