Strengthening of 3D printed Cu micropillar in Cu-Ni core-shell structure

• Published in: Materials & design 2023-03, Vol.227, p.111717, Article 111717
• Main Authors: Jain, Manish, Sharma, Amit, Schürch, Patrik, Ventura, Nicolo Maria Della, Koelmans, Wabe W., Maeder, Xavier, Schwiedrzik, Jakob, Michler, Johann
• Format: Article
• Language: English
• Subjects: 3D printing; Additive micromanufacturing; Core–shell structure; In-situ micromechanics; Nanocrystalline Ni
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2023.111717

[Display omitted] •Copper (Cu) micropillars were fabricated using additive micromanufacturing and subsequently coated with Nickel (Ni) to create Cu-Ni core–shell structure.•In-situ micropillar compression revealed an exceptional ∼ 3-fold increase in strength after coating the Cu structure with a Ni shell.•Experiments and FE simulation showed remarkable similarities in mechanical response and strengthening mechanism of Cu-Ni Direct printing of complex 3D structures at the nano- and microscale is a promising technique for MEMS devices, small-scale sensors, and actuators. So far, most studies have been focused on printing copper (Cu) structures due to the high Coulombic efficiency compared to other conductive metals such as platinum. However, Cu suffers from low material strength, low modulus, and high strain-rate sensitivity. This work introduces a unique Cu-Ni core–shell structure for improved strength. A 3D additive-micromanufacturing technique based on localized electrodeposition was utilized to fabricate dog-bone-shaped Cu micropillars with submicron resolution. These pillars were subsequently coated with Ni by pulse-reverse electrodeposition. A combination of in-situ micropillar compression at various strain rates (0.001–500 s−1) and finite element simulations revealed remarkable strengthening in the Ni-coated Cu micropillar. Data obtained from both experiments and simulations were in good agreement, suggesting the strengthening was dominated by interface characteristics, stress redistribution, and geometrical effects. Furthermore, the study demonstrates that shape and dimension of the 3D-printed objects can be retained while increasing their strength drastically. These findings can be extended to other material systems and provide a pathway to develop strong and tough composites and metamaterials at multiple length scales for future applications.