Simultaneous increase of the ductility and strength of bulk ultra‐fine‐grained (UFG) Cu is achieved by introducing large amounts of deformation twins and high‐angle grain boundaries via cryodrawing and cryorolling (red plots and image). Bulk UFG materials usually have high strength but disappointingly low ductility. Most previous attempts to enhance the ductility of single‐phased UFG materials sacrificed their yield strength. This work provides a new approach for increasing ductility without sacrificing strength.

Bulk nanostructured (NS) materials have relatively high strength but disappointingly low tensile ductility (elongation to failure) at ambient temperatures. [1][2][3][4] The limited ductility of NS materials has emerged as a particularly challenging issue in the study and application of this novel class of materials. Recently, a variety of strategies aimed at improving the poor ductility of NS materials have been reported; the results reveal varying degrees of success. [5,6] Despite some encouraging reports, the improvements in ductility remain quite limited, usually below 15% for most of the strategies, except possibly for bi-modal Cu (with a ductility of 65%) and ultrafine grained (UFG) Fe-Cr-Ni-Mn steel (ca. 30%). [7,8] In this Communication, we use cryomilling and subsequently quasi-isostatic (QI) forging processes (formerly known as Ceracon forging), to prepare bulk dense multimodal and bimodal NS Ni with tensile ductility of 42% and 49%, and yield strengths of 457 and 312 MPa, respectively. This combination of strength and ductility is much superior to those of the NS Ni prepared by electro-deposition (ED), [9][10][11][12][13][14][15][16] cryorolling, [17] equal-channel angular pressing (ECAP) and high pressure torsion (HPT) methods, [18] and cold drawing. [19] Microstructural analyses suggest that significantly reduced extrinsic processing artifacts, the presence of equilibrium high-angle grain boundaries (including twin boundaries), and multi-/bimodal grain size distributions are responsible for the measured high ductility. The high strength is argued to originate from several sources, including a high density of dislocations, UFGs, and from solid solution strengthening. Compared with other synthesis methods, the synthesis methodology described in the present work has no scale or material limitations, and therefore has important implications in terms of its potential for the large-scale fabrication of bulk NS metals, alloys, and composites that can be used in applications requiring both high ductility and strength. Bulk NS materials are usually synthesized by either a two-step approach involving the synthesis and consolidation of nanoparticles (e.g., via inert-gas condensation) [2,3] or nanocrystalline powders (e.g., via ball milling or cryomilling), [20] or a one-step approach such as severe plastic deformation (SPD). [21] In the case of NS materials prepared by the two-step approach, powder handling can yield extrinsic processing artifacts (such as porosity, incomplete bonding, impurities, and others). It is now well-established that these artifacts, when present, will cause premature failure under tensile stresses, sometimes even before the onset of yielding. [3] In a recent study, the material was consolidated in situ via an approach involving cryomilling followed by room-temperature milling. [22] In this case, the NS Cu prepared by this novel method was reported to have a uniform tensile elongation (strain before necking) of 14% and a high yield strength of 790 MPa. Despite these encouraging results, ...

Deformation-induced grain growth has been reported in nanocrystalline (nc) materials under indentation and severe cyclic loading, but not under any other deformation mode. This raises an issue on critical conditions for grain growth in nc materials. This study investigates deformation-induced grain growth in electrodeposited nc Ni during high-pressure torsion (HPT). Our results indicate that high stress and severe plastic deformation are required for inducing grain growth, and the upper limit of grain size is determined by the deformation mode and parameters. Also, texture evolution suggests that grain-boundary-mediated mechanisms played a significant role in accommodating HPT strain.

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This project is directed at advancing research and development in texture and anisotropy at Los Alamos. We are recognized as a national and international leader in texture and anisotropy research. This recognition is based on our understanding involving both quantitative texture analysis and the understanding and modeling of processes under which texture develops. In addition to these resources, we have available the full troika of texture measurement techniques, namely, x-ray, electron diffraction, and neutron diffraction. The goals of this project were (1) to increase the utilization of texture and anisotropy both within and without the Laboratory programmatic, basic, and industrial related efforts; (2) to seek to improve our texture measurement and modeling capabilities; and (3) to maintain our recognition as an international leader through basic research. These goals were accomplished through the formation of a coherent focus on texture directed through the CMS to coordinate texture efforts at the Laboratory as well as advancing the field in analysis, measurement and interpretation. The "texture focus" has essentially four functions: One, to manage the physical measurement systems; two, to coordinate human resources at the lab; three, to serve as a resource for both external and internal users; and four, to advance the field of texture analysis at all levels and keep it at the forefront.

We present the free surface response of 2, 5, and 8 m aluminum films to shocks generated from chirped ultrafast lasers. We find two distinct steps to the measured free surface velocity that indicate a separation of the faster elastic wave from the slower plastic wave. We resolve the separation of the two waves to times as short as 20 ps. We measured peak elastic free surface velocities as high as 1.4 km/s corresponding to elastic stresses of 12 GPa. The elastic waves rapidly decay with increasing sample thickness. The magnitude of both the elastic wave and the plastic wave and the temporal separation between them was strongly dependent on the incident laser drive energy.

The microstructure across a friction stir weld in aluminum alloy 2195 was analyzed to reveal the precipitation processes, grain evolution mechanisms, and crystallographic texture within that weld. The complex microhardness variations across the weld are explained by the observed precipitation sequence, in which the original precipitates coarsen and dissolve during welding, and are then replaced by different precipitates, which form during cooling. The grain development from the thermomechanically affected zone (TMAZ) into the weld nugget reveals that subgrains form within the TMAZ grains and develop increasing boundary misorientations through continuous dynamic recrystallization by subgrain rotation to eventually form the refined grains observed within the weld nugget. Within the weld nugget, a {112},110. texture is observed, corresponding to a high strain/high temperature shear strain component.

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