Ultrasound strengthens 3D printed metal alloys

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Ultrasound strengthens 3D printed metal alloys

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Liquid a alloy. The researchers deCavitation posited the alloy onto a vibrating (frequency: 20 Equiaxed Vibration grains kHz) ultrasonic stage. Powder stream Although the mechanism Deposited material was not entirely clear, Ultrasound the researchers believe sonotrode Solidification front 20-kHz vibration that the ultrasound produced tiny air bubbles in b c the molten metal during printing. Subsequently, these bubbles exploded and emitted intense and localized shock waves that impeded the growth and parallel alignment of grains, leading to fine grains aligned equally in (a) Scheme of the ultrasound-assisted 3D metal printing setup. (b and all directions. Polarized light microscope images showing the microstructures of The mechanical prop- c) Ti-6Al-4V printed (b) without and (c) with ultrasound. Credit: Nature erties of Ti-6Al-4V print- Communications. ed with ultrasound were appreciably improved over those of the conventionally 3D printadditive manufacturing....The fundamened counterpart. Tensile tests revealed that tal scientific impact of the study lies in protensile strength and yield stress both inmoting nucleation during solidification via creased by 12% compared to the same ala possible metal-independent activation of loy printed without ultrasound, reaching cavitation within the melt. The broad sci1137 ± 4 MPa and 1094 ± 18 MPa, reentific merit is in modulating ultrasound to spectively. The break of grain-orientation enable site-specific microstructural control anisotropy and reduction of the grain size in a manner unachievable by traditional both strengthened the printed alloy. metal processing.” Tertuliano was not in The technique could be adapted to othvolved in this study. er metal alloys (e.g., Ni-based superal Qian says, “We hope the idea demonloy Inconel 625) and to constructing adstrated in this article could eventually bevanced structures, such as structurally come a commercially useful process for gradient alloys. 3D printing of small metal parts. For this Ottman Tertuliano of Stanford Univerpurpose, we have just completed the desity, whose research involves nanoparticlesign of a much more powerful ultrasonic enabled metal 3D printing, says, “Manipsystem and will test the system under difulating microstructure within a complex ferent printing conditions.” architecture is the holy grail of metal Tianyu Liu

a Qian of the Royal Melbourne Institute of Technology (RMIT), Australia, and co-workers reported in Nature Communications (doi:10.1038/ s41467-019-13874-z) that applying ultrasound during three-dimensional (3D) printing of the titanium alloy Ti-6Al-4V, widely used in aerospace and biomechanical applications, could improve its mechanical strength. They determined that the mechanism of the enhancement originated from the refinement of grain size and regulation of grain orientation in the alloy by ultrasonic agitation. The use of ultrasound addressed a longlasting challenge in fusion-based, metal 3D printing—reducing the structural anisotropy of the