Abstract
Based on powder-bed fusion, a coupled cellular automata (CA) approach to simulate the microstructure and concentration distribution of two different materials, stainless steel S316 L and nickel base alloy CM247LC, in the middle and high scan speed range is presented. Local non-equilibrium models for rapid solidification are considered in this study and described. The simulation outputs from S316L and CM247LC are qualitatively and quantitatively compared with each other and validated with experiments in case of S316L. The melt pool geometry defines the grain morphology. Thin columnar grains and therefore a larger number can be found in the case of CM247LC compared to S316L. The temperature history, cooling rates and diffusivities have a tremendous impact on the grain morphology, based on SLM microstructure cross-section and single crystal simulations. Furthermore, concentration maps are analysed for both materials. In case of CM247LC, concentration maps are suggested as a possibility to predict hot cracks. Temperature dependent diffusivity coefficients and atomic spacing parameters are suggested. Simulations and experimental results are in good agreement.
Highlights
Additive manufacturing (AM) processes, such as selective laser melting (SLM), were fast growing research fields in recent years
The grain size measurement is based on the Heyn lineal intercept procedure (HLI), as explained in [51]
The simulation outputs for two different scan speed parameters, in the middle and high range, are qualitatively and quantitatively compared with the two materials
Summary
Additive manufacturing (AM) processes, such as selective laser melting (SLM), were fast growing research fields in recent years. The common SLM parameters are of interest, such as laser power, scan speed, hatch distance and layer thickness, and melt pool resulting properties and the microstructure evolution itself. To predict the microstructure for single and multi-tracks of aluminium alloy AlSi10Mg, a model with coupling the heat transfer and moving melt pool using the CA approach was developed in [11]. Except the Laser-grain angle, which was quantified for three slow scan speed parameters in the range between 120 and 280 mm/s, the simulation results were qualitatively compared to experimental results from [18]. Single track CA microstructure simulations of nickel base alloy CM247LC are presented for the first time, quantified and compared to widely used stainless steel 316 L (1.4404), including two process parameters in the middle and high scan speed range. Since casting and tooling are expensive processes and limited with respect to freedom of design, aero engine manufacturers intend to establish the selective laser melting powder-bed technology [21]
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