ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2024 48 3D PRINTSHOP PRINTED ALLOY TAILORED FOR SPACE A new high-performance metal 3D-printed alloy shows exceptional mechanical performance at extreme cryogenic temperatures, proving its potential for space and extreme environment applications. Researchers from the Korea Institute of Materials Science (KIMS), in collaboration with Gyeongsang National University, and Pohang University of Science and Technology (POSTECH), added a small amount of carbon to CoCrFeMnNi alloy, which exhibits excellent properties in cryogenic conditions. This alloy powder was then processed using laser powder bed fusion (LPBF). This allows maximizing the strengthening effect of the carbon addition to the alloy via finely distributed nanocarbides at the boundaries of the nano-sized cell structure. As a result, the team achieved a combination of tensile strength and ductility that was over 140% better than carbon-free alloys in cryogenic environments. In particular, the elongation of the alloy is twice as high at 77 K compared to 298 K. This technology also offers a potential guideline for new alloy design in additive manufacturing to produce high-performance products with excellent load- bearing capacity for use in cryogenic applications. Another key distinction of this technology is its ability to finely control microstructure through additive manufacturing. The researchers say the technology can be applied to complex components such as injectors that spray fuel in space exploration rockets, and turbine nozzles that extract energy. It enhances the performance and extends the lifespan of parts used in space and other extreme environments. Moreover, it overcomes the limitations of low-temperature toughness in existing 3D-printed alloys. www.nst.re.kr/eng/ contents.do?key=177. SOLVENT-FREE POLYMER FOR DIGITAL LIGHT PROCESSING Researchers at Duke University developed a low-viscosity material for digital light processing (DLP) that doesn’t require the use of a solvent for dilution. Resins typically used in DLP are solids or too viscous and require a solvent to dilute them to the right consistency. But adding these solvents also causes significant drawbacks, such as poor dimensional accuracy after printing due to part shrinkage (up to 30%) coupled with residual stress that occurs as the solvent evaporates. In addition to eliminating the shrinkage problem, the lack of solvent in this new polymer also results in improved mechanical properties of the part while maintaining the ability to degrade in the body. “I wanted to create an inherently thin, low-viscosity material for DLP to use for degradable medical devices,” says Maddiy Segal, a Ph.D. candidate working at Duke. “It took a lot of attempts, but eventually I was able to identify optimal monomers and a synthetic technique to create a solvent-free polymer that can be used in a DLP printer without any dilution.” Upon testing the properties of parts made with the polymer, she discovered that the test parts did not shrink or distort at all, and in general, they were also stronger and more durable than those made with solvents. Segal’s goal with this work is to apply this technique to biodegradable medical implants. Devices fabricated from this material could be implanted and designed to degrade naturally over time, eliminating the need for additional surgeries to remove the device. It could also potentially be used as a bone adhesive to hold fractures together temporarily or in soft robotics applications, where a soft, degradable material is needed. duke.edu. A new metal alloy can be tailored by controlling micro- structure and process parameters. Courtesy of KIMS. A toy boat printed with the new solvent-free resin through digital light processing, demonstrating the details made possible through the new material. Courtesy of Duke University.
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