The synergistic influences of nano-TiC and Sc/Zr on the microstructural evolution and mechanical properties of additively manufactured Al-Mn-Mg-Sc-Zr alloys

Sc and Zr have been demonstrated to effectively enhance the printability and mechanical properties of aluminum alloys; however, the high cost of Sc limits their engineering applications. In this work, nano-TiC particles were introduced via a pre-alloying method, either as a partial substitute for Sc/Zr or as a direct addition, to investigate their synergistic contribution with Sc/Zr on the microstructure and mechanical properties of laser powder bed fusion (LPBF)-processed Al-Mn-Mg-Sc-Zr alloys. The results show that nano-TiC acts as a potent nucleation site for Al₃(Sc,Zr), refining coarse columnar grains and promoting grain refinement. Meanwhile, the incorporation of nano-TiC effectively modifies the precipitation sequence, promoting the formation of icosahedral quasicrystalline (i-QC) and Al₃₀Mg₂₃ phases. Following heat treatment, the precipitation of Al₆Mn, L12-Al₃(Sc,Zr), and Al₃₀Mg₂₃ phases provides pronounced precipitation strengthening, thereby improving the mechanical properties. The alloy in which Sc/Zr was partially substituted by nano-TiC demonstrated comparable performance to existing Al-Mn alloys, while effectively reducing the reliance on costly Sc and Zr elements. In contrast, the alloy with direct incorporation of nano-TiC exhibited superior strength, achieving a yield strength of 550 ± 9 MPa and an elongation of 7.1 ± 0.5% after heat treatment, along with isotropic mechanical behavior. This work demonstrates that the synergistic influence of nano-TiC and Sc/Zr can achieve a favorable strength-ductility balance while reducing material cost, providing new insights into the design of high-performance LPBF-processed aluminum alloys.