Nickel–Aluminum–Bronze (NAB) has gained significant attention in marine applications due to its excellent corrosion resistance and has shown growing potential for laser powder bed fusion (L-PBF) additive manufacturing. However, research on the fabrication of NAB alloys using L-PBF remains relatively limited. In this study, fully dense NAB samples were successfully fabricated through L-PBF process parameter optimization. The microstructural evolution and mechanical properties of both as-built and annealed L-PBF samples were systematically investigated and compared with those of traditionally cast NAB. The results reveal that the as-built L-PBF specimens primarily consist of columnar β′ grains, with the α phase distributed along the grain boundaries and a small amount of κ phase precipitated within the β′ matrix, distinctly different from the cast microstructure characterized by a columnar α-phase matrix with precipitated β′ and κ phases. After annealing at 675 °C for 6 h, the β′ phase in both methods decomposed into α + κ phases, and the original columnar structure in the L-PBF specimens transformed into a dendritic morphology. Compared to the cast samples, the L-PBF-produced NAB alloy exhibited significantly enhanced yield strength, tensile strength, and microhardness, attributable to rapid solidification during the L-PBF process. Following annealing, the yield strength and elongation increased by 12.8% and 184.4%, respectively, compared to the as-built condition, resulting from the decomposition of the martensitic phase into α + κ phases and further grain refinement.

Cyclic superelasticity in laser powder bed fusion (LPBF)-fabricated NiTi alloys is strongly influenced by the scale of structural regulation. While conventional post-processing strategies are typically interpreted from a microstructural perspective, the distinct roles of bulk and surface regulation in governing cyclic functional response remain unclear. In this study, heat treatment and laser shock peening (LSP) are employed as representative bulk and surface regulation routes, respectively, to systematically investigate their effects on phase transformation and cyclic superelasticity. The results reveal that heat treatment and LSP operate through fundamentally different regulation modes. Heat treatment acts as a bulk regulation route, reconstructing the overall microstructure, promoting precipitation (NiTi₂ and Ni₄Ti₃), and modifying transformation pathways, which enhances recovery ratio but reduces recoverable strain. In contrast, LSP acts as a surface/subsurface regulation route, inducing gradient grain refinement and near-surface hardening while maintaining a B2-dominated matrix. As a result, the LSP-treated sample exhibits superior cyclic stability, with a stable recoverable strain of 9.93% and a superelastic strain of 5.10% after 10 cycles. These findings demonstrate that cyclic superelasticity is governed not only by phase constitution but also critically by the scale of structural regulation. This work provides a practical framework for selecting post-processing strategies to optimize functional performance in LPBF NiTi alloys.