Simulation and Characterization of Electron Beam Additive Manufacturing Ti-6Al-4V

Electron beam additive manufacturing processes based on the addition of liquid metal to a substrate offer an attractive alternative to the machining of large parts. However, this process presents challenges in control of thermally induced issues. 3D FEM simulation can be performed to study the thermal-mechanical behavior during electron beam additive manufacturing using the commercial software Abaqus®. A comprehensive fully-coupled thermal stress model is developed for predicting the temperature, stress and strain history and the type of microstructure. Marangoni flow as well as latent heat are considered to obtain a more accurate temperature gradient. This model provides a quantitative relationship between process parameters and desired microstructures and properties, which could reduce the cumbersome and time-consuming experimental route for tailoring material behavior. Results of simulation were validated experimentally to provide confidence in using simulations for process optimization. Both single layer, single pass and single layer, three pass plates are investigated.  EDS results indicate no significant material evaporated during additive manufacturing which matches with the temperature field calculated from the model. The estimated size of the molten pool agrees with the result of metallographic examination. Microstructures could be reasonably determined according to the simulation thermal profile. The distortion maps of the plates are plotted using a coordinate measurement machine and are compared with the simulation results. The reliability and the accuracy of the model are verified.