A High-Strength TiB₂-Modified Al–Si–Mg–Zr Alloy Fabricated by Laser Powder-Bed Fusion

To increase the strength of the laser powder-bed fusion (LPBF) Al–Si-based aluminum alloy, TiB₂ ceramic particles were selected to be mixed with high-Mg content Al–Si–Mg–Zr powder, and then a novel TiB₂/Al–Si–Mg–Zr composite was fabricated using LPBF. The results indicated that a dense sample with a maximum relative density of 99.85% could be obtained by adjusting the LPBF process parameters. Incorporating TiB₂ nanoparticles enhanced the powder's laser absorption rate, thereby raising the alloy's intrinsic heat treatment temperature and consequently facilitating the precipitation of Si and βʺ nanoparticles in the α-Al cells. Moreover, the rapid cooling process during LPBF resulted in numerous alloying elements with low-stacking fault energy dissolving in the α-Al matrix, thus promoting the formation of the 9R phase. After a 48 h direct aging treatment at 150 °C, the strength of the alloy slightly increased due to the increase of nanoprecipitates. Both yield strength and ultimate tensile strength of the LPBF TiB₂/Al–Si–Mg–Zr alloy were significantly higher than that of other LPBF TiB₂-modified aluminum alloys with external addition.