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Numerical study of epitaxial growth after partial remelting during selective electron beam melting in the context of Ni–Al

H. J. Schaar, I. Steinbach, M. Tegeler.

Metals, 11, 2012, (2021)

Left: Microstructure evolution and the corresponding Al concentration distribution during solidification in context of the selective electron beam melting process for different time steps (a = 0.0008 s, b = 0.0018 s, c = 0.0026 s, d = 0.09 s); on the right hand side is a magnification of the primary γ‘ particles. Right: Plot of the averaged (avg.) system temperature and the amount of released latent heat over the simulation time with a magnification of the effect of recalescence.

Abstract
In the selective electron beam melting approach an electron beam is used to partially melt the material powder. Based on the local high energy input, the solidification conditions and likewise the microstructures strongly deviate from conventional investment casting processes. The repeated energy input into the material during processing leads to the partial remelting of the already existing microstructure. To closer investigative this effect of partial remelting, in the present work the phase-field model is applied. In the first part the solidification of the referenced Ni–Al system is simulated in respect to selective electron beam melting. The model is calibrated such to reproduce the solidification kinetics of the superalloy CMSX-4. By comparison to experimental observations reported in the literature, the model is validated and is subsequently applied to study the effect of partial remelting. In the numerical approach the microstructures obtained from the solidification simulations are taken as starting condition. By systematically varying the temperature of the liquid built layer, the effect of remelting on the existing microstructure can be investigated. Based on these results, the experimental processing can be optimized further to produce parts with significantly more homogenous element distributions.


Keyword(s): nickel alloy; phase-field model; electron beam methods; directional solidification; microstructure
Cite as: https://www.mdpi.com/2075-4701/11/12/2012/htm
DOI: 10.3390/met11122012
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