Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Automotive Engineering
Committee Chair/Advisor
Dr. Shunyu Liu
Committee Member
Dr. Laine Mears
Committee Member
Dr. Rahul Rai
Committee Member
Dr. Garrett Pataky
Abstract
Additive Manufacturing (AM) has revolutionized the production of high-performance materials by enabling unprecedented opportunities for customization, efficiency, and material innovation. Alongside these advantages, AM processes introduce unique thermal features such as rapid cooling rates and steep thermal gradients, which drive the formation of distinctive microstructural features and enhanced mechanical properties. However, these features also pose challenges, including mechanical anisotropy, unstable interfacial behavior, and metallurgical defects. This dissertation addresses these challenges, as they critically influence the performance and reliability of AM components, key factors for the widespread adoption of AM in automotive, aerospace, energy, and defense applications.
The first study investigates “mechanical anisotropy” in 316L stainless steel (316L-SS) fabricated by laser powder bed fusion (LPBF). While 316L-SS is widely valued for its corrosion and oxidation resistance, the inherent mechanical anisotropy arising from build orientations (BOs) and scan rotation angles (SRAs) limits its use in structural applications. Tensile testing confirmed significant anisotropy across different BOs and SRAs. Multi-scale characterization identified dislocation density variations as the dominant contributor, with crystallographic texture as a secondary factor. These findings informed the development of a crystal plasticity (CP) model, where representative volume elements generated in Dream.3D were simulated using the DAMASK framework to successfully predict mechanical anisotropy.
The second study focuses on “interfacial properties” of iron (Fe)-based metal matrix composites (MMCs) fabricated by laser-directed energy deposition (LDED). The stability of the metal–ceramic interface was examined for reinforcements including silicon carbide (SiC), titanium carbide (TiC), zirconium carbide (ZrC), and tungsten carbide (WC). High-resolution electron microscopy revealed that SiC undergoes complete dissociation, forming pure carbon precipitates and Fe–Si–C solid solutions, thereby demonstrating instability during processing. TiC exhibited the highest interfacial stability with minimal dissociation, while ZrC showed moderate stability but generated nanoscale resolidified precipitates across the matrix. In contrast, WC displayed significant dissolution and the formation of W-rich network structures, indicating a gradient-type interface.
The final focus of this research investigates “metallurgical defects”, focusing on solidification cracking in high-strength aluminum (HS-Al) alloys. Phase-field modeling based on the Ohno–Takaki framework was employed to capture AM-specific solidification behavior. The simulations showed that columnar grain morphologies increase cracking susceptibility, while the introduction of TiC nucleating particles refined grains, disrupted interdendritic liquid channels, and mitigated cracking. These results demonstrate the utility of phase-field modeling in guiding defect-control strategies and highlight nucleating particles as a promising approach to reduce solidification cracking in HS-Al alloys.
By addressing these interconnected challenges, this dissertation advances strategies to mitigate mechanical anisotropy, optimize interfacial properties, and minimize metallurgical defects in AM materials. These insights strengthen the reliability of high-performance AM components and support their wider adoption in critical industries.
Recommended Citation
Dixit, Som, "Additive Manufacturing of High-Performance Materials: Mechanical Anisotropy, Interfacial Properties, And Metallurgical Defects" (2025). All Dissertations. 4175.
https://open.clemson.edu/all_dissertations/4175
Author ORCID Identifier
https://orcid.org/0000-0002-0419-1428