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@PHDTHESIS{Nachtsheim:1020004,
author = {Nachtsheim, Julia Alessandra},
othercontributors = {Markert, Bernd and Stoffel, Marcus},
title = {{I}n vitro corrosion behaviour of biodegradable magnesium
implants},
volume = {25},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-08712, 25},
series = {Report. Institute of General Mechanics / Institut für
Allgemeine Mechanik (IAM)},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2025},
abstract = {Biodegradable magnesium implants can potentially resolve
major challenges of conventional implant technologies. They
provide mechanical support to the fracture site and
gradually degrade within the body. This can eliminate the
need for an implant-removal surgery, which is beneficial to
the patient and to healthcare systems. Magnesium alloys are
especially suitable for bone fracture treatments, as they
are highly biocompatible and possess mechanical properties
similar to those of native bone. Their similar elastic
moduli improves load transfer. Thereby, the recovering bone
is continuously subjected to physiological stresses. This
reduces the risk of stress-shielding and pathological tissue
development. Their broad application, however, is limited by
their fast material degradation in physiological conditions,
which can cause harmful side effects and can result in
catastrophic implant failure. In this context, research and
development efforts are required to establish in-depth
understanding of the relevant degradation processes and to
derive strategies to overcome these limitations. The aim of
this thesis is to systematically study the in vitro
corrosion behaviour of a biodegradable magnesium alloy WE43,
which is currently under development for load-bearing
implant applications. The material is alloyed with
rare-earth elements, and a PEO coating is applied for an
improved protection against corrosion. For this purpose,
experimental in vitro studies were conducted to assess the
degradation behaviour of the material under different
external load protocols. In service conditions, the implant
is exposed to considerable mechanical loadings and
aggressive physiological corrosion environments. This
combination triggers adverse mechano-chemical interactions,
which accelerate material degradation. Hence, understanding
the underlying mechanisms is particularly important. The
experimental results reveal a localised corrosion process of
WE43, which can be attributed to the fine and evenly
dispersed secondary phases. The barrier effect of the
coating fully preserves the mechanical integrity for 14 days
and delays the degradation process for longer periods. Under
constant loadings, a critical stress level is identified,
which leads to a high probability of failure in the short
term. The protection of the coating against material
degradation is limited to its undamaged state. High local
stresses trigger coating damage, which adds another source
for material failure. Under very slow and continuously
increasing straining in slow strain rate testing, the
material suffered significant embrittlement. Synergetic
mechanisms of corrosion and crack propagation are revealed
on fracture surfaces. In corrosion-fatigue experiments, the
fatigue performance is considerably reduced and the failure
mode changes in comparison to the pristine alloy. The
experimental findings provide valuable information on the
environmentally assisted mechanisms. Based on the
experimental results, strategies for further improving the
material’s functionality are derived and some findings can
be translated into recommendations for therapeutic
strategies.},
cin = {411110},
ddc = {620},
cid = {$I:(DE-82)411110_20140620$},
pnm = {RePlaSys - KMU-Innovativ - Verbundprojekt: Resorbierbares
Plattensystem aus Magnesium für die Trauma- und
Unfallchirurgie (RePlaSys) (BMBF-13GW0352B)},
pid = {G:(DE-82)BMBF-13GW0352B},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2025-08712},
url = {https://publications.rwth-aachen.de/record/1020004},
}
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