Xiaoxu Chen, Xianhang Lu, Weiyi Deng, Shuowen Meng, Yuanhua Xie, Duchun Ba, Kun Liu, Northeastern University, Shenyang, China
In the electron beam evaporation process, parameters such as power and scanning pattern are configured to shape the beam, which then acts on the coating material. This interaction causes localized non‑uniform heating, resulting in phase transformation and subjecting the material to extreme thermal stress, thereby inducing internal cracks or micro‑voids.¹ Simultaneously, the flow of the liquid phase further exacerbates the non-uniformity of temperature distribution. These factors collectively interfere with the evaporation process and ultimately affect the uniformity of the deposited film. Therefore, investigating the influence of electron beam parameters on the phase transformation process is crucial for improving the uniformity of temperature distribution. To explore the effects of beam parameters on the phase transformation behavior of the coating material, this study employs aluminum as the material and adopts the enthalpy-porosity method for simulation. Rather than explicitly defining the solid‑liquid interface, this approach models the phase transition via a mushy zone, where the fluid state is characterized by the variation of liquid fraction, and the mushy zone is treated as a porous medium. By introducing a Darcy damping source term into the momentum equation to suppress velocity, the method enables simultaneous simulation of heat transfer and phase‑interface evolution on a fixed grid.² A comparative analysis of the complete phase transformation time under varying power levels and scanning modes (linear scanning vs. raster scanning) shows that as the power continues to increase, the phase transformation duration decreases from 200 s to 9 s, but this reduction does not follow a linear trend. This nonlinear behavior is attributed to the enhanced temperature gradient within the molten pool, which intensifies both Marangoni convection and buoyancy-driven thermal redistribution. Simultaneously, the marked increase in evaporative and radiative heat losses leads to a saturation in temperature rise, thereby diminishing the effectiveness of further power increases in accelerating phase transformation. Compared with linear scanning, the raster scanning mode achieves a shorter transformation time due to its larger effective heating area and yields a more uniform temperature distribution, which can better improve film uniformity.
Funding: The LiaoNing Transplant with Soil Program of Revitalization Talents Plan (XLYC2204011).
References:
1. 1. Y. C. Zhou, Z. P. Duan, X. H. Yan. “Thermal stress wave and spallation induced by an electron beam” International Journal of Impact Engineering, 19(7), 603-614(1997).
2. V. R. Voller, C. Prakash. “A fixed grid numerical modeling methodology for convection diffusion mushy region phase-change problems” International Journal of Heat and Mass Transfer, 30(8), 1709-1719(1987).