The microstructure and property evolutions of Inconel718 lattice structure by selective laser melting

Nickel-based lattice materials possess excellent mechanical properties and can be utilized in the fabrication of diverse lightweight structural materials, holding great potential for applications in the aerospace and automotive sectors. This study focuses on the preparation of Inconel718 lattice structure through selective laser melting and investigates the influence of heat treatment (standard heat treatment, homogenization heat treatment, and homogenization + standardization heat treatment) on the microstructure and properties of the alloy. Inconel718 is a precipitation-strengthened, high-temperature nickel-based alloy. The results indicate that the compressive properties of the lattice structures were significantly improved through homogenization heat treatment (the compressive property and energy absorption capacity were increased by 21.8% and 40.4%, respectively). This enhancement can be attributed to the dissolution of a considerable amount of δ phases (Ni₃Nb) and Laves phase ((Ni,Cr,Fe)₂(Nb,Mo,Ti)) as the solution temperature increased, thereby releasing the strengthening phase-forming element Nb. These Nb elements diffuse uniformly at a high solution temperature, and a large number of nano-sized γ″ phases (Ni₃Nb) are precipitated in the alloy grains, playing a role of dispersion strengthening and making the strength increase significantly. Moreover, after homogenization heat treatment, the dislocation density is decreased, the crack sensitivity is decreased, and the toughness of the alloy is increased. Consequently, homogenization heat treatment facilitates the dispersion, which thus strengthens the alloy and enhances its compression performance. This study holds significant theoretical and practical implications as it contributes to the advancement of fundamental research on porous high-temperature nickel-based lattice structure and broadens their range of applications. Graphical Abstract: (Figure presented.) The SLMed Inconel718 lattice structure after homogenizing heat treatment has better mechanical properties due to the precipitation of nano-sized γ″ phase.