Researchers at the University of Wolverhampton have developed 3D printable copper-silver alloys that demonstrate superior strength and heat transfer performance in comparison to those that are currently available.
The project was initiated by the increasing industry demand for 3D printable heat transfer materials and devices. The study was led by the Additive Manufacturing of Functional Materials (AMFM) research group who, part of the Centre for Engineering Innovation and Research (CEIR) at the University of Wolverhampton. The same group recently developed a 3D printable copper-tungsten-silver alloy.
Highly reflective materials such as silver and copper are known to be challenging for laser 3D printing processes. However, establishing this was significant due to the potential enhancements offered by silver and copper alloys in enabling the next generation of aerospace, automotive and biomedical devices.
Silver and copper exhibit exceptional thermal properties in comparison to other metals. Silver has the highest thermal conductivity and thermal diffusivity performance properties of any metal followed closely by copper. However, the high reflectivity and desired thermal conductive properties create challenges for laser 3D printing due to laser energy reflection and heat dissipation hindering material meltpool generation.
The research showed that the copper-silver alloys significantly outperform 3D printed pure silver, pure copper and all commercially available copper materials evaluated.
The research team, whose expertise comprise additive manufacturing (3D printing) material and process development, have been investigating combining functional materials with developments in design tools and 3D printing to create high performance 3D printable alloys and devices that show potential for healthcare, automotive, aerospace, and renewable energy applications.
Dr. Arun Arjunan, Director of the CEIR at the University of Wolverhampton, said: “Thermal management is challenging for many sectors and even small improvements in heat transfer can have a significant impact on reducing material waste while increasing component reliability and life.
“Additionally emerging systems, such as those in electric vehicles (EVs), radio-frequency systems, high power light-emitting diodes, solar cells and solid-state laser light sources, all have significant heat dissipation requirements and therefore innovative materials and advanced manufacturing technologies are essential to create effective thermal management devices of such systems.”
Project lead researcher, John Robinson, who previously worked as DMLS Development Manager at Cookson Gold, developing 3D printing laser processing parameters for precious metal alloys, added: “My previous role as DMLS Development Manager oversaw the metal 3D printing department and associated material and process development activities where we were developing laser processing parameters for gold, platinum and silver alloys. While much of my work was aimed specifically at jewelry and watch applications, I saw significant demand for sterling silver for thermal management applications.
“While industrial collaborative projects restricted the development of industrial silver-based alloys at that time, the industry demand for enhanced thermal performance materials and complex structures continued after joining the University of Wolverhampton initiating research in this area.
“As sterling silver is essentially a copper-silver alloy with 92.5% silver content, it is relatively expensive in comparison to 3D printable copper and other available 3D printing metal materials. However, for high-value applications such as aerospace and space, the enhanced performance may warrant the cost.”
Copper-silver alloys with 30% silver content demonstrated 84%, 100% and 106% higher yield strengths in comparison to commercially available copper, commercially pure copper, and copper-chromium-zirconium while ultimate tensile strength was 91%, 62% and 82% higher. Thermal diffusivity was also shown to increase by 6.2% with silver addition demonstrating the potential for the development of high-performance copper-silver alloys for heat transfer and thermal management applications.
Dr Ahmad Baroutaji, study co-author and Mechanical Engineering Course Leader at the University of Wolverhampton, further explained: “This is really the first step for the AMFM research group in custom 3D printed thermally-conductive materials and research has already begun on 3D printing of materials with exceptional electrical conductivity properties suitable for fabricating induction and electrical windings for electromagnetic applications and electric machines.
“Furthermore, with the team’s expertise in predictive modeling and crashworthiness complementing our material and manufacturing knowledge, other research projects are already investigating the potential for triply periodic minimal surface (TPMS) structures incorporating thermal management and impact protection for battery in EVs.”
Future studies will include 3D printed triply periodic minimal surface structures printed in copper-silver. The research group is also working with collaborators in establishing 3D printed high purity copper and silver with enhanced IEC electrical conductivity for electromagnetic applications.
All results reported have been peer-reviewed and accepted for publication in the Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (SAGE Publications).