Achieving high performance of wire arc additive manufactured Mg–Y–Nd alloy assisted by interlayer friction stir processing

Wire arc additive manufacturing (WAAM) and friction stir processing (FSP) technologies are belong to two attractive manufacturing processes for diversified structural materials. In this study, the WAAM and FSP technologies were innovatively combined to form an advanced hybrid WAAM + interlayer FSP additive manufacturing approach, and it was applied to fabricate the multi-layer Mg–3.2Y–1.6Nd–0.5Zr (wt%) alloy thin wall. The microstructure evolution and mechanical properties of the wall were systematacially investigated. It is found that after the interlayer FSP deformation, the WAAM-deposited material grain size is refined from ∼19 µm to ∼3.5 µm at the top region of the wall, and also the coarse eutectic phases Mg24Y5 are broken into small particles and uniformly dispersed within the α-Mg matrix, resulting in improving the mechanical properties of Mg-based materials. As compared to the WAAM counterpart, the microhardness, yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the WAAM + interlayer FSP fabricated Mg–Y–Nd alloy are increased from 79.3 HV, 159 MPa, 236 MPa and 9.9 % to 88.0 HV, 207 MPa, 289 MPa and 19.8 %, respectively. However, due to the presence of inevitable thermal cycling during the additive manufacturing process, the microstructure in the middle and bottom regions of the thin wall are relatively coarsened, leading to a slight decrease in YS (∼20 MPa) as compared to that of the top region, but the UTS is remained essentially unchanged, and the EL increased to 25.7 %.