Nathan Klingbeil (Advisor), Raghavan Srinivasan (Committee Member), Jaimie Tiley (Committee Member)
Master of Science in Engineering (MSEgr)
The success of laser and electron beam-based fabrication processes for additive manufacture and repair applications requires the ability to control melt pool geometry while maintaining a consistent and desirable microstructure. Previous work has employed a process map approach to link melt pool geometry to solidification microstructure (grain-size and morphology) in beam-based fabrication of Ti-6Al-4V. The current work extends the approach to investigate the effects of process variables on solid-state phase transformations below the solidification temperature through Finite Element Modeling, the 3-D Rosenthal Solution, and experimentation. Process maps for solid-state microstructure could be used to help maintain consistent and reliable mechanical properties during deposition of complex features. The characterization of seventeen Ti-6Al-4V samples was completed through Electron Backscatter Diffraction, X-ray Diffraction, Vickers Hardness tests. The solid-state transformation of Ti-6Al-4V was investigated to find trends in beta grain size, alpha lath thickness, and types of alpha microstructures. Thermal conditions and melt pool areas were verified with Finite Element Analysis and the fitted Rosenthal solution. Results suggest the solid-state alpha morphology is uniform because of constant melt pool area, constant grain area, and constant Vickers Hardness tests.
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
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