Microstructure evolution and strengthening mechanisms of a high-performance TiN-reinforced Al-Mn-Mg-Sc-Zr alloy processed by laser powder bed fusion

In this work, a high-strength crack-free TiN/Al-Mn-Mg-Sc-Zr composite was fabricated by laser powder bed fusion (L-PBF). A large amount of uniformly distributed L12-Al3(Ti, Sc, Zr) nanoparticles were formed during the L-PBF process due to the partial melting and decomposition of TiN nanoparticles under a high temperature. These L12-Al3(Ti, Sc, Zr) nanoparticles exhibited a highly coherent lattice relationship with the Al matrix. All the prepared TiN/Al-Mn-Mg-Sc-Zr composite samples exhibit ultrafine grain microstructure. In addition, the as-built composite containing 1.5 wt.% TiN shows an excellent tensile property with a yield strength of over 580 MPa and an elongation of over 8%, which were much higher than those of wrought 7xxx alloys. The effects of various strengthening mechanisms were quantitatively estimated and the high strength of the alloy was mainly attributed to the refined microstructure, solid solution strengthening, and precipitation strengthening contributed by L12-Al3(Ti, Sc, Zr) nanoparticles.