Dendrite growth simulation during solidification in the LENS process

A two-dimensional model combining the finite element method and the cellular automaton technique was developed to simulate dendritic growth occurring in the molten pool during the laser-engineered net shaping (LENS) process. Based on the simulation results and previously published experimental data, empirical expressions describing the relationship between the cooling rate and the dendrite arm spacing (DAS) were proposed. In addition, the influence of LENS process parameters, such as the moving speed of the laser beam, the layer thickness and the substrate size, on the DAS was also discussed. Finally, different dendrite morphologies calculated at different locations were explained based on local solidification conditions. The simulation results showed good agreement with previously published experiments. This work contributes to the understanding of microstructure formation and the resulting mechanical properties of LENS-built parts as well as providing a fundamental basis for optimization of the LENS process. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.