Jack Beuth (Committee Member), Srikanth Bontha (Committee Member), Nathan Klingbeil (Advisor)
Master of Science in Engineering (MSEgr)
Laser and electron beam-based additive manufacturing of Ti-6Al-4V are under consideration for application to aerospace components. A critical concern for these processes is the ability to obtain a consistent and desirable microstructure and corresponding mechanical properties of the deposit. Based on the Rosenthal solution for a moving point-heat source, recent work has developed simulation-based process maps for the thermal conditions controlling microstructure (grain size and morphology) in beam-based deposition of semi-infinite geometries, where a steady-state melt pool exists away from free-edges. In the current study, the Rosenthal solution is modified to include the effects of free-edges. This is accomplished by the superposition of two point-heat sources approaching one another, with the line of symmetry representing the free-edge. The result is an exact solution for the case of temperature-independent properties. Dimensionless results for melt pool geometry, solidification cooling rate and thermal gradient are determined with MATLAB, and plotted as a function of distance from the free-edge. Finite element analysis is used to verify results for 2-D and 3-D geometries in both small-scale and large-scale (higher power) processes. Results are further plotted on solidification maps to predict trends in microstructure for Ti-6Al-4V. Results suggest that melt pool geometry is more sensitive to free-edges than solidification microstructure, particularly for small-scale processes. This is an important result for process developers.
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
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