Microstructure evolution of wire-arc additively manufactured 2319 aluminum alloy with interlayer hammering

The cold metal transfer (CMT) based wire-arc additive manufacturing (WAAM) technology has been widely recognized as a suitable method for fabricating large-sized aluminum alloy components. However, the poor mechanical properties of the as-deposited aluminum alloys prevent their wide application in the aerospace industry. In this paper, three categories of samples with different interlayer deformation strains were fabricated by WAAM. These samples were further investigated to evaluate the effects of interlayer deformation on the mechanical properties, microstructural evolution, and the underlying strengthening mechanism. The grain size distribution and internal sub-microstructure were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). As compared to the as-deposited samples, the yield strength and ultimate tensile strength of the 50.8% deformed sample increased from 148.4 to 240.9 MPa and from 288.6 to 334.6 MPa, respectively. The microstructure of the samples with interlayer hammering exhibited highly refined grain, which is a combined result of deformation and subsequent intrinsic in-situ heat treatment induced by the next deposition layer. The recrystallized grains can be further deformed with subsequent hammering, which leads to an increase in dislocation density and contributes to an increase in ultimate tensile strength of the additively manufactured 2319 aluminum alloys with interlayer hammering.