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The high strength and increased electrical conductivity of the Al alloys are highly desirable for their applications in power transmission lines. However, high strength and high electrical conductivity are mutually exclusive in metallic materials. A novel nanostructuring strategy is reported that achieves Al–Mg–Si alloys with superior tensile strength and enhanced electrical conductivity. The new strategy is based on a combination of grain refinement down to ultra-fine scale with accelerated formation of nanosized precipitates during severe plastic deformation. [ABSTRACT FROM AUTHOR]

Cast Co-5.6 wt% Cu and Co-13.6 wt% Cu alloys were subjected to severe plastic deformation (SPD) by high-pressure torsion (HPT). The HPT treatment drastically decreases the size of the Co grains (from 20 µm to 100 nm) and the Cu precipitates (from 2 µm to 10 nm). As a result, the coercivity Hc of both the alloys radically increases. The saturation magnetization, Ms, remains almost unchanged. Thus, SPD of the bulk samples opens the way for drastic increase in the coercivity for the Co-based alloys. [ABSTRACT FROM AUTHOR]

Abstract: The discoveries made in Prof. A.K. Mukherjee''s laboratory in 1996–2001 have revealed that nanostructured metals and alloys can demonstrate extraordinary superplasticity at low temperatures and/or high strain rates. This work presents the new results on superplasticity in several nanostructured Al and Ti alloys focusing on microstructure evolution and strain hardening, as well as the challenges of their application. Grain refinement in these alloys was accomplished using severe plastic deformation techniques, and subsequent superplastic deformation allowed not only to produce their efficient forming, but also to improve the ultrafine-grained structure and to obtain enhanced mechanical properties of the produced articles. The results demonstrate the possibilities of new applications of superplastic forming using nanostructured materials. [Copyright &y& Elsevier]

• Two-phase TiNiCuNb alloy was subjected to HPT process. • Nanocrystalline bands alternating with amorphous phase after HPT. • Nanoscale debris are embedded into amorphous phase. (Ti 54 Ni 34 Cu 12) 90 Nb 10 alloy with initial two-phase structure of B19 martensite and β-Nb phase was subjected to high-pressure torsion (HPT) process at room temperature. HPT leads to the formation of nanocrystalline bands of β-Nb phase alternating with amorphous matrix. Nanocrystalline debris of B2 phase was found to be embedded into the amorphous matrix. Refinement of β-Nb phase upon HPT is much greater compared to that for pure Nb alloy. [ABSTRACT FROM AUTHOR]

The influence of grain boundary segregation on the strength of a nanostructured austenitic stainless steel was investigated. The steel was nanostructured by severe plastic deformation at two different temperatures to form ultrafine-grained states different by microstructure parameters. It is shown that despite the difference in grain size both nanostructured steels demonstrated the same level of strength. For the first time it is directly observed that severe plastic deformation at elevated temperature leads to formation of Mo–Cr–Si rich grain boundary segregations in the steel. Considering different contributions to the material strengthening, we demonstrate that grain boundary segregations can lead to significant enhancement of the yield stress. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, much progress has been made in the studies of nanostructured Al alloys for advanced structural and functional use associated both with the development of novel routes for the fabrication of bulk nanostructured materials using severe plastic deformation (SPD) techniques and with investigation of fundamental mechanisms leading to improved properties. This review paper discusses new concepts and principles in application of SPD processing to fabricate bulk nanostructured Al alloys with advanced properties. Special emphasis is placed on the relationship between microstructural features, mechanical, chemical, and physical properties, as well as the innovation potential of the SPD-produced nanostructured Al alloys. [Copyright &y& Elsevier]

Abstract: The generated results on superplastic flow (SPF) in materials produced by severe plastic deformation (SePD) have been analyzed. Formation of sliding surfaces with subsequent cooperative grain boundary sliding (CGBS) has been demonstrated to be a main deformation mechanism of superplasticity under conditions of microstructural stability. A substantial role of dislocation glide in accommodation processes is shown. When grain growth is observed during deformation, continuous grain boundary migration prevents formation of slide surfaces and CGBS is restrained. In this case, deformation of the material is more likely to occur by dislocation or diffusion creep than true SPF despite relatively large strains being reached. [Copyright &y& Elsevier]

Model Fe-Cr alloys with and without W were nanostructured by severe plastic deformation at 350˚C. Transmission electron microscopy observations of the microstructure indicate that the addition of 1 wt% of W led to a reduction of the mean grain size from 129 to 110 nm. Atom probe analyses show that only Cr and Si segregate at grain boundaries during deformation while W remains homogeneously distributed. This solid solution leads to higher mechanical strength and plasticity as compared to Fe-Cr. The origin of the beneficial effect of W on the mechanical performance is discussed. [ABSTRACT FROM AUTHOR]

The initial grain size of TWIP steel can affect the deformation mechanism during the HPT processes and the mechanical properties of severely deformed TWIP steels, contrary to the common belief that responses to the severe plastic deformation of metallic materials are not affected by initial grain size. [ABSTRACT FROM AUTHOR]

We report on the changes in microstructure and phase composition in a high-Mn steel due to severe plastic deformation realized via high pressure torsion at different temperatures. Severe straining conducted at 20 °C and 300 °C allowed producing nanostructural states with a mean grain size less than 100 nm. Besides, straining at room temperature leaded to formation of strain-induced ε -martensite while at 300 °C fully austenite state was produced. Despite the revealed differences both states demonstrated similar, notably increased level of hardness up to ∼580 Hv. [ABSTRACT FROM AUTHOR]

This work focuses on the effect of high pressure torsion (HPT) on the thermostability, microstructure, mechanical properties and electrical conductivity of an Al–8.5 wt.% RE (RE stands for rare earth Ce and La in the present case) alloy with respect to its potential application in electrical engineering. HPT processing leads to the formation of a very homogeneous ultra-fine grained microstructure resulting from the fragmentation of RE-rich intermetallic particles down to the nanoscale. Deformation induced supersaturated solid solution of RE atoms in the Al matrix is demonstrated for the first time. The HPT processed material shows an extraordinary high mechanical strength attributed to the high volume fraction of nanoscaled intermetallic particles and the ultrafine grained (UFG) microstructure. The various strengthening contributions were analyzed, and it was shown that the increase of strength during short time annealing could be attributed to the clustering of RE atoms in solid solution. The HPT processing induces a significant reduction of the electrical conductivity, but it was partly restored by annealing thanks to the concomitant clustering of RE atoms, reduction of dislocation density and grain growth. The potential applications of UFG Al–RE alloys in electrical engineering are finally discussed. [ABSTRACT FROM AUTHOR]

In this work, X-ray scattering methods were applied for a quantitative characterization of the microstructure of an aluminum alloy of the Al–Mg–Si system during dynamic aging realized through the high pressure torsion technique. A qualitative and quantitative phase analysis of the alloy was performed, together with Al alloy lattice parameter determination. From the reflections broadening the effective size of the coherent scattering domains and the lattice microstrain were determined in the framework of the Halder–Wagner approach. Using the method of small-angle X-ray scattering, the quantitative characteristics of the size, shape and spatial distribution of the secondary phase particles formed in the Al alloy during dynamic aging were established. In order to validate the obtained results, the method of small-angle X-ray scattering was preliminarily tested on similar samples after artificial aging and compared with the results from small-angle neutron diffraction widely known in literature. [ABSTRACT FROM AUTHOR]

• Ti 29.7 Ni 50.3 Hf 20 alloy subjected to HPT-process at RT and 300 °C. • Amorphous phase and nano-crystalline debris was found after HPT at RT. • Two types of structure were found after HPT at 300 °C. Ni 50.3 Ti 29.7 Hf 20 alloy was subjected to high-pressure torsion (HPT) process at room temperature (RT) and 300 °C. The mix of amorphous phase and nanocrystalline debris was found by TEM observation in sample processed at RT. Two types of structure were clearly distinguished after HPT at 300 °C: the first one is martensite-like plates oriented in single direction; the second is nanocrystalline structure with narrow amorphous bands. The fraction of amorphous phase is significantly larger after RT deformation. [ABSTRACT FROM AUTHOR]

Chemical short-range ordering is an important structural feature that would significantly affect materials properties, including mechanical properties. Chemical short-range ordering has been discovered in many alloy systems and usually forms at high temperatures during the materials synthesis or thermal annealing processes. Here we report chemical short-range ordering in an ultrafine-grained supersaturated Al-Zn alloy introduced by severe plastic deformation (strain >1) at room temperature. The chemical short-range ordering results in an ordered L1 0 -AlZn structure with the dimensions of 1–3 nm. It is believed that vacancies introduced by severe plastic deformation play an important role in the formation of the chemical short-range ordering at room temperature. [Display omitted] [ABSTRACT FROM AUTHOR]

We report a significant grain size effect on the phase transformation in a Ti–36Nb–2.2Ta–3.7Zr–0.3O alloy during severe plastic deformation. For grain sizes larger than the submicrometer range, the body-centered cubic β phase transformed to hexagonal ω phase when deformed by high-pressure torsion under a relatively low pressure of 3GPa and at room temperature. However, a reverse ω to β transformation was observed under the same deformation conditions when the grain sizes were less than 100nm. [Copyright &y& Elsevier]

Abstract: The high-cycle fatigue behavior of smooth and notched samples of ultrafine-grained titanium prepared by severe plastic deformation is compared with the corresponding properties of conventional titanium. It is shown that the combination of high strength and enhanced ductility of ultrafine-grained titanium lead to an increase of the fatigue endurance limit. Using a combination of equal-channel angular pressing and subsequent thermal and mechanical treatment, it was possible to increase the fatigue endurance limit of commercial-purity titanium by a factor of 1.5. Furthermore, it is shown that post-deformation annealing can additionally enhance the ductility of the ultrafine-grained Ti and lower fatigue-notch sensitivity particularly in comparison with Ti-6Al-4V. [Copyright &y& Elsevier]

• Physical-vapor deposited (PVD) coating was applied to Ultra-fine grained (UFG) Ti alloy. • PVD coating improves protective properties and provides higher endurance of UFG Ti alloy. • PVD coating on UFG Ti alloy has large increase in adhesive strength vs. when on coarse-grained alloy. • PVD-coated UFG Ti alloy exhibits high erosion resistance under gas-abrasive wear. The paper presents the results of a study of the service properties of an ion-plasma protective coating deposited on a titanium substrate with an ultrafine-grained structure in the process of Physical vapor deposition (PVD). Data on the microhardness, adhesion strength, and erosion resistance of the ion-plasma coating on the Ti-6%Al-4%V alloy with the initial Coarse-grained (CG) structure and Ultrafine-grained (UFG) state produced by Severe plastic deformation (SPD) are presented. Data were also obtained on the long-term strength of cylindrical specimens in the UFG state with and without coating at the operating temperatures of this alloy. A significant increase in the service properties of the coating on the titanium alloy with an UFG structure was established in comparison with the properties of this coating on the original coarse-grained alloy. The physical nature of the increase in the properties of the coating on the UFG alloy is discussed and a hypothesis about the influence of the UFG state of the substrate on the fine microstructure and properties of the protective coating is considered. [ABSTRACT FROM AUTHOR]

Ti–6Al–7Nb containing harmless for tissues niobium can be a good choice replacing Ti–6Al–4V for orthopedic implants application. Formation of ultrafine-grained (UFG) structure in metals and alloys by severe plastic deformation (SPD) techniques allows for achieving unique mechanical properties. Using equal channel angular pressing (ECAP) UFG structure in Ti–6Al–7Nb alloy with an average size of grains/subgrains of 200 nm was obtained. This UFG Ti–6Al–7Nb alloy has high mechanical (ultimate tensile strength 1470 MPa) and fatigue properties, suitable for practical application. Additionally, surface modifications of titanium alloys aim induce specific responses on osteoblastic cells after implantation. Chemical surface treatments are simple methods to obtain a bioactive for apatite precipitation surface. Phosphoric acid etching combined or not with alkaline treatment presented bioactivity after seven days soaked in simulated body fluid (SBF) solution. [ABSTRACT FROM AUTHOR]