Boron-functionalized AlTiMgSi powders for in-situ precipitation of TiB2 grain refiners during laser powder bed fusion

Producing Al powder feedstock containing high levels of Ti and B through gas atomization remains technologically challenging. In this study, a different route is proposed based on the functionalization of powder surfaces rather than pre-alloying. A Ti-bearing Al-Mg powder was modified by decorating its surface with 0.5 wt.% of boron nanoparticles via a fluidized-bed process. This approach enabled powder surface decoration with B, leading to in-situ TiB 2 formation during Powder Bed Fusion - Laser Beam (PBF-LB/M), without the need for ex-situ ceramic additions. The approach, demonstrated here on an AlTiMgSi alloy, can be easily extended to other systems to design in-situ reinforced feedstocks for additive manufacturing. The results showed that the AlTiMgSi alloy is characterized by a partial suppression of epitaxial growth in PBF-LB/M due to the presence of Al₃Ti. In contrast, when B was added to the powder surface, the refinement effect was significantly enhanced , due to the combined effect of formation of TiB 2 particles and the segregation of excess Ti at their surface promotes the formation of Al₃Ti. After solution treatment and aging, differences in Al₃Ti precipitation behaviour were observed in the two investigated systems: the B-free alloy showed a dense distribution of acicular precipitates, whereas the functionalized alloy exhibited coarser and fewer Al₃Ti particles due to Ti consumption during TiB 2 formation. The AlTiMgSi(B) alloy exhibited higher ultimate tensile strength (305.7 ± 0.2 MPa) and yield strength (273.9 ± 8.1 MPa) compared to the B-free alloy (264.6 ± 5.9 MPa and 214.1 ± 0.2 MPa, respectively). • Novel powder AlTiMg decorated with B nanoparticles was produced • B enables in-situ TiB₂ formation during PBF-LB/M processing • TiB₂ and Al₃Ti jointly promote equiaxed grain refinement • B addition alters alloy precipitation behavior after T6 heat treatment