Effect of lithium anti-ablation and grain refinement introduced by TiC nanoparticles in LPBF Al-Li alloy

Al-Li alloys are extensively utilized in the field of aerospace due to their low density and high specific strength. However, laser powder bed fusion (LPBF) processed Al-Li alloys still encounter challenges because of hot cracking and Li element ablation. In this study, a TiC nanoparticle modified Al-Mg-Li alloy is developed for LPBF process. Full dense printed TiC modified Al-Mg-Li alloy can be obtained. The presence of TiC nanoparticles in the melt pool effectively increased the viscosity of Al alloy liquid, leading to a reduction in the metal vapor-ization and liquid spatters, thus preventing the Li ablation during LBPF. The Li content was significantly increased from 0.87 wt.% in the Al-Mg-Li alloy to 1.34 % in the TiC modified Al-Mg-Li alloy. Moreover, the TiC nanoparticles played a key role in transition of columnar to equiaxed grain. The average grain size of TiC modified Al-Mg-Li alloy was refined to about 1.5 mu m, two orders of magnitude smaller than that in printed Al-Mg-Li alloy. A gradient transition reaction from TiC to Al3Ti was found on the TiC nanoparticles surface during LPBF. The in-situ formed Al3Ti phase on TiC nanoparticles significantly decreased the lattice mismatch with Al matrix, thereby resulting in an outstanding mechanical property of ultimate tensile strength of 343 MPa and elongation of 9.3 %. The effect of Li element anti-ablation induced by TiC nanoparticles provided a new pathway for additive manufacturing light-weight alloy.