Study on the mechanical properties of Al-Cu alloy fabricated by inter-layer hammering hybrid wire arc directed energy deposition: Experiments and crystal plasticity finite element method

Inter-layer deformation serves as an effective strategy to refine the micro-structure of wire arc-directed energy deposition (WA-DED), enabling the formation of periodic heterogeneous structures with alternating coarse grains (CG) and fine grains (FG) region. However, the mechanical behavior of such periodic micro-structures remains inadequately explored. This work provides a novel methodology for studying the deformation behavior of materials fabricated via IH hybrid WA-DED processes. The crystal plasticity finite element method (CPFEM) was first used in this study to investigate the evolution of mechanical properties of layered heterogeneous structures produced during the Inter-layer hammering (IH) WA-DED process under tensile simulation, establishing the relationship between microstructure and properties. The IH process yielded a Cube texture dominated micro-structure, with CG displaying a marginally higher Schmid factor (0.478) than FG (0.465). Notably, CG region exhibited elevated geometric compatibility factors (m′) at grain boundaries compared to FG region, promoting preferential dislocation slip activation and enhanced strain accommodation in CG region. CPFEM results demonstrated that slip systems in CG region were initially activated during the early plastic deformation stage. As deformation progressed, the distinct strain accommodation capacities between CG and FG region induced transverse cracks along the FG/CG interfaces to the tensile direction. Combined analysis of Schmid factors and m′ revealed that slip systems were predominantly activated perpendicular to the tensile direction, driving the nucleation and propagation of ductile cracks along this orientation. The interplay between single-slip system activation and dislocation motion emerged as the dominant deformation mechanism in the IH specimen, resulting in complex stress-strain distributions. These findings highlight the critical role of heterogeneous micro-structural features in governing deformation mechanisms and damage evolution in WA-DED processed alloys.