Evading ductility deterioration in aluminum matrix composites via intragranulation of nano-reinforcement by reactive selective laser melting

Strengthening of metals via compositing is accompanied with ductility deterioration. To evade this deficiency, we proposed intragranulation of nano-reinforcement in aluminum matrix composites (AMCs) via reactive Selective Laser Melting (SLM). SiC nanoparticles (SiC_np) and pure Al were selected to facilitate the reaction during SLM. Different from the SiC_np residing at primary powder boundaries in spark plasma sintered composites, during SLM, the SiC_np completely reacted with Al and formed in-situ intragranular nanophases, viz. Si nanoparticles and Al₄C₃ nanorods. The intragranular Si and Al₄C₃ resulted in a high strengthening efficiency (∼110%) at no expense of ductility. With 0.6 vol% of SiC_np, 53% of tensile strength increase and 19% of ductility increase were achieved simultaneously. Post-tensile TEM observations revealed that those intragranular nanophases pinned and accumulated dislocations in the grain interior. This study may open up a new direction in developing high-performance AMCs.