Influence of binder compositions, solvents, and material extrusion parameters on aluminum additive manufacturing via SDS

Margarete Hufnagl

Research output: ThesisMaster's Thesis

Abstract

Material extrusion (MEX) is an additive manufacturing technique that can serve as the shaping step to create green parts, in the shape, debinding, and sintering (SDS) process of metal specimens. Employing SDS with MEX for aluminum offers a promising cost-effective production method for parts with complex geometry. However, this process requires a highly filled thermoplastic binder system for AlSi1 powder, to produce filament for the MEX process. The filament is needed to feed the 3D printer with the material required to shape the specimens. An important challenge in utilizing MEX in SDS is the development of an appropriate binder composition that meets the requirements for the printing step as well as the debinding and sintering step. For the printing step, the filaments should be a combination of the following characteristics - tough, flexible and low viscous. The debinding step requires a dual-component binder system, where one component is soluble in the chosen solvent, while the other one is resistant to this solvent. The solvents evaluated in this master thesis are cyclohexane, acetone, and water. Additionally, the binder components should posses a lower thermal degradation temperature than the sintering temperature of aluminium. This is particularly challenging since the AlSi1 sintering temperature is similar to the degradation temperature of most thermoplast degrade. This is important because the binder must be completely removed to reduce the risk of high levels of residual oxygen and carbon, as well as the formation of Al2O3, which can significantly affect the quality of the sintered part. The objective of the master thesis, conducted as part of the project ALF³, was to enhance the understanding of the binder components required for this specific process. Therefore the impact of various backbone materials as a binder component, along with the influence of several main binder materials on the rheological, thermal, printing, and debinding properties of the AlSi1 feedstocks were analyzed. The thermal properties of the binder systems and feedstocks were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) testing. The rheological behavior was examined using high-pressure capillary rheometers. Additionally, the contact angle measurements were performed to see the effect on the wetting behavior of the binder components and the particle distribution of AlSi1 in the Feedstock. This was followed by the production of feedstock filaments, analysis with scanning electron microscopy (SEM) and MEX printing. The findings demonstrated the possibility of producing three optimized binder formulations for each solvent employed in the debinding process. Moreover, there is potential to refine the printing process to meet the specific demands of highly packed filaments with a volume fraction of 55 vol.%.
Translated title of the contributionEinfluss von Binderzusammensetzungen, Lösungsmitteln und Materialextrusionsparametern auf die additive Herstellung von Aluminium mittels SDS
Original languageEnglish
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Holzer, Clemens, Supervisor (internal)
Award date28 Jun 2024
Publication statusPublished - 2024

Bibliographical note

no embargo

Keywords

  • aluminum additive manufacturing
  • Material Extrusion
  • MEX
  • Shaping Debinding Sintering
  • SDS
  • binder development

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