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 TiB2 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 TiB2 particles and the segregation of excess Ti at their surface promotes the formation of Al₃Ti. After solution treatment and aging, differences in Al₃Ti precipitation behavior 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 TiB2 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).