Achieving ultra-high strength of laser powder bed fusion TiN nanoparticles reinforced AlMnMgScZr composite via a high volume density of L12-nanoprecipitates

In this paper, a novel design strategy for l-PBFed AlMnMgScZr/TiN composites with ultrahigh strength was proposed. TiN particles can not only function as ceramic reinforcement, but also decompose and reprecipitate to form a large density of L1₂-precipitates at a high melting temperature during l-PBF. Meanwhile, the primary L1₂-Al₃X (X=Ti/Sc/Zr) phase promotes the columnar-to-equiaxed grain transition effect, creating a fine bi-modal grain structure in the as-built sample. A high volume fraction of L1₂ nanoparticles are additionally precipitated from Al matrix during post heat treatment. In this regard, effective grain refinement and precipitation hardening mechanism contribute to an excellent tensile performance with a combination of an ultimate tensile strength of 681±4 MPa, a yield strength of 677±4 MPa, and an elongation rate of 5.4 ± 1.2%. The yield strength of 677 MPa is particularly the highest among all previously reported l-PBFed Al matrix composites and Al alloys.