Abstract
The prediction of solidification microstructures associated with additive manufacture of metallic components is fundamental in the identification scanning strategies, process parameters and subsequent heat treatments for optimised component properties. Interactions between the powder particles and the laser heat source result in complex thermal fields in and around the metal melt pool, which will influence the spatial distribution of chemical species as well as solid-state precipitation reactions. This paper demonstrates that a multi-component, multi-phase precipitation model can successfully predict the observed precipitation kinetics in Inconel 625, capturing the anomalous precipitation behaviour exhibited in additively manufactured components. A computer coupling of phase diagrams and thermochemistry (CALPHAD)-based approach captures the impact of dendritic segregation of alloying elements upon precipitation behaviour. The model was successful in capturing the precipitation kinetics during annealing considering the Nb-rich and Nb-depleted regions that are formed during additive manufacturing.
Highlights
The manufacture of nickel-based superalloy components through powder-bed selective laser melting (SLM) is challenging
This has proven to be a major issue in the additive manufacture (AM) of γ strengthened superalloys where uncontrolled precipitation of the intermetallic phase will lead to reduced ductility
The dislocation density in the AM condition was approximated by the steady-state dislocation density
Summary
The manufacture of nickel-based superalloy components through powder-bed selective laser melting (SLM) is challenging. Variations in chemical compositions between the interdendritic zones and the truck of dendrites will lead to heterogeneous distributions of precipitates after the application of subsequent heat treatments. This has proven to be a major issue in the additive manufacture (AM) of γ strengthened superalloys where uncontrolled precipitation of the intermetallic phase will lead to reduced ductility. Precipitation during AM will influence the mechanical response and the development of component distortions and residual stresses. The ability to predict location specific microstructure variations is important in both understanding and predicting component properties following post-build heat treatments and in-service response. Precipitation models can be used to guide and optimise heat treatments and predict the evolution of Zener pinning precipitates during grain growth
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