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

TL;DR

This study investigates the formation of Nb-rich droplets and microstructures in laser-deposited Ni-Nb alloys through experiments and simulations, revealing how cooling rates and composition influence phase formation and microstructure features.

Contribution

It combines experimental observations with finite element and phase-field simulations to understand microstructure formation in Ni-Nb alloys during laser deposition.

Findings

Cell and droplet spacings follow a power law with cooling rate.

Laves phase forms at a critical Nb composition in droplets.

Anisotropy affects the Laves phase fraction significantly.

Abstract

Ni-rich $\gamma$ cells and Nb-rich eutectic droplets that form during laser power bed fusion solidification of Ni-Nb alloys are studied using experiments and simulations. Finite element simulations estimate the cooling rates in the melt pool and phase-field simulations predict the resulting cellular microstructures. The cell and droplet spacings are determined 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. Finally, our simulations demonstrate that anisotropy in the $\gamma$ orientation influences the Laves fraction significantly.