Structural design of a coaxial-jet vortex powder mixer for multi-material directed energy deposition.

Directed energy deposition (DED) offers an unprecedentedly convenient and efficient additive manufacturing approach for novel alloy design. As a critical component of the novel DED system, a powder mixer plays an important role in the stable and uniform mixing of different powders. In this work, the coaxial-jet dome powder mixer (CDPM) was designed based on the convergent-jet cone powder mixer (CCPM). In order to explore a reliable multi-powder mixing mechanism, the gas-solid two-phase flow state in the mixing chamber was simulated by the large eddy simulation and discrete particle model (LES-DPM) method. In addition, the powder delivery stability and mixing uniformity of the mixer were characterized by curve fitting and image processing methods. Finally, CDPM avoids the generation of ineffective vortices that occurred in the mixing chamber. In addition, deposition experiments show that the powder mixer can ensure the uniform distribution of multiple elements in the local forming zone. [Display omitted] • Additive manufacturing gives more freedom to design multi-powder mixer. • The synchronization of atomization and mixing enables the powder to mix fully. • Vortex mixing mechanism links structural details to multi-powder mixing effects. • The well-designed mixing chamber avoids the generation of invalid vortex. • High-speed photography results reveal effective vortex mixing principle. [ABSTRACT FROM AUTHOR]