Researchers from Harbin Institute of Technology and De Montfort University published a study in Advanced Materials Joining: During cold metal transfer (CMT) wire-arc additive manufacturing (WAAM) of nickel-aluminum bronze, an ethanol solution of 50 nm titanium powder was ultrasonically dispersed and brush-coated between each weld bead layer (concentrations of only 0.03/0.05/0.1 wt%). After ethanol evaporation, the next arc remelted the titanium nanoparticles directly into the molten pool, achieving in-situ microalloying without additional heat treatment steps. The effect of titanium content on grain structure is non-monotonic: at 0.03 wt%, grains coarsened to 75.2 μm (unmodified 39.1 μm, about 65% of titanium particles did not act as nucleation sites); at 0.05 and 0.1 wt%, heterogeneous nucleation and Zener pinning refined grains to 17.3 μm and 21.6 μm. The alloy maintains an α matrix, β′ martensite, and κ phases, with no new titanium phases formed. Strengthening mechanisms are grain refinement and solid solution strengthening. Performance: Hardness increased by 6–8% (maximum about 195.6 HV, unmodified 181.2 HV); the 0.1 wt% titanium sample achieved longitudinal tensile strength of 718.2 MPa (unmodified 664.2 MPa), yield strength of 372.5 MPa, and maintained the corrosion resistance advantage of nickel-aluminum bronze, verified by 7/14/21-day immersion and electrochemical polarization tests in 3.5 wt% NaCl solution. Value for powder buyers: ① The in-situ brush-coating method opens a 'nanotitanium powder + wire' composite process route, creating new application scenarios for 50 nm-grade titanium powder in copper alloy modification; ② WAAM adoption for marine propellers, valves, underwater pipelines, and other components is constrained by process maturity, and this study provides a heat-treatment-free modification solution; ③ It is recommended to focus on the dispersibility and stable supply capability of nanoscale titanium powder, as demand for such microalloying additives is expected to expand with WAAM mass production.