| Abstract Scope |
Refractory metal alloys have a variety of benefits that drive their application in harsh environments. This includes a high melting point and wear resistance. Tantalum is a refractory metal utilized for its relatively good ductility, processability, weldability and biocompatibility compared to other refractory metals. Alloying of Tantalum with other refractory materials is utilized to improve properties including strength, hardness, and corrosion resistance. With this improvement in behavior, a decrease in weldability and subsequently additive manufacturability is seen. A high ductile to brittle transition temperature (DBTT) is the leading cause for cracking in AM of refractory materials. Laser direct energy deposition (DED-L) is an additive manufacturing technique popular in alloy design. DED-L can utilize multiple powder hoppers. This allows for in-situ elemental mixing and testing of various compositions within a single build. For this work Calphad modeling was used to determine equilibrium and non-equilibrium behavior within the material. A surrogate model was selected to determine the material ductility based on stacking fault and surface energies. This approach has been shown to be successful in predicting room temperature ductility. Work has been done to correlate this model to DBTT in refractory materials. Test coupons were printed with a five hopper (DED-L) printer to control composition. Each composition was printed under varying print conditions. Composition and microstructure were analyzed through SEM, EBSD, EDS, and XRD for calphad model validation. Crack density was calculated for each composition across the range of print parameters to understand relative printability and compared to surrogate ductility modeling. |