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%0 Thesis
%A Kürnsteiner, Philipp
%T Precipitation reactions during the intrinsic heat treatment of laser additive manufacturing
%I Rheinisch-Westfälische Technische Hochschule Aachen
%V Dissertation
%C Aachen
%M RWTH-2019-11831
%P 1 Online-Ressource (141 Seiten) : Illustrationen, Diagramme
%D 2019
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2020
%Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019
%X Laser additive manufacturing (LAM) allows to produce complex and highly customized metallic parts from a computer aided design file (CAD) by melting metallic powder with a focused laser beam. The inherent geometrical design freedom this technique offers enables tremendous weight savings and parts with a complexity that would be impossible to achieve by conventional manufacturing techniques. However, many alloys face problems of either poor processability in LAM or insufficient strength. Even those alloys that are well processable, often do not exploit the full potential of LAM processes as they were typically designed and optimized for conventional processing routes. This work aims at designing new alloys custom-tailored to LAM processes making use of some unique features of these processes. For example, the cyclic re-heating occurring during the process, the so called intrinsic heat treatment (IHT), is used to trigger precipitation reactions already during the process avoiding an aging heat treatment for precipitation strengthened materials. Furthermore, the potential of triggering phase transformations in conventional alloys used in LAM is evaluated and LAM-produced and conventionally-produced parts are compared. The complex microstructures of all samples are characterized at different length scales ranging from cm to nm by light optical microscopy (LOM), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and atom probe tomography (APT). After showing that during the IHT of a directed energy deposition (DED) processing of a conventional 18Ni-300 Maraging steel slight clustering occurs, simple ternary Fe-Ni-Al and Fe-Ni-Ti steels are developed that respond very well to the in-situ strengthening approach using the IHT. Rapid alloy prototyping approaches using compositionally graded samples are used to efficiently screen a large variation in compositions and find the optimal ones that show the desired microstructure and a strong response to the IHT. In an Fe17Ni10Al (at
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2019-11831
%U https://publications.rwth-aachen.de/record/774875