Ultrasound-assisted direct energy deposition (UADED) attracts increasing attention due to its capability to tailor the grain structure. However, the involved molten pool dynamics, particularly the complex interaction of ultrasound-flow-solidification, remain unclear to date, which hinders quantitative prediction and regulation of the microstructures and mechanical properties of UADED components. Here, in situ high-speed imaging and high-fidelity multi-physics modeling are leveraged to investigate flow characteristics and liquid-to-solid transformation in UADED for Inconel 718. The inertial force activated by ultrasound is revealed to drive the molten pool to flow forward and backward along the vibration direction, resulting in poor surface quality. A hybrid deposition strategy is developed to minimize ultrasound-induced defects and produce superior microstructure with alternating coarse- and fine- grains. Such a layered microstructure results in 28% and 15% improvement in the yield strength and ultimate tensile strength compared to the counterpart by additive manufacturing without ultrasound. This work provides unprecedented understanding into the molten pool dynamics in the UADED process as well as valuable guidance to manipulate molten pool flow.

中文翻译：

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通过超声波控制金属 3D 打印过程中的熔池动力学

超声辅助直接能量沉积 (UADED) 因其能够调整晶粒结构而受到越来越多的关注。然而，涉及的熔池动力学，特别是超声波-流动-凝固的复杂相互作用，迄今为止仍不清楚，这阻碍了 UADED 组件的微观结构和力学性能的定量预测和调节。在这里，利用原位高速成像和高保真多物理场建模来研究 UADED 中 Inconel 718 的流动特性和液体到固体的转变。揭示了超声波激活的惯性力驱动熔池流动沿振动方向前后移动，导致表面质量差。开发了一种混合沉积策略，以最大限度地减少超声波引起的缺陷，并产生具有粗晶粒和细晶粒交替的优异微观结构。与没有超声波的增材制造相比，这种分层微结构导致屈服强度和极限抗拉强度分别提高了 28% 和 15%。这项工作为 UADED 过程中的熔池动力学提供了前所未有的理解，并为操纵熔池流动提供了宝贵的指导。