Ultrahigh Strength and Ductility of Cu-Nb Nanolayered Composites
In recent years, the high strength of nanomaterials has gathered much interest in the materials community. Nanomaterials (polycrystalline and composites) have already been used, largely by the semiconductor community, as critical length scales for chip design have decreased to tens of nanometers. However, to ensure reliability of nanomaterials, the mechanisms underlying their structural integrity must be well understood. For these materials to be put into service, not only should their strength be considered, but also ductility, toughness, formability, and fatigue resistance. While some progress has been made into constructing models for the deformation mechanisms governing these behaviors, the body of experimental knowledge is still limited, especially for length scales below 10 nanometers. The results described here show stress-strain curves for nanolaminate composites with individual layer thickness of 40 nm and 5 nm. Nanolaminate composites fabricated via magnetron sputtering comprised of alternating 5 nm thick Cu and Nb multilayers (two relatively soft metals) exhibit strengths on par with hardened tool steel and deformability in compression in excess of 25% . The deformability of nanoscale composites is found to be limited by the onset of geometric instability.
Yonghao Zhao and Xiaozhou Liao
N. A. Mara et al., "Ultrahigh Strength and Ductility of Cu-Nb Nanolayered Composites", Materials Science Forum, Vols. 633-634, pp. 647-653, 2010