Ti addition-induced simultaneous enhancement of powder properties, melting behavior, and tensile response of pure Al for laser powder bed fusion

A lack of fusion and a high cracking tendency are two major bottlenecks in the fabrication of Al alloys via laser powder bed fusion (L-PBF). In this work, we demonstrate the fabrication of defect-free Al parts with enhanced mechanical performance using an in-situ Ti alloying approach. Pure Al and Ti powders with arbitrary composition ratios were uniformly mixed using a newly developed wet mixing method. As confirmed by powder property measurements, in-situ melting behavior evaluations, and simulations using a discrete element method and computational fluid dynamics (DEM-CFD) model, the addition of Ti effectively enhanced the powder flowability and laser absorptivity while reducing the surface tension of the Al melt. These improvements facilitated the formation of continuous and wider laser beads, ultimately leading to the densification of Al-Ti alloys. This result highlights the effectiveness of powder-centric design strategies in enabling the fabrication of advanced metallic components. As a result, the Al-10Ti alloy exhibited an excellent balance between a tensile strength of 124.8 MPa and ductility of 4.6% at 573 K, along with superior tensile strength retention compared to traditional Al alloys. The enhanced performance is primarily attributable to the presence of metastable L1 2 -Al 3 Ti phases, which features more slip systems and a greater capacity for plastic deformation, as well as the low diffusion coefficient of Ti in the Al matrix at elevated temperatures. Owing to the rapid cooling characteristic of L-PBF process, the high-symmetry L1 2 -Al 3 Ti structure was successfully formed in pure Al without the addition of stabilizing ternary elements. Overall, this study underscores the significant potential of combining the L-PBF process with powder design to fabricate high-performance Al alloys.