Ultra-high strength and superior corrosion resistance of additively manufactured 7075 aluminum alloys enabled by in-situ formed nanoceramic particles and their underlying mechanisms: W2C and TiB2

Strength and corrosion resistance of alloys typically conflict with one another. Herein, WC and B+TiH 2 were coated onto 7075 aluminum alloy powders via liquid-phase and dry mechanical coating, respectively, for the fabrication of SLM 7075 alloys reinforced by in-situ generated W 2 C and TiB 2 nanoparticles, seeking to realize concurrent improvements in mechanical strength and corrosion performance. The results show that incoherent disk-shaped W 2 C particles increase compressive strength by over 20% but deteriorate ductility and corrosion resistance. By contrast, semi-coherent blocky TiB 2 particles, with an orientation relationship of and a lattice mismatch of 9.5%, raise the compressive strength of the SLM 7075 alloy from 459 MPa to 983 MPa, increase the compressive strain from 17.4±2.1% to 45.8±1.9%, and simultaneously reduce corrosion susceptibility. W 2 C only delivers limited grain refinement (15.4%) and slight texture strengthening, while TiB 2 achieves ∼80% grain refinement and homogenises geometrically necessary dislocations, enabling strength-ductility synergy. Quasi-in-situ STEM-HAADF characterizations confirm corrosion originates from micro-galvanic coupling between Mg-Zn-Cu-rich grain boundary precipitates and the Al matrix. Though electrochemically inert, W 2 C and TiB 2 induce distinct corrosion behaviors by tailoring grain boundary structures. Grain-boundary-segregated W 2 C forms extra cathodic sites, widens grain boundaries by ∼27% and aggravates coalesced pitting. By contrast, intragranular TiB 2 refines grains, narrows grain boundaries by ∼83%, interrupts dissolution pathways, suppresses hydrogen evolution and retards localized corrosion. This work reveals their distinct modulation mechanisms, providing guidance for high-performance additively manufactured aluminum composites.