Date on Master's Thesis/Doctoral Dissertation

8-2025

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Kate, Kunal H

Committee Co-Chair (if applicable)

Atre, Sundar V

Committee Member

Wang, Hui

Committee Member

Satyavolu, Jagannadh

Author's Keywords

Aluminum additive manufacturing; material extrusion (MEX); post-processing; mechanical properties; microstructure; density

Abstract

Material extrusion (MEX) additive manufacturing presents a promising pathway for producing metal components with complex geometries while avoiding the safety hazards associated with loose powder handling in conventional metal additive manufacturing processes. This dissertation investigates the development and optimization of MEX processes for aluminum alloys, addressing critical challenges in feedstock formulation, printing parameter optimization, and post-processing strategies. Three distinct approaches were explored to advance the capabilities of aluminum MEX: filament-based processing of 6061 aluminum, paste-based extrusion of 6061 aluminum, and development of a novel aluminum-magnesium-tin alloy system for space manufacturing applications. The filament-based approach successfully demonstrated the production of 6061 aluminum components achieving 97.1% theoretical density after sintering. Through systematic optimization of solids loading at 57 vol%, binder formulation, and processing parameters, mechanical properties comparable to annealed 6061-O aluminum were obtained, with ultimate tensile strength of 153.5 MPa and 28% elongation. The paste-based methodology enabled processing at lower extrusion pressures (10 psi) while achieving 96.3% density, demonstrating the potential for energy-efficient manufacturing scenarios. A multi-stage thermal debinding protocol was developed based on thermogravimetric analysis, ensuring complete binder removal without introducing defects. The investigation of aluminum-magnesium-tin alloys revealed unique challenges associated with pure aluminum processing, including poor powder flowability and heterogeneous microstructures. Despite achieving moderate densification (81.4%), compositional analysis revealed significant oxidation at fracture surfaces, highlighting the need for atmosphere optimization during processing. This work establishes fundamental understanding of the relationships between powder characteristics, feedstock rheology, processing parameters, and final part properties in aluminum MEX. The findings provide essential guidelines for advancing aluminum additive manufacturing technologies, particularly for applications requiring safe powder handling and sustainable manufacturing approaches in terrestrial and space environments.

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