This work examines how feedstock composition and process settings influence the performance of Al-6061 parts made through material extrusion (MEX). A feedstock with 57 vol% (78 wt%) solids loading was selected based on torque rheometry, showing stable flow and shear-thinning behavior with a measured viscosity of 710.9 ± 3.2 Pa·s. Filaments produced from this material had a consistent diameter of 1.74 ± 0.0064 mm and were used to print specimens at extrusion multipliers of 0.9, 0.95, and 1.0. Debinding and sintering procedures, guided by thermal analysis, resulted in a peak density over 97% of the theoretical value. Among the conditions tested, the 0.95 extrusion multiplier produced the most favorable mechanical properties, with an ultimate tensile strength of 153.5 ± 3 MPa, a yield strength of 68.2 ± 11.7 MPa, and elongation reaching 28 ± 3%, which aligns with values reported for annealed Al-6061. Fractographic analysis showed a ductile fracture mode, confirming good interlayer adhesion and consistent sintering. These results show that MEX is a reliable method for fabricating Al-6061 parts with complex geometries and stable mechanical performance.

3D printing pure copper with high electrical conductivity and exceptional density has long been challenging. While laser-based additive manufacturing technologies suffered due to copper's highly reflective nature towards laser beams, parts printed via binder-assisted technologies failed to reach over 90% IACS (International Annealed Copper Standard), electrical conductivity. Although promising techniques such as binder jetting, filament, and pellet-based 3D printing that can print copper exist, they however still face difficulties in achieving both high sintered densities and electrical conductivity values. This is due to a lack of comprehensive understanding of property evolution from green to sintered states and the strategies that can be used to enhance the density and electrical properties of Sinter-Based Material Extrusion (MEX) 3D printed copper parts. This dissertation presents an in-depth investigation into the advancements and challenges of 3D printing pure copper, specifically focusing on Material Extrusion (MEX) processes. It emphasizes the viability of bound powder copper feedstocks for Material Extrusion 3D printing. It highlights the importance of achieving 100% density in the green vi stage to ensure over 93% sintered density and 98% Hot Isostatic Pressing (HIP) density. The study delves into the difficulties of 3D printing, sintering, and Hot Isostatic Pressing (HIP) of copper parts, addressing the gap in understanding the scaling of mechanical and electrical properties from the green to the sintered state in the MEX metal 3D printing process. The insights and knowledge gained from this section are then utilized to improve the thermal performance of bound metal MEX 3D printed copper heat sinks. This research explores the uncharted territory of lattice structures for heat sinks, investigating three types of lattice structures through experimental analysis and simulations to explore the potential advantages of lattice structure-based bound metal MEX 3D printing for fabricating high-performance copper heat sinks. Finally, the research focuses on understanding the intricate interplay of material viscosity, mechanical properties, and printing speed in bound-powder-polymer MEX 3D printing. Exploring PLA, TPU, and bronze-filled metal powder-bound filaments, the study investigates their impact on achieving a printed part density of 100±5%. Process maps of density and viscosity were created for each material type, and a full factorial design of experiments was conducted to identify the effects of print conditions on various variables. This section provides crucial insights into the 3D printing process of polymer filaments, offering guidance for new material design and discovery for bound metal filaments. Overall, this dissertation contributes to understanding the challenges