Suppressing interlayer liquation cracking in WAAM AlCu5MnCdV alloy by pre-laser melting of TiC particles

Interlayer liquation cracking in wire-arc additive manufacturing(WAAM) of high-strength cast AlCu5MnCdV alloys remains a critical challenge. To address this, a novel pre-laser melting (PLM) of TiC particles strategy was developed, employing an oscillating laser to pre-melt TiC particles ahead of arc. Distinct from previous qualitative understanding of TiC's heterogeneous nucleation, a cellular automaton model incorporating precipitate evolution was developed to quantitatively reveal the microstructure evolution within the crack-sensitive remelting zone. The simulation revealed that PLM TiC notably accelerated solidification, especially in the final stage of this critical region, where earlier nucleation within a ∼40 μm region, advanced solid-liquid interface by ∼402 μm and shortened solidification period by ∼0.23 s. This transformed the coarse columnar grains into a fully refined equiaxed structure, suppressing the continuous Al₂Cu networks, grain boundaries (GBs) holes and liquid films during final solidification stage of remelting area. Thus, higher stability was obtained due to the refined precipitates with alleviated Cu segregation (51.5 wt% to 38.5 wt%), which prevented liquation cracking during T5 heat treatment. The refined semi-coherent Al₂Cu precipitates and ∼3.8% lattice distortion in Al matrix were obtained in PLM TiC-T5 sample, contributing to the improvement in tensile strength from 358 MPa to 485 MPa in travel direction. In the building direction, the tensile strength was increased from 155 MPa to 436 MPa, with 140.8 MPa from crack elimination and the rest from microstructural optimization. This work extended the applicability of ceramic particle regulation in WAAM via laser assistance, and provided a viable pathway for fabricating crack-free, high-strength aluminum alloys.