View article

Laser surface engineering has been employed to mimic the microstructural evolution during laser-based additive manufacturing of Alloy 718, specifically when the layers are successively fused and solidified. The micro-segregation of alloying elements in the fusion zone of laser surface melted Alloy 718 samples has been found to have a strong influence on the local precipitation behavior. The dendritic structure produced by rapid melting and solidification has shown three distinct zones – a) the core and b) the periphery of dendrites, and c) the inter-dendritic channel. While precipitation of γ’ [Ni₃(Al, Ti, Nb)] dominates in the core, the periphery is decorated by γ” [Ni₃(Nb, Mo)] and composite γ’/γ” precipitates, all in the austenite(γ) matrix. The inter-dendritic channel, rich in Nb, Mo, and C, contains discretized aggregates of Laves phase and carbides, which act as preferential nucleation sites for the equilibrium δ phase …