Ultrasound tailors grain structure in metal 3D printing
Ultrasound tailors grain structure in metal 3D printing lead image
As one important type of additive manufacturing, directed energy deposition (DED) can modify metals point by point. The technique acts as a complex 3D printer, melting existing material and depositing new metal simultaneously. This introduces the ability to create hierarchal structures, increasing mechanical performance.
However, DED is not favorable in many applications because of its resultant anisotropy. The grain structure changes throughout the metal, and the mechanical properties therefore differ depending on direction.
Yang et al. explored how ultrasound-assisted direct energy deposition (UADED) can tailor grain size and enhance mechanical properties in 3D printed metals. The team conducted high speed imaging observations, and, for the first time, simulated how the ultrasound influences the molten pool dynamics.
“Applying ultrasound in the manufacturing process has existed for many decades. It works, but people don’t know how or why it works, particularly in additive manufacturing,” said author Wentao Yan. “Our motivation was to understand that. Further, we want to know how we can better control it.”
By closely examining the impacts of the ultrasound, the researchers developed a hybrid deposition strategy that minimizes defects and produces a microstructure with alternating but consistent grain sizes.
Their model replicated the observations very well and could replace physical trial-and-error experiments in the future. This would reduce the cost and time to test new materials, machines, and manufacturing parameters.
In the future, the group aims to examine how ultrasound could assist other additive manufacturing technologies. They believe the broad methodology of adding an external field, like ultrasound or a magnetic field, to an existing printing technique could allow for further material control.
Source: “Manipulating molten pool dynamics during metal 3D printing by ultrasound,” by Zhichao Yang, Shuhao Wang, Lida Zhu, Jinsheng Ning, Bo Xin, Yichao Dun, and Wentao Yan, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0082461 .
