High strength and high electrical conductivity bulk Cu

Abstract

The achievement of both high strength and high electrical conductivity in bulk materials is challenging in the development of multifunctional materials, because the majority of the strengthening methods reduce the electrical conductivity of the materials significantly. At room temperature, dislocations have little scattering effect on conduction electrons. Thus, a high density of dislocations can strengthen conductors without significantly increasing the resistivity. However, at room temperature (RT), which is defined as 295 ± 2 K in this paper, deformation can only introduce a limited number of dislocations in pure metals due to dislocation annihilation, i.e. recovery. This limitation is expanded by a well-controlled liquid nitrogen temperature (LNT), which is defined as 77 ± 0.5 K in this paper, deformation process that permits accumulation of both nanotwins and a high density of dislocations accompanied by significantly less recovery than that in RT-deformed samples. The dislocations are organized into refined dislocation cells, with thicker cell boundaries in LNT-deformed samples than those deformed at RT. LNT deformation stores more energy in the material than RT deformation. LNT deformation produces bulk pure Cu with a yield strength about 1.5 times that of RT-deformed Cu. The RT resistivity increase is less than 5% compared with that of annealed Cu.

Acknowledgements

We thank M. Haslow for assistance with the tests and fabrications, Y. Xin, P. N. Kalu, H. J. Schneider-Muntau and S. W. Van Sciver for discussions, and J. L. Smith for editing and comments. This work was funded by an In-House-Research-Program and carried out at the National High Magnetic Field Laboratory (NHMFL) under cooperative agreement DMR-0084173. The microscopy facilities are supported by National Science Foundation grant No. DMR-9625692 and Magnet Science and Technology at NHMFL.