Title: Functionally-graded materials and complex alloy systems through wire-arc additive manufacturing

Abstract

Wire-arc additive manufacturing (WAAM) is receiving increasing attention due to advantages in terms of component costs, deposition rate and buy-to-fly ratio of structures of medium-to-large complexity. The use of multiple alloy wires during WAAM is of particular interest as the chemical composition of the deposit can be adjusted according to the structure’s requirements without the limitation of commercially available welding wires. Additionally, the local chemical compositions may be adjusted yielding novel physical and mechanical properties of such functionally graded materials (FGM). The present work explores options for the fabrication of structures using multiple feedstock wires to a deposit a FGM and b deposit alloy compositions of commercially unavailable materials. For the deposition gas tungsten arc welding (GTAW) is used. Resultant materials are characterized regarding chemical composition, microstructure and mechanical properties. Utilizing tailored processing conditions the fabrication of a chemical gradient was verified by optical emission spectroscopy along the specimen height with the results for Si. The major findings of the presented research can be concluded as follows: WAAM using two feedstock wires is not only feasible but allows for flexibility in the processing routine; The adjustment of new alloy compositions by mixing the respective feedstock wires in situ during processing is possible with sufficient intermixing; Microstructures and resultant properties can thereby be adjusted locally; The outcomes of this work expand the applicability of WAAM as additional design freedom is gained for the fabrication of structures and components.