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 L12Al3X (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.