Understanding and clarifying the formation and evolution mechanism of the microstructure in wire + arc additive manufacturing (WAAM) Al-Cu alloy is primary and essential for achieving the higher and more isotropic mechanical properties. In this study, the evolution of grain structure, precipitated phases and corresponding mechanical properties of the as-deposited WAAM processed 2219 Al-Cu alloy are investigated. The microstructure exhibits the heterogeneous band characteristics between the fine equiaxed α-Al grains in inter-layer zone (ITZ) and the columnar α-Al grains in inner-layer zone (INZ). Based on the re-melting experiment and the time-dependent nucleation theory, the occurrence of equiaxed grains is attributed to the heterogeneous nucleation of α-Al caused by the prior precipitation of Al₃Zr particles at the molten pool boundaries. The relationship between the solidification conditions and the number of the prior Al₃Zr nucleation sites is established. A large amount of spherical θ″-Al₂Cu phases precipitate in Cu-rich regions around the α-Al+θ-Al₂Cu eutectics and they agglomerate and transform to flaky-like θ′ phases under the in-situ thermal effect during WAAM deposition. The hardness of the ITZ (81 ± 2.7HV) is approximately 12% higher than that of the INZ (74 ± 3.6HV) which is mainly due to the finer grains and the more dispersive precipitates in ITZ.

了解和阐明焊丝 + 电弧增材制造 (WAAM) Al-Cu 合金微观结构的形成和演化机制，对于实现更高和更各向同性的机械性能至关重要。在这项研究中，研究了沉积态 WAAM 处理的 2219 Al-Cu 合金的晶粒结构、沉淀相和相应的机械性能的演变。显微组织表现出层间区（ITZ）的细小等轴α-Al晶粒和内层区（INZ）的柱状α-Al晶粒之间的异质带特征。根据重熔实验和时变形核理论，等轴晶的出现是由于Al ₃预先析出导致α-Al的异相形核。熔池边界处的 Zr 颗粒。建立了凝固条件与先前Al ₃ Zr 形核位点数量之间的关系。α-Al+θ-Al ₂ Cu 共晶周围富铜区域析出大量球形 θ ″ -Al ₂ Cu 相，在原位热效应下，它们团聚并转变为片状 θ ′相。 WAAM 沉积。ITZ的硬度（81±2.7HV）比INZ的硬度（74±3.6HV）高约12%，这主要是由于ITZ的晶粒更细，析出物更分散。