MTE PhD Dissertation Defense, Yuwei Zhai


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Yuwei Zhai
Wednesday, April 18, 2018
2:00 pm to 4:00 pm
Floor/Room #: 
HL 102


Microstructure Evolution, Static and Dynamic Properties, and Fatigue Damage Mechanisms in Ti-6Al-4V and Inconel 718 Fabricated by Laser Engineered Net Shaping (LENS®)

As the industry pushes for the implementation of Additive Manufacturing (AM) technology, a focus of efforts is now on the qualification and certification of AM processed materials. For critical applications in the field of aerospace, defense, medical etc., the fatigue and fracture resistance of materials are among the most important design criterions. Therefore, qualification of AM processed materials for such critical applications requires extensive examination of their fatigue and fatigue crack growth properties, and understanding of the fatigue failure mechanisms. This study investigates two important aerospace alloys, Ti-6Al-4V and Inconel 718, fabricated by the Laser Engineered Net Shaping (LENS®) technique. For each material, systematic evaluations of the tensile and fatigue crack growth properties are performed in both as-built and heat treated conditions. Post testing analysis reveals the contribution to damage from certain microstructural features, defining favorable as opposed to detrimental microstructural conditions. These observances provide important guidelines for further modification of processing and heat treating procedures. This study establishes the process – structure – property relationships for each investigated alloy, and demonstrates the application of such knowledge in design with AM.