abstract
- Cellular or dendritic microstructures that result as a function of additive manufacturing solidification conditions in a Ni-based melt pool are simulated in the present work using three-dimensional phase-field simulations. A macroscopic thermal model is used to obtain the temperature gradient G and the solidification velocity V which are provided as inputs to the phase-field model. We extract the cell spacings, cell core compositions, and cell tip as well as mushy zone temperatures from the simulated microstructures as a function of V. Cell spacings are compared with different scaling laws that correlate to the solidification conditions and approximated by G-mV-n. Cell core compositions are compared with the analytical solutions of a dendrite growth theory and found to be in good agreement. Through analysis of the mushy zone, we extract a characteristic bridging plane, where the primary γ phase coalesces across the intercellular liquid channels at a γ fraction between 0.6 and 0.7. The temperature and the γ fraction in this plane are found to decrease with increasing V. The simulated microstructural features are significant as they can be used as inputs for the simulation of subsequent heat treatment processes.