The adjustment of the microstructure through parameter variation in laser powder bed fusion (PBF-LB/M) is restricted by the process stability and quality limitations. These limitations can be overcome by combining the PBF-LB/M using a cw laser source with ultrashort pulsed laser ablation. This enables to add heat-dissipation structures during the printing process to change the local temperature field, which leads to a change in the solidification conditions and thus the resulting microstructure. Such additional heat dissipation structures can be ablated after solidification using ultrashort laser pulses, thus retaining the original component geometry. In addition, the ultrafast laser can be used to ablate narrow slits that act as a heat barrier. Both strategies can purposefully adjust the local temperature field, including the solidification conditions for the individual layers in PBF-LB/M.

The potential of microstructure adjustment, in combined additive and subtractive (AddSub) laser material processing was numerically and experimentally analyzed for components of the aluminum alloy AlSi10Mg. Parts with different geometries of heat-dissipation structures and different ablation strategies were manufactured. The microstructure was analyzed using metallographic analysis and the hardness was measured. The results show significant changes in the microstructure depending on the ablation strategy and the geometry of the heat dissipation structures.