Formation of Nb-rich droplets in laser deposited Ni-matrix microstructures

Published: March 15, 2018

Author(s)

Supriyo Ghosh, Mark R. Stoudt, Lyle E. Levine, Jonathan E. Guyer

Abstract

Ni-rich $\gamma$ cells/dendrites and Nb-rich eutectic droplets that form during laser power bed fusion (LPBF) solidification of Ni-Nb alloys are studied in the present work using numerical simulations. Finite element simulations estimate the local cooling rates in the LPBF melt pool and phase-field simulations predict the resulting cellular microstructures. The cell and droplet spacings are extracted from the simulated microstructures as a function of cooling rate and fit to a power law. The formation of Laves phase is predicted for a critical composition of Nb in the liquid droplets. We find that the cell/droplet spacing as well as the Laves fraction decrease with increasing cooling rate. Our simulations show that the orientation of the primary $\gamma$ phase influences the Laves fraction. The simulated microstructures are supported by preliminary experimental observations of the as-deposited microstructures.
Citation: Scripta Materialia
Volume: 146
Pub Type: Journals

Keywords

Additive manufacturing, Finite element, Phase-field, Cells, Droplets, Laves phase
Created March 15, 2018, Updated September 06, 2018