Measurement and Simulation of Titanium Alloy Deposit Temperature in Electron Beam Additive Manufacturing

Using the electron beam welding process for direct manufacturing (EBDM) offers the potential to rapidly produce complex, near-net shaped metal alloy products in dramatically less working time, at significantly lower cost compared to traditional manufacturing methods such as casting/forging and with much less machining / much lower material waste in final form.  In addition, there are potential added quality and versatility benefits unique to additive processes with EBDM. lncremental part quality may be cumulatively verified for each item produced as the product builds; this is an opportunity to query the "total process quality timeline" rather than off-part surrogate testing and/or lot sampling at process end which do not verify quality as comprehensively. There is also an opportunity with EBDM to tailor and verify differing application-specific properties in different areas of the product. Much of the present literature on EBDM has focused on boosting metal deposition rate to increase productivity.  This work begins to focus on an important next step for the EBDM process: controlling the process to yield parts with the desired microstructure/mechanical properties.  Mechanical properties are a result of microstructure which in turn is a function of process parameters.  In this work, a transient finite element model of the EBDM process is developed for Ti-6Al-4V.  The model is tuned using experimental data gathered from a variety of in-process sensors.  The model is used to predict solidification and cooling rates for simple built-up structures at various preheat temperatures.  The model can simulate thermal histories over a range of welding parameters which are cost prohibitive to cover experimentally.  The results show welding process parameters can be directly correlated to microstructure features.