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@PHDTHESIS{Roth:1009108,
author = {Roth, Jan-Philipp},
othercontributors = {Krupp, Ulrich and Jahns, Katrin and Kruml, Tomáš},
title = {{L}aser powder bed fusion of dispersion strengthened alloy
400},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-03342},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2025, Kumulative Dissertation},
abstract = {Additive manufacturing (AM) evolved rapidly during the last
decades. Other than conventional manufacturing (CM), this
technology allows for near-net-shape components, barely
being limited by geometrical constraints. Revealing very
fine grains, that, in turn, consist of cellular
nanostructures, the resulting performance of such components
differentiates significantly from CM. Continuous research is
thus required to fully understand this comparably young
manufacturing technology. Hence, the first pillar of this
work is considering the manufacturing. Besides AM, the
modification of base alloy systems via the concept of
dispersion strengthening (DS) has attracted great attention
in recent years. The implementation of nanoscaled ceramics
into the lattice of the alloy results in so-called metal
matrix nanocomposites (MMNC). This material class shows
clearly improved mechanical properties, mainly being linked
to the successful suppression of dislocation movements.
Being dependent on a complex multitude of factors, efficient
DS requires considerably more fundamental studies to
generate a complete picture. Therefore, this thesis also
deals with the mechanism.Thirdly, among the wide variety of
material classes used in high-performance industries,
NiCu-based alloys enable essential products like heat
exchangers, pumps, and valves in key sectors like maritime,
energy, and chemistry. A prominent representant of this
material category is Alloy 400. However, barely any
knowledge is available on this alloy when manufactured
additively, restricting its potential application.
Consequently, the material is covered in this thesis as
well. Combining these subject areas, this thesis establishes
holistic process routes for Laser Powder Bed Fusion of
Dispersion Strengthened Alloy 400 variants. It is documented
how to generate powder feedstocks for laser beam powder bed
fusion of metals (PBF-LB/M) via gas atomization of Alloy 400
and the peculiarities of powders and parts are disclosed.
Copper segregations on both grain boundaries and cell walls
such as high dislocation densities throughout the micro
dendritic structure were found. Due to the overall finer
grain structure of the AM variant, tensile properties
increased, and elongation lowered compared to CM. Based on
the findings of unmodified standard Alloy 400, two
successful DS modification routes were elaborated for the
present alloy. The first one is based on a gas atomization
reaction synthesis (GARS) principle. The feasibility of
nanoparticle formation in situ during atomization due to
reaction of the atomization gas with the melt was
demonstrated. The ceramics were identified as TiN and they
successfully limited dislocation movement throughout the
matrix via pinning. This resulted in considerably improved
mechanical properties compared to the standard PBF-LB/M
variant. The second modification approach applied an ex situ
powder modification in a fluidized bed reactor (FBR).
Enabled by nitrogen diffusion, a high number of TiN was
generated in powders which was again significantly increased
after AM, allowing for outstanding tensile, creep, and
fatigue performance.Therefore, several alloy systems have
been developed and qualified for use in AM while enabling
outstanding properties.},
cin = {522110 / 520000},
ddc = {620},
cid = {$I:(DE-82)522110_20180901$ / $I:(DE-82)520000_20140620$},
pnm = {topAM - Tailoring ODS materials processing routes for
additive manufacturing of high temperature devices for
aggressive environments (958192)},
pid = {G:(EU-Grant)958192},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-03342},
url = {https://publications.rwth-aachen.de/record/1009108},
}
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