Compared with subtractive manufacturing, the unique advantage of additive manufacturing is that it is easier to process metals and has the added benefit of producing unique geometrical parts. In addition to opening up to handle difficult-to-process materials (such as refractory metals), additive manufacturing also makes metal matrix composite processing (MMC) possible. A study published in the Chinese Journal of Mechanical Engineering recorded the method of 3D printing MMC used by a research team to combine the different properties of metal and reinforcing fibers.
Researchers from the Shaanxi Rapid Manufacturing Technology Engineering Research Center combined tin-lead with carbon fiber to explore the possibility of using lead’s radiation shielding properties on the one hand and the strength of carbon fiber on the other. At the same time, this study attempts to demonstrate the 3D printing capabilities of lead, which was previously difficult to achieve due to the wettability of lead (it cannot stick to a solid surface in a liquid state).
To achieve this goal, the research team relied on liquid tin lead with better wettability. Through a process called Fiber Traction Printing (FTP), carbon electroplated with nickel and copper is fed into the extruder, and then immersed in molten tin-lead, using existing composite 3D printers similar to Markforged and Anisoprint Material extrusion process for printing.
Researchers have made many observations on this technology. For example, due to the surface tension of liquid metal, researchers cannot theoretically calculate how to achieve morphological uniformity. However, the team was able to determine the actual relationship between printing speed and deposition uniformity. Although carbon fibers with a higher degree of electroplating show no observable defects, the wettability between the liquid metal and the fibers is also low, and the coating is thicker.
Studies have shown that by combining liquid metal with carbon fiber, not only can the liquid metal be molded into the desired shape, but also the mechanical properties of low melting point alloys (such as tin-lead) can be improved. When using carbon fiber with a 3 micron electroplated layer, the tensile strength of the tin-lead material increased from 33.3 MPa to 235.2 MPa. As the thickness of the plating layer increases, the fiber volume also increases.
The function of 3D printing lead may lead to unique parts that require radiation shielding, such as spacecraft. The team believes that the FTP process can be extended to other MMCs, such as carbon fiber aluminum and carbon fiber magnesium.
Since metal matrix composites are almost always more expensive than the traditional materials they replace, they are usually only used for high-end applications, such as high-performance tools (tungsten carbide), sports cars (carbon fiber and silicon carbide, boron aluminum), electronic products ( Copper silver and diamond, aluminum graphite), and aerospace (silicon carbide fiber and titanium). Similarly, due to scale issues, additive manufacturing is often reserved for high-end short-term applications. In turn, with the improvement of printing MMC capabilities, we expect that these two areas may have greater overlap.
So far, many institutions are conducting research on printing MMC, including California State University, where a team is 3D printing titanium alloys with ceramics. AGH University, combined Inconel625 and tungsten carbide; Deakin University (Deakin University), combined boron nitride and titanium.
Although this type of research naturally takes time to transcend the limits of the laboratory, there is no doubt that existing commercial entities are likely to be researching similar technologies, especially if these companies are already dealing in fiber composite materials and metals, like DesktopMetal Same as Markforged.