Laser additive manufacturing of novel Al-matrix composites reinforced with high-volume multiscale in-situ Al4C3

In this work, novel Al-matrix composites (AMCs) reinforced with a high-volume fraction of multiscale in-situ Al 4 C 3 were successfully fabricated via laser powder bed fusion (L-PBF) using Al-12Si/carbon fibers (CFs) mixed powders. Owing to the steep thermal gradients and rapid solidification inherent to the L-PBF process, two distinct types of in-situ Al 4 C 3 reinforcements were formed: reaction-formed high-aspect-ratio (HAR, ∼60) Al 4 C 3 rods and precipitation-formed medium-aspect-ratio (MAR, ∼15) Al 4 C 3 nanorods. As a result, the in-situ composite prepared from Al-12Si/10%CFs powder mixture achieved a tensile strength of 66.8 MPa at 673 K, approximately three times higher than that of the unreinforced alloy (22.1 MPa). This improvement is primarily attributed to load transfer strengthening provided by the HAR-Al 4 C 3 rods, and Orowan strengthening induced by the MAR-Al 4 C 3 nanorods. These findings provide new insights into the design and laser additive manufacturing of next-generation in-situ AMCs.