Multi-component and multi-phase-field modelling of solidification microstructural evolution in Inconel 625 alloy during laser powder bed fusion additive manufacturing

Abstract

Inconel 625 alloy, known for exceptional mechanical properties and corrosion resistance, is widely used in aerospace, power generation, and marine applications. Laser powder bed fusion (LPBF) excels in manufacturing complex geometries with good surface finish. However, LPBF printed microstructure is highly heterogeneous due to the rapid and complex thermal cycles, necessitating careful parameter selection to prevent the stabilisation of detrimental phases. Experimental parametric optimisation of LPBF is challenging due to the cost and complex inter-playing process variables. Therefore, mathematical modelling is advantageous for optimising LPBF parameters. A 3D heat source model was developed using finite element method (FEM) to analyse thermal cycles with bed-preheating and varying laser parameters in LPBF of IN625. The model focused on a simplified thermal cycle method, where all elements in a layer were set to melt at once to reduce the computational time. A multi-phase-field method (M-PFM) was developed to simulate the microstructural evolution as a function of FEM-generated thermal boundary conditions. The morphological and elemental segregation behaviour of evolving microstructure was simulated. The dendrite morphology predicted by simulations showed strong agreement with experimental observations. The primary dendritic arm spacing (PDAS) obtained from phase-field and analytical models matched the experimental trends, validating the adapted modelling approach. The segregation and the microstructural evolution were found to be strongly influenced by the prevailing temperature gradients and the cooling rates of the melt pool, along with the peak temperatures reached during the remelting cycles.