Bulk nanostructured (NS) metals, with structural units falling in the nanometer range, have emerged as a new class of materials. However, fabrication of artifact-free bulk NS metals with relatively large sample size still poses a challenge, the mechanical behavior needs to be further improved to achieve better combination of strength and ductility, and the fundamental understanding requires to be enhanced of the relationship between processing, microstructure and mechanical behavior. This dissertation selected Cu and Cu alloys as model materials to study processing, microstructure, mechanical behavior and deformation mechanisms of bulk NS metals. Bulk NS Cu and Cu alloys were fabricated by equal channel angular pressing (ECAP), spark plasma sintering (SPS) of cryomilled powders, or by high-pressure torsion (HPT) of coarse-grained or cryomilled powders, in efforts to simultaneously achieve high strength and satisfactory ductility, and to deepen our fundamental understanding of the microstructure and deformation mechanisms that govern the mechanical behavior of bulk NS metals. The temperature at which ECAP is conducted was found to have significant effect on microstructure evolution and mechanical behavior of ultrafine-grained Cu processed by ECAP. A superior combination of strength and ductility was achieved when ECAP was performed at 523 K where discontinuous dynamic recrystallization induces a high fraction of equiaxed grains with a very low dislocation density. During SPS of cryomilled nanocrystalline (nc) Cu powders, the presence of very small amounts of O and N in the powders, which were introduced during cryomilling and handling, and the change of these impurities during SPS were demonstrated to significantly influence the densification response. A bulk NS Cu-Zn-Al alloy with ultrahigh strength was fabricated via SPS of cryomilled powders. The microstructure of the alloy was thoroughly characterized, and various strengthening contributions were quantified, including grain boundary, twin boundary, second-phase particle, dislocation and solid-solution strengthening, and the calculated overall strength achieved a reasonable agreement with the experimental strength. The twins in the cryomilled Cu-Zn-Al powders and sintered bulk samples were carefully investigated, in an effort to provide insight into the mechanisms governing the evolution of twins during SPS, including grain boundary migration, twin boundary migration, recrystallization and detwinning. HPT was applied to coarse-grained (CG) and nc Cu powders, with identical processing parameters. HPT of CG Cu powders resulted in exceptional grain refinement and increase in dislocation density, whereas significant grain growth, via grain rotation-induced grain coalescence, and decrease in dislocation density occurred during HPT of cryomilled nc Cu powders. Equilibrium structures were achieved under both conditions, with very similar stable grain sizes and dislocation densities, suggesting dynamic balances between deformation-induced grain refinement and grain growth, and between dislocation accumulation and dislocation annihilation.

Special topic volume with invited peer reviewed papers only

Volume is indexed by Thomson Reuters BCI (WoS). Strength and ductility are two of the most important mechanical properties of structural materials, but this usually involves a trade-off, because of the fundamental inverse proportionality of these two features. Since the 1980s, bulk nanostructured materials have emerged as a new class of material having unusual structures and, as a result, have attracted increasing attention. Unfortunately, most bulk nanostructured materials still do not evade the strength-ductility trade-off dilemma, and usually have very poor ductility. The poor ductility of bulk nanostructured materials has indeed become a seemingly insurmountable obstacle to the widespread technological application of structural bulk nanostructured materials.

Tensile strength, fatigue strength and ductility are important properties of nanostructured metallic materials, which make them suitable for use in applications where strength or strength-to-weight ratios are important. Nanostructured metals and alloys reviews the latest technologies used for production of these materials, as well as recent advances in research into their structure and mechanical properties. One of the most important issues facing nanostructured metals and alloys is how to produce them. Part one describes the different methods used to process bulk nanostructured metals and alloys, including chapters on severe plastic deformation, mechanical alloying and electrodeposition among others. Part two concentrates on the microstructure and properties of nanostructured metals, with chapters studying deformation structures such as twins, microstructure of ferrous alloys by equal channel angular processing, and characteristic structures of nanostructured metals prepared by plastic deformation. In part three, the mechanical properties of nanostructured metals and alloys are discussed, with chapters on such topics as strengthening mechanisms, nanostructured metals based on molecular dynamics computer simulations, and surface deformation. Part four focuses on existing and developing applications of nanostructured metals and alloys, covering topics such as nanostructured steel for automotives, steel sheet and nanostructured coatings by spraying. With its distinguished editor and international team of contributors, Nanostructured metals and alloys is a standard reference for manufacturers of metal components, as well as those with an academic research interest in metals and materials with enhanced properties.

Nanocrystalline copper samples were produced and analyzed with the aim of elucidating how very small grain sizes affect mechanical properties of crystalline materials. The mechanical properties and microstructure of the material were investigated. Important mechanical properties explored include yield strength, hardness, and ductility. Such microstructural parameters as grain size, grain morphology, grain size distribution, and bulk density were also evaluated. Grain size and strength in conventional metals are related by the Hall-Petch relation, which is expected to lose relevance at low grain sizes. At average grain sizes of 10--100 nm, previous researchers often noted deviations from Hall-Petch predictions of strength. In contrast, samples in the same grain size regime tested in compression were found to adhere to the relation for both yield strength and hardness in this study. At the lowest grain sizes, a mild reversal in the trend of the Hall-Petch relation may be visible, suggesting a possible shift in the dominant deformation mechanism. In addition, Transmission Electron Microscopy (TEM) was used to observe deformation of nanocrystalline copper in situ. Grains of 40 nm and perhaps smaller sizes appear to deform by dislocation motion, though other mechanisms may also be active. Extensive examinations of loose powder were also performed via TEM. Wide grain size distributions were likely to have arisen during consolidation, because uncompacted powders have a more uniform and smaller distribution. Processing of samples was controlled to achieve a variety of grain morphologies for property evaluation.

These proceedings of the "Second International Conference on Nanomaterials by Severe Plastic Deformation" review the enormous scientific avalanche that has been developing in the field over recent years. A valuable resource for any scientist and engineer working in this emerging field of nanotechnology.

The field of materials science and engineering is rapidly evolving into a science of its own. While traditional literature in this area often concentrates primarily on property and structure, the Materials Processing Handbook provides a much needed examination from the materials processing perspective. This unique focus reflects the changing comple