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 mu m) 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 similar to 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.

Automated summary

The study explores the processing performance of an advanced Al-Mg-Si alloy with a TiB2-containing structural refiner in WAAM technology, resulting in fine equiaxed grains without crystallographic texture, and showing good yield strength after heat treatment.