Additive manufacturing technologies gain increasingly interest in industry and academia in a broad spectrum of different fields like the transportation, energy, tooling or medical sector for fabrication of custom solutions or repair of damaged components. Especially wire laser direct energy deposition (wire L-DED) attracted attention as a promising candidate for large-scale structural applications due to its standardised feedstock materials and its easy-to-realise safety requirements.

However, the inherent thermal boundary conditions of the L-DED process can have adverse effects on the formation of the microstructure. Typically, a strong directional heat flux against the built direction through the substrate material is present during fabrication. Consequently, the growth of coarse columnar grains with a strong fibre texture (<100> for cubic metals) along the built direction is observed yielding unfavourable anisotropic mechanical properties in as-built components. Overcoming these thermal limitations and disrupting the highly directional solidification mechanisms might be a tool to push the possibilities and performance of wire L-DED components even further.

Traditional methods to induce grain refinement and a more isotropic texture either imply a change of alloy composition by nucleant particles or require complex process setups for thermomechanical machining of intricate L-DED parts. This lecture presents a promising, unique approach to introduce grain refinement by ultrasonic excitation of the melt pool during wire L-DED. An ultrasound system was developed and integrated in a laser wire deposition machine. A suitable process has been established and, by means of metallurgical analysis, it is demonstrated that a controlled introduction of ultrasound into the melt pool disrupts the highly directional solidification mode and promotes the formation of a randomized texture as well as refined grain structure (dm = 284,5 µm without ultrasound, dm = 130,4 µm with ultrasound).