Wire Arc-based Additive Manufacture (WAAM) is an open architecture high deposition rate process suitable for building large-scale aerospace components. However, the relatively large heat source and thick layer height leads to lower cooling and solidification rates than are normally found in smaller-scale powder bed AM processes, which can cause significantly greater microstructural heterogeneity and anisotropy.
In particular, titanium materials deposited by high deposition rate AM can have very coarse primary grain structures and significant texture. The overlap of the thermal field from sequential passes also leads to more severe heat affected zone banding. A fuller understanding of these issues will be presented and the potential for using both process and alloy modification to improve the deposited materials discussed, based on in-depth analysis of the material response. The research presented is supported by novel results involving automated microstructure quantification over large sample areas and in-situ experiments, and will include; the effect of thermal banding and texture on the micromechanical behaviour of titanium, the limitations of process parameters in reducing the primary beta grain size, and the benefits of combining AM with deformation to refine the grain structure, on. In addition, the potential for the application of high deposition rate AM to higher performance Ti alloys (e.g. 5553) and ‘tailored’ microstructures will be discussed.