Simulation and analysis of γ-Ni cellular growth during laser powder deposition of Ni-based superalloys

Published

March 1, 2018

Author(s)

Supriyo Ghosh, Nana Ofori Opoku, Jonathan E. Guyer

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 $G^{-m}V^{-n}$. 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 $\gamma$ phase coalesces with the intercellular liquid channels at a $\gamma$ fraction between 0.6 and 0.7. The temperature and the $\gamma$ 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.

Citation

Acta Materialia

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.commatsci.2017.12.037

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Keywords

phase-field, cells, microsegregation, mushy zone, coalescence

Citation

Ghosh, S. , Ofori, N. and Guyer, J. (2018), Simulation and analysis of γ-Ni cellular growth during laser powder deposition of Ni-based superalloys, Acta Materialia, [online], https://doi.org/10.1016/j.commatsci.2017.12.037 (Accessed December 11, 2024)