Abstract
The mechanical properties of selective laser melting (SLM) components are fundamentally dependent on their microstructure. Accordingly, the present study proposes an integrated simulation framework consisting of a three-dimensional (3D) finite element model and a cellular automaton model for predicting the epitaxial grain growth mode in the single-track SLM processing of IN718. The laser beam scattering effect, melt surface evolution, powder volume shrinkage, bulk heterogeneous nucleation, epitaxial growth, and initial microstructure of the substrate are considered. The simulation results show that during single-track SLM processing, coarse epitaxial grains are formed at the melt–substrate interface, while fine grains grow at the melt–powder interface with a density determined by the intensity of the heat input. During the solidification stage, the epitaxial grains and bulk nucleated grains grow toward the top surface of the melt pool along the temperature gradient vectors. The rate of the epitaxial grain growth varies as a function of the orientation and size of the partially melted grains at the melt–substrate boundary, the melt pool size, and the temperature gradient. This is observed that by increasing heat input from 250 J/m to 500 J/m, the average grain size increases by ~20%. In addition, the average grain size reduces by 17% when the initial substrate grain size decreases by 50%. In general, the results show that the microstructure of the processed IN718 alloy can be controlled by adjusting the heat input, preheating conditions, and initial substrate grain size.
Highlights
Selective laser melting (SLM) refers to the production of 3D components in a layerby-layer fashion through the selective melting of a metal powder bed
The size of Region II was set in such a way as to ensure that the system was large enough to prevent the laser heat input in Region I from reaching the system boundaries, thereby causing the boundary conditions to affect the melt pool cooling speed in an unrealistic manner
This study has presented an integrated FE-cellular automaton (CA) framework for simulating epitaxial grain growth during the single-track SLM processing of IN718 nickel alloy
Summary
Selective laser melting (SLM) refers to the production of 3D components in a layerby-layer fashion through the selective melting of a metal powder bed. 718 (IN718), which has superior mechanical properties at elevated temperatures and is widely used to fabricate many critical components in the aerospace and aircraft engine industries [1,2,3]. The final mechanical properties of SLM components are critically dependent on their microstructure [4]. The SLM process involves many complex multiphysics phenomena, such as laser–powder and laser–metal interactions, ultrafast solidification, complicated melt flows, phase transformation, and so on, where all of these phenomena have both individual and interactive effects on the final microstructure of the SLM component [5,6,7,8]. Given the complexity of the SLM process, the use of experimental trials to clarify the mechanisms underlying the microstructure evolution of the workpiece during the melting and solidification processes is extremely expensive and time-consuming. Rai et al [17] developed a 2D CA-Lattice
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