Microstructure and mechanical properties of a structurally refined Al–Mg–Si alloy for wire-arc additive manufacturing

Wide-spread utilization of wire-arc additive manufacturing (WAAM) technologies require the development of high-performance aluminum alloys with a robust processing window. Suitable alloys have to be modified to reduce their susceptibility for hot cracking - a common means is grain refinement via inoculation. Here, an advanced Al–Mg–Si alloy with a TiB2 containing structural refiner is processed using WAAM. As a result, no macroscopic cracks are observed in the deposit. The microstructure consists of fine (<30 μm) and equiaxed grains that do not show any crystallographic texture. Both characteristics are considered to result from preferential heterogeneous nucleation yielding a reduced tendency for epitaxial nucleation. No coarsening of the heterogeneous nucleants is observed when comparing wire and WAAM deposit microstructures. After a two-step heat treatment, where negligible grain coarsening is observed during the solution heat treatment, the yield strength reaches ∼ 265 MPa irrespectively of the tensile direction. Gained results provide the basis for the application of an advanced Al–Mg–Si alloy using the WAAM technology.