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The instrumented nanoindentation test is used to investigate the mechanical properties and deformation behaviors of copper with different grain sizes. The results have shown that the critical shear stresses for the initiation of plastic deformation in the copper specimens with large grain sizes are close to the theoretical value and comparatively much lower for electroless copper films with an ultrafine grain size.

Molecular dynamics simulations are used for examining the mechanical deformation of bicrystalline metallic nanowires with different interfaces. The impact of interfacial microstructure on the mechanical behavior is elucidated by exploring the stress-strain property and the stress concentration along the tensile direction.

Several deformability measurements are conducted to explain the impact of the superimposed ultrasonic vibration on the plastic deformation of the pure polycrystalline Cu. An increase in the ultrasound (US) power is shown to highly increase the residual softening effect of the system.

Creep tests are conducted on a nanocrystalline Cu at room temperature and the results at very low strain rates are consistent with Coble creep. The stress-strain rate behavior of the nanocrystalline Cu has shown that as the strain rate decreases, the deformation mechanism has changed from predominantly dislocation activity to diffusion Coble creep, as observed by the strain rate sensitivity on stress and activation volume.

Severe plastic deformation processing of metals has created bulk nanostructured materials with a hierarchy of internal interfaces. Nonequilibrium grain boundaries, nonequilibrium triple junctions and microvoids/microcracks have made the percolating network of ultrafast diffusion channels, which has represented a newly recognized feature of severely deformed materials.

The large-scale molecular-dynamics simulations of dynamic deformation under biaxial tensile strain of prestrained single-crystalline nanometer-scale-thick face-centered cubic (fcc) copper films are described. The results have shown that stacking faults have played a major role in the dissociation, cross slip and eventual annihilation of dislocations in small-volume structures of fcc metals.

Nanoindentation creep tests are performed in the depth range from about 28 to 190 nm on nanocrystalline (NC) and ultrafine grain (UFG) Cu films to observe pronounced indentation size effects on hardness, creep strain rate ([epsi]), and strain rate sensitivity ([m.sub.c]). The creep deformation of NC and UFG Cu are found to be dominated by grain-boundary-mediated process and diffusion along the interface of tip sample, respectively, under a critical [h.sub.c].

Different dislocation processes observed for copper and iron operative under high rate loading by impact-induced shock tests as compared with shockless isentropic compression experiments (ICEs) are described. The extensive shock measurements observed for plate impact tests in iron are also explained in terms of plasticity-control via the nucleation of deformation twins at the propagating shock front.

A pulse electric brush-plating technique is used for synthesizing bulk nanocrystalline-Cu (nc-Cu) and the effect of strain rate on the plastic deformation behavior of this nc-Cu is examined. The results have provided insight into the transition and unusual compressive behavior of nc-Cu due to its fine and uniform grain structure and predominant high-angle grain boundaries (GBs).

The effect of deformation sequence and history on the inelastic response of copper interfaces on the nanoscale is examined. The confinement of path-history dependent material behavior within a finite layer of deformation around the bicrystal interface is observed.