Nano Focus: Solidification technique at the nanoscale expands range of 3D-printable alloys
- PDF / 1,038,752 Bytes
- 2 Pages / 585 x 783 pts Page_size
- 12 Downloads / 165 Views
Nano Focus
applauded the improvement in the efficiency of cycling Li-metal anodes in an asphalt-graphene matrix, and felt that it would be interesting to identify the mechanism, either modifying transport or reaction kinetics, in future work. Thus, the Asp-GNR porous structure offers an interesting solution to the quest
a
for uniform, stable Li-metal electrochemistry. It simultaneously combines augmentative characteristics such as reduced electrode impedance and uniform Li electroplating. Future work relies on further improvement of such electrodes to make them a commercial reality. Aashutosh Mistry
b
Solidification technique at the nanoscale expands range of 3D-printable alloys
W
hile three-dimensional (3D) printers have been able to print metal parts for years, the process works only for a few industrially useful alloys. The vast majority of the 5500 alloys currently used cannot be additively manufactured. That could change soon thanks to researchers at HRL Laboratories, LLC in Malibu, Calif., who have developed a way to 3D print high-strength aluminum alloys. The method opens the possibility of 3D printing and welding light, strong alloys that are commonly used to make aircraft frames as well as car and truck parts. It might also lead to 3D printing of any metal. This work is reported in a recent issue of Nature (doi:10.1038/nature23894). Conventional 3D printing of metallic structures involves depositing layers of metal powders and then moving a focused laser or electron beam across the layers one at a time, melting and fusing the material together to form a solid mass. Because this fusion of metal layers is similar to welding, 3D printing works for alloys that are known to be weldable. In other alloys, such as highstrength aluminum and nickel alloys, it results in cracks that can span multiple layers. The process, called hot tearing, occurs because the grains in these alloys solidify as vertical columns, causing the alloy’s residual liquid content to get trapped between them. Later, as the solid material shrinks, the liquid film can rupture.
872
200 µm
200 µm
(a) Microstructure analysis of a 3D-printed component made with the aluminum alloy Al7075 shows large cracks; (b) when the alloy powders are coated with Zr nanoparticles before 3D printing, no cracks are observed. Credit: Nature.
Hot tearing would not happen if the alloys solidified as small grains as opposed to large columns. Scientists have tried in the past to disrupt column growth and create a granular microstructure by changing things like the 3D printing speed or the power of the laser. But that does not provide the scientists enough control over the microstructure. So John H. Martin and his colleagues at HRL Laboratories turned to an old strategy used in metal casting, where additives are commonly mixed into liquid metals to act as seeds for crystals to grow. The researchers coated alloy powders with hydrogen-stabilized zirconium nanoparticles and then used lasers to heat them. As the metal cools and solidifies, it follows the crystallin
Data Loading...
