5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Laser metal deposition is an additive manufacturing technique for fabricating complex metal components layer by layer. The complex thermal behavior during this process results in the complex microstructure evolution, which directly affects the final mechanical properties of the products. Numerical modeling offers a cost efficient way to better understand the related complex physics in laser metal deposition process. It helps to reveal the effects of processing parameters on the desired characteristics of deposition parts. In this work, a heat transfer finite element model is coupled with a multi-phase-field model to predict the thermal behavior and solidification microstructure evolution during laser metal deposition process. The thermal behavior during single-track and multi-track deposition process was simulated numerically by using a three-dimensional transient finite-element model, where deposition of material was modeled through activation of a new set of elements within each solution step. The deposition geometry was well predicted without assuming a prior shape. The influences of the scanning speed and laser power on the morphology and dimensions of molten pool were investigated. It is found that the molten pool height decreases with the increase in the scanning speed, while the increase of laser power results in the increase of molten pool size. The temperature history extracted from the macro simulation was then transferred to a micro region inside the mushy zone of the molten pool, where dendrite growth during solidification was simulated by the multi-phase-field model. The effects of several process parameters on the solidification microstructures were investigated. Directional dendritic growth from the bottom of the pool was observed with various dendrite arm spacing and orientation depending on the location in the pool. The microstructure and the value of dendrite arm spacing obtained in simulation agree well with previous experimental observation.