Comparative study on the microstructure, mechanical properties and fracture mechanism of wire arc additive manufactured Inconel 718 alloy under the assistance of alternating magnetic field

In this study, the microstructure, mechanical properties and fracture mechanism of wire arc additive manufactured Inconel 718 alloy fabricated by cold metal transfer process under the action of the alternating magnetic field (AMF) are studied by changing the excitation current. The results show that the AMF deflects the droplet and changes the direction of the molten pool maximum temperature gradient, which inhibits the growth of large columnar crystals and refines the grains so that the index of {100}<001> texture decreases significantly. The microstructure of the 0 A and 40 A samples is composed of γ(Ni) + (TiN) [nucleus]/(NbC + TiC)[shell] + NbC + Laves. The length of γʹʹ-Ni 3 Nb of the 0 A sample (98 nm) is greater than that of the 40 A sample (84 nm). The AMF suppresses the large columnar crystals, and the average grain size is reduced to 161 μm. The volume fraction of the Laves phases is significantly reduced from 2.4% to 1.3%, and the Laves phases morphology changes from long stripe to granular under the action of the AMF. AMF increases the ultimate tensile strength and decreases the anisotropy.