Influence of deposit and process parameters on microstructure and mechanical properties of Ti6Al4V obtained by DED-W (PAW)

Abstract

Direct energy deposition with a wire feedstock (DED-W) of Ti6Al4V is a promising solution to produce large structures with a better buy-to-fly ratio than conventional manufacturing techniques. This study investigates the potential of a plasma arc welding (PAW) as a heat source for DED-W. In order to understand the influence of process parameters on material health, microstructure and mechanical properties, three types of specimens: (i) single deposits; (ii) stacked-deposits walls and (iii) three-dimensional block are built. Two sets of parameters have been determined via deposit energy versus wire feed speed's process windows in order to obtain either slender or wide elements. The adoption of an increased deposit energy for the first several layers radically decreases the necking at the connection with the base plate. Prior β grain's width increases with the time spent above the β transus, which is dictated by the height of the build. On the other hand, α plate's thickness might be governed by the delay between layers which changes the cooling rate. Strain localisation under tensile loading appear either on banding or in the vicinity of αgb layer. Mechanical properties anisotropy related to the columnar shape of prior β grains is more noticeable under Charpy notched impact tests than tensile tests.