The influence mechanism of periodic heterogeneous distribution of microstructure on fracture behavior in the 2319 aluminum alloy of wire-arc directed energy deposition

The microstructure of aluminum alloy components fabricated by wire-arc directed energy deposition (wire-arc DED) has typical periodic heterogeneous distribution characteristics, which will directly affect the fracture behavior of the components. Therefore, in this study, 2319 aluminum alloy components were additively manufactured by Cold Metal Transfer wire-arc DED (CMT wire-arc DED) system. Viewing the cross sections of fracture morphology from horizontal and vertical directions, the influence mechanism of periodic heterogeneous distribution of microstructure on fracture behavior of aluminum alloy components was analyzed. The results show that the mechanical properties of the additive components have obvious anisotropy. The tensile strength and elongation of the transverse tensile specimens are better than those of the longitudinal tensile specimens, and the former have better mechanical properties. With the metallographic structure and electron back scatter diffraction (EBSD) test results, it can be confirmed that the fracture location of the tensile specimens is located at the boundary region between the inter-layer area and the inner-layer area. Meanwhile, the fracture form is typical intergranular fracture. They are mainly due to the easy generation of porosity aggregation and precipitation of a large number of theta(Al2Cu) phases in the inter-layer and inner-layer junctions.