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 beta" nanoparticles in the alpha-Al cells. Moreover, the rapid cooling process during LPBF resulted in numerous alloying elements with low-stacking fault energy dissolving in the alpha-Al matrix, thus promoting the formation of the 9R phase. After a 48 h direct aging treatment at 150 degrees 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.