New Grain Formation Mechanisms during Powder Bed Fusion

Language
en
Document Type
Article
Issue Date
2021-07-06
First published
2021-06-16
Issue Year
2021
Authors
Rausch, Alexander M.
Pistor, Julian
Breuning, Christoph
Markl, Matthias
Körner, Carolin
Editor
Publisher
MDPI
Abstract

Tailoring the mechanical properties of parts by influencing the solidification conditions is a key topic of powder bed fusion. Depending on the application, single crystalline, columnar, or equiaxed microstructures are desirable. To produce single crystals or equiaxed microstructures, the control of nucleation is of outstanding importance. Either it should be avoided or provoked. There are also applications, such as turbine blades, where both microstructures at different locations are required. Here, we investigate nucleation at the melt-pool border during the remelting of CMSX-4® samples built using powder bed fusion. We studied the difference between remelting as-built and homogenized microstructures. We identified two new mechanisms that led to grain formation at the beginning of solidification. Both mechanisms involved a change in the solidification microstructure from the former remelted and newly forming material. For the as-built samples, a discrepancy between the former and new dendrite arm spacing led to increased interdentritic undercooling at the beginning of solidification. For the heat-treated samples, the collapse of a planar front led to new grains. To identify these mechanisms, we conducted experimental and numerical investigations. The identification of such mechanisms during powder bed fusion is a fundamental prerequisite to controlling the solidification conditions to produce single crystalline and equiaxed microstructures.

Journal Title
Materials
Volume
14
Issue
12
Citation
Materials 14.12 (2021): 3324. <https://www.mdpi.com/1996-1944/14/12/3324>
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