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Magnetron-sputter-deposited austenitic 330 stainless steel (330 SS) films, several microns thick, were found to have a hardness ∼6.5 GPa, about an order of magnitude higher than bulk 330 SS. High-resolution transmission electron microscopy revealed that sputtered 330 SS coatings are heavily twinned on {111} with nanometer scale twin spacing. Molecular dynamics simulations show that, in the nanometer regime where plasticity is controlled by the motion of single rather than pile-ups of dislocations, twin boundaries are very strong obstacles to slip. These observations provide a new perspective to producing ultrahigh strength monolithic metals by utilizing growth twins with nanometer-scale spacing.

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering. 304SS has a face-centered-cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the 304SS layers exhibit the fcc structure for layer thickness of ≤5 nm in epitaxy with the neighboring fcc Cu. For 304SS layer thickness larger than 5 nm, body-centered-cubic (bcc) 304SS grains grow on top of the initial 5 nm fcc SS with the Kurdjumov-Sachs orientation relationship between bcc and fcc SS grains. The maximum hardness of Cu/304SS multilayers is about 5.5 GPa (factor of two enhancement compared to rule-of-mixtures hardness) at a layer thickness of 5 nm. Below 5 nm, hardness decreases with decreasing layer thickness. The peak hardness of fcc/fcc Cu/304SS multilayer is greater than that of Cu/Ni, even though the lattice-parameter mismatch between Cu and Ni is five times greater than that between Cu and 304SS. This result may primarily be attributed to the higher interface barrier stress for single-dislocation transmission across the {111} twinned interfaces in Cu/304SS as compared to the {100} interfaces in Cu/Ni.

Synthesis and characterization of metal-dielectric composites with copper nanoparticles embedded in a glass matrix: A multitechnique approach J. Appl. Phys. 98, 054301 (2005); Nanostructured Cu/Mo multilayers were prepared by magnetron sputtering. The thickness of the Cu layer was kept constant at 0.6 nm, while the thickness of the Mo layers varied from 2.5 to 20 nm for different specimens. The Cu layers exhibit a body centered cubic ͑bcc͒ structure and the interface between Cu and Mo remains sharp and planar in all specimens. Annealing of a Cu 0.6 nm/Mo 20 nm multilayer produced three-dimensional arrays of Cu nanoparticles lying along the previous interface. These Cu nanoparticles have an average particle size of roughly 2 nm with a bcc structure. Temperature-dependent resistivity measurements in as-deposited and annealed samples are reported. These data indicate that carrier scattering changes markedly as the system evolves from one that consists predominantly of planar interfaces to one dominated by spherical scattering centers.

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering at room temperature. 304SS has a face-centered cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the SS layers exhibited fcc structure for layer thickness of less than or equal to 5 nm. For 304SS layer thickness larger than 5nm, bcc 304SS grains were observed to grow on top of the initial z 5 nm of fcc SS. The maximum hardness of Cu/304SS multilayers was z 5.5 GPa (factor of two enhancement compared to rule of mixtures hardness) achieved at a layer thickness of 5nm, with a decrease in hardness with decreasing layer thickness below 5 nm. The hardness of fcc/fcc Cu/304SS multilayers (layer thickness < 5 nm) is compared with Cu/Ni, another fcc/fcc system, to gain insight on how the mismatch in physical properties such as lattice parameters and shear moduli of the constituent layers affect the peak hardness achieved in these nanoscale systems. IntroductionNanostructured multi layers are made up of alternating nanometer scale layers of two different materials. The layer thickness can be well controlled in the scale of nmm or less by physical vapor deposition (PVD). These nanostructured multilayers have novel mechanical, electrical, magnetic, and optical properties [1][2][3]. The mechanical properties of these multilayered composites are of particular interest since the strength of these multilayer composites can be significantly increased to about 1/3 of the theoretical strength limit [4]. In the jin to the sub-[tm length scale regime, the strengthening in these multilayers can be explained by the Hall-Petch model of dislocation pile-ups at interfaces or grain boundaries. The yield strength, a, is proportional to h-1/