How do you balance strength, ductility, electrical conductivity, and thermal stability of copper?

by Morris Wang (UCLA)

Thursday Nov 6, 2025, 3:00 PM → 4:00 PM America/Chicago

Abstract: 

Materials scientists often have to deal with multiple material science dilemma; e.g., strength –ductility trade-off, strength – electrical conductivity trade-off, and strength – thermal stability trade-off. Material strength is known to be dictated by the underlying microstructure length scale and defects, which can be quite complex and difficult to interpret. Nevertheless, almost all strengthening mechanisms reported in the literature inevitably lead to a trade-off in other important physical properties. Using copper as an example (due to its critical need in modern electrification and bright beam applications), we will discuss useful strategies to overcome the above trade-offs developed in our lab over two decades. The examples will cover nanocrystalline(average grain size < 100 nm), nanotwinned (average twin spacing < 100 nm), and nanocrystalline-nanotwinned metals (formed at the intersection of nanocrystalline and nanotwinned materials). Our experimental results demonstrate that nanocrystalline copper can be incredibly strong but often exhibits poor electrical conductivity and limited ductility. On the other hand, nanotwinned copper can exhibit incredibly balanced strength, electrical conductivity, and thermal stability. We will discuss our recent efforts to develop nanotwinned copper for electronic packaging applications. Finally, we will discuss the intriguing and tunable mechanical properties of copper fabricated by additive manufacturing techniques (AKA, 3D printing)