Yang, Mingzhang2026-05-292026-05-292026-05-292026-05-20https://hdl.handle.net/10012/23439Sinter-based additive manufacturing (SBAM) has emerged as a promising route for net-shape production of metallic components. These processes decouple shaping from densification, enabling high build rates and batch-type thermal processing for high-throughput manufacturing. However, their broader adoption remains limited by challenges in achieving full densification, while maintaining geometrical fidelity, as well as the reliance on high-cost, highly refined feedstocks. This dissertation employed multiple sinter-based additive manufacturing routes, including binder jetting, MoldJet printing (paste-based additive manufacturing), and gel-casting, to systematically investigate densification and deformation behavior across a range of steel feedstocks. These include conventional atomized pre-alloyed powders, non-refined pre-alloyed powders, and pre-mixed oxide precursors. A combination of characterization techniques, including microscopy, thermal analysis, compositional analysis, and thermodynamic calculations, was used to elucidate the governing mechanisms of densification, phase evolution, and deformation during sintering. For pre-alloy powder systems with low as-printed density, it was established that solid-state sintering alone was insufficient for densification and that supersolidus liquid phase sintering (SLPS) can be leveraged to attain high final density. Deformation was found to be governed by pore structure evolution prior to liquid formation and mitigated through modified heating profiles. An inherent trade-off was identified between achieving near-full density and retaining fine features. A processing window was subsequently established to balance densification and geometrical fidelity. To address the complexity of sintering shrinkage under phase transformations, a phenomenological modeling framework based on continuum sintering theory was developed. By incorporating multi-stage kinetics and a variable bulk modulus, the model captures densification behavior under varying heating rates and phase evolution, providing improved predictive capability for shrinkage compared with conventional approaches. Lastly, to achieve densification and shape control while reducing material cost, this dissertation investigated the utilization of chemically non-refined powder system in SBAM. Un-annealed water-atomized powders with high carbon and oxygen contents were shown to be directly processable through in-situ chemical refinement during sintering. In addition, mixed ore-derived oxides (metal precursors) were transformed into dense metallic components with 316 stainless steel composition via H2-driven redox reactions during sintering, enabling rapid densification at reduced temperatures without macroscopic deformation. The sequential oxide reduction and alloying within the mixed system are rationalized through thermodynamic analysis, establishing a pathway for designing oxide precursor compositions as alloying sources. Collectively, these results demonstrate that densification, geometrical control, and feedstock cost reduction can be addressed simultaneously, broadening the manufacturing and materials design space of SBAM.enAdditive ManufacturingSinteringGreen steelBinder jettingPowder metallurgySustainable manufacturingMetal OxideDoctoral Thesis