Improving ductility via grain structure control in Sc/Zr modified Al-Cu-Li alloys by pulsed-laser powder bed fusion

Sc/Zr modification significantly enhances the printability of high-strength Al-Cu-Li alloys, but poor ductility continues to limit the application of additive manufactured aluminum alloys as advanced component. Here, we proposed a point-by-point deposition strategy based on pulsed-laser powder bed fusion (PLPBF) to precisely control grain structures in Sc/Zr modified Al-Cu-Li alloys. This method successfully breaks the characteristic of melt pool under traditional continuous laser mode, making each ‘point’ melt pool has an independent solidification process. It facilitates the remelting of columnar grains within the melt pools while preserving the equiaxed grains at the edges. Leveraging the spatial distribution features, columnar grains are completely eliminated, resulting in a fully equiaxed grain structure in the printed sample. Meanwhile, the average grain size is reduced by 40%, accompanied by a slight increase in the volume fraction of Al3(Li,Sc,Zr) precipitates. The samples fabricated via pulsed laser exhibit a remarkable 211% improvement in elongation compared to those fabricated by continuous laser, with only a minor 7.6% decrease in tensile strength due to the shift from heterogeneous deformation induced (HDI) strengthening to grain refinement strengthening. This strategy enables tunable microstructural design in various alloy systems, offering enhanced flexibility to balance strength and ductility for advanced engineering applications.