On the novel precipitation sequence of the TiN modified Al-Mn-Sc alloy processed by laser powder bed fusion

The influence of TiN addition on the new precipitation sequence and hardening effects of TiN modified Al-Mn-Sc alloy processed by LPBF was systematically studied in this work. The diffusion behavior of TiN particles results in obvious difference in the main alloying elements concentrations, altering the lattice constants of both primary and secondary L1 2 -Al 3 (Ti,Sc,Zr) precipitates in the alloy matrix composite. After being subjected to peak-aging treatment, a novel precipitation sequence was observed in the sample containing 1.5 wt% TiN via generating a higher volume fraction of coherent L1 2 -Al 3 Sc and semi-coherent rod-like Al 6 (Mn,Fe) precursors, corresponding to an alleviated internal strain as well. This new phenomenon has been demonstrated as a novel hardening mechanisms contributing to both microstructure refinement and mechanical property enhancement. As the results, the sample containing 1.5 wt% TiN exhibits an ultra-high yield strength of 651 ± 7 MPa and a compensate fracture elongation rate of 3.9 ± 0.3 %.