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Engineering    2017, Vol. 3 Issue (5) : 701-707
Research |
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Electron beam selective melting (EBSM) is a promising additive manufacturing (AM) technology. The EBSM process consists of three major procedures: ① spreading a powder layer, ② preheating to slightly sinter the powder, and ③ selectively melting the powder bed. The highly transient multi-physics phenomena involved in these procedures pose a significant challenge for in situ experimental observation and measurement. To advance the understanding of the physical mechanisms in each procedure, we leverage high-fidelity modeling and post-process experiments. The models resemble the actual fabrication procedures, including ① a powder-spreading model using the discrete element method (DEM), ② a phase field (PF) model of powder sintering (solid-state sintering), and ③ a powder-melting (liquid-state sintering) model using the finite volume method (FVM). Comprehensive insights into all the major procedures are provided, which have rarely been reported. Preliminary simulation results (including powder particle packing within the powder bed, sintering neck formation between particles, and single-track defects) agree qualitatively with experiments, demonstrating the ability to understand the mechanisms and to guide the design and optimization of the experimental setup and manufacturing process.

Keywords Modeling      Electron beam      Additive manufacturing      Powder scale     
在线预览日期:    发布日期: 2017-11-08
Wentao Yan
Ya Qian
Weixin Ma
Bin Zhou
Yongxing Shen
Feng Lin
Wentao Yan,Ya Qian,Weixin Ma, et al. Modeling and Experimental Validation of the Electron Beam Selective Melting Process[J]. Engineering, 2017, 3(5): 701-707.
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Fig.1  Experiments and models of all procedures in the EBSM process. DEM: discrete element method; PF: phase field; FVM: finite volume method.
Fig.2  Schematic of the fields in the PF model.
Fig.3  The in-house EBSM system. (a) Schematic; (b) photograph.
Fig.4  Experimental and simulation results of powder spreading. (a) Simulations can guide the design and optimization of the (b) powder rake; (c) simulation and (d) experimental results of spreading a powder layer over previous layers.
Fig.5  Powder-spreading simulation results at various rake speeds.
Fig.6  Experimental and simulation results of powder sintering. (a), (b) two powder particles with different sizes; (c), (d) two powder particles with similar sizes.
Property Value Unit
Grain boundary mobility, ϑ gb 10-11 m4·(J·s)-1
Grain boundary energy, γ gb [ 14] 0.81 J·m-2
Surface energy, γ sf [ 14] 2.1 J·m-2
Volume diffusion, Q υ [ 15] 3.2?×?10-19 J
Surface diffusion, D O υ [ 15] 2.92?×?10-19 m2·s-1
Surface diffusion coefficient, D eff s [ 16] 2?×?10-9 m2·s-1
Preheating temperature, T 1100 °C
Tab.1  Material parameters applied in the powder-sintering simulation.
Fig.7  Simulation result of an electron beam heating a spherical powder particle on a substrate. (a) Schematic; (b) simulated.
Fig.8  Experimental and simulation results of (a) and (c) balling effect; and (b) and (d) single-track non-uniformity [13].
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