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Abstract: Equal channel angular pressing results in ultrafine-grained (∼200–500nm) Ti with superior mechanical properties without harmful alloying elements, which benefits medical implants. To further improve the bioactivity of Ti surfaces, Ca/P-containing porous titania coatings were prepared on ultrafine-grained and coarse-grained Ti by micro-arc oxidation (MAO). The phase identification, composition, morphology and microstructure of the coatings and the thermal stability of ultrafine-grained Ti during MAO were investigated subsequently. The amounts of Ca, P and the Ca/P ratio of the coatings formed on ultrafine-grained Ti were greater than those on coarse-grained Ti. Nanocrystalline hydroxyapatite and α-Ca3(PO4)2 phases appeared in the MAO coating formed on ultrafine-grained Ti for 20min (E20). Incubated in a simulated body fluid, bone-like apatite was completely formed on the surface of E20 after 2days, thus evidencing preferable bioactivity. Compared with initial ultrafine-grained Ti, the microhardness of the E20 substrate was reduced by 8% to 2.9GPa, which is considerably more than that of coarse-grained Ti (∼1.5GPa). [Copyright &y& Elsevier]

The process of equichannel angular pressing (ECAP) is studied with the aim of fabricating large-size preforms with a diameter of 40 mm and a length of 160 mm from alloy 1421 to be used for forming sheets by subsequent warm rolling. Special features of the microstructure and optimum modes of superplasticity and mechanical properties of sheets with ultrafine-grain (UFG) structure are considered. [ABSTRACT FROM AUTHOR]

Nanostructured materials should present a good resistance to irradiation because the large volume fraction of grain boundaries can be an important sink for radiation-induced defects. The objective of the present study is to experimentally investigate the irradiation impact on the microstructure and mechanical properties in nanostructured materials. Nickel and Cu-0.5 Al2O3 specimens were synthesized by electro deposition (ED) and severe plastic deformation (SPD). Mean grain size of the unirradiated specimen is about 30nm for the ED Ni and about 115 nm for the SPI) Ni, 590 MeV proton irradiation and 840 kcV nickel ion irradiation were conducted at room temperature. Vickers hardness measurements and transmission electron microscope observation were performed to examine the impact of irradiation on nanocrystalline materials. It appears that the irradiation induced microstructure in Ni and in Cu-0.5Al2O3, which leads to hardening, consists exclusively of stacking fault tetrahedra. Their density appears much lower than in the case of coarser grained material. These results, experimentally showing the resistance of nanostructured material to radiation damage, are presented here. [ABSTRACT FROM AUTHOR]

In this work X-ray scattering techniques are used in full scale to characterize the microstructure of Al-2wt.%Cu alloy in order to state common and diverse features between artificial and dynamic ageing. Artificial ageing of the alloy is implemented via T6 regime, dynamic ageing occurs during high pressure torsion. X-ray phase analysis of diffraction patterns obtained in the transmission regime has for the first time identified and quantified the nanodisperse phases of precipitates in the both aged states. Lattice parameters, coherent scattering domains distribution over sizes, averaged dislocation density, fractions of edge and screw dislocations of Al phase after artificial and dynamic ageing are determined via the diffraction patterns obtained in the reflection regime. Small angle X-ray scattering (SAXS) technique has established quantitative characteristics of size, shape and distribution of precipitates in the mentioned states. In order to confirm the results of SAXS, transmission electron microscopy studies are performed on the same foils. Peculiarities of mechanisms of artificial and dynamic ageing in the studied alloy are discussed on the basis of the obtained data. [ABSTRACT FROM AUTHOR]

• 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]

The paper presents the results of investigations aimed at the processing ultrafine-grained (UFG) structures in commercial-purity Ti by equal-channel angular pressing (ECAP) at low temperatures (200, 300 °C). The most important processing factors influencing the formation of equiaxed UFG structures are studied. It is shown that the decrease of ECAP temperature and the increase of hydrostatic pressure in deformation zone contribute to the formation of finer grains. [Copyright &y& Elsevier]

Cryomilled nanocrystalline Al–7.5Mg (in wt.%) powders were consolidated by high pressure torsion (HPT). Consolidation resulted in elongated nanocrystalline grains of ∼30 nm width along the torsion direction and high microhardness values over 3.5 GPa at five rotations in torsion under applied pressures of 6 GPa. [Copyright &y& Elsevier]

Abstract The influence of additional low-temperature annealing on microstructure, strength and electrical сonductivity of Al-0.4Zr alloy has been studied. The alloy was preliminarily aged by long-term annealing at 375 °С for 60 h and processed by high pressure torsion (HPT), resulting in formation of ultrafine-grained (UFG) structure. Additional annealing of the alloy with a UFG structure at 230 °С for 1 h leads to substantial enhancement of strength (the yield stress by 40% and ultimate tensile strength by 20%). The hardening effect increases with increasing the annealing time to 3 h, and then it reduces smoothly. The strength enhancement due to annealing is accompanied by an increase in the electrical conductivity. The best combination of strength (the yield stress 149 MPa, the ultimate tensile strength 163 MPa) and electrical conductivity (55% IACS) was achieved after annealing for 3 h. The experimentally obtained changes of the yield stress and electrical resistivity at 77 К due to annealing are compared with the theoretical estimates. The analysis shows that the low-temperature annealing induces additional hardening mechanism in the UFG Al-0.4Zr, which is most likely associated with the rearrangement of high angle grain boundary structure. The obtained results suggest a new way to increase simultaneously strength and electrical conductivity of UFG Al-Zr alloys by an appropriate annealing. Highlights • Extremely high hardening by annealing was found for HPT-processed Al-0.4Zr alloy. • This effect assumes action of a new hardening mechanism in the annealed state. • Hardening by annealing is associated with rearrangement of HAGB structure. • The hardening is accompanied by an increase of electrical conductivity. • This opens a new approach to improve strength and conductivity simultaneously. [ABSTRACT FROM AUTHOR]

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]

An ultrafine-grained (UFG) austenite Cr-Ni stainless steel was produced by equal-channel angular pressing. The UFG samples were irradiated in a research nuclear reactor up to damaging doses of 12 and 15 dpa at 350 °C and 450 °C, respectively. The post-irradiation examination featured in this work covers microstructural and mechanical property changes at test temperatures of 20–650 °C. Microstructural studies showed that the concentration of Frank loops was considerably lower in the UFG steel compared to in the coarse-grained material. It was also found that irradiation resulted in precipitation of α-phase in triple junctions of the UFG steel. The post-irradiation examination of mechanical properties testified that the UFG steel exhibited lower irradiation hardening and higher strength compared to the coarse-grained material in the entire testing temperatures range, and improved ductility when tested at 500–650 °C. In summary, we testified that microstructure refinement of an austenite stainless steel down to UFG scale led to enhancement of its resistance to neutron irradiation at elevated temperatures. [ABSTRACT FROM AUTHOR]

Fabricating bulk coarse-grain Mg alloys into nanocrystallines (NCs) via severe plastic deformation along with remaining the thermal stability of nanostructures has been a challenging issue. Here we employed high-pressure torsion at room temperature to prepare nanocrystalline (NC) Mg-Gd-Y-Zr alloy with an average grain size of 80 nm. The appearance of NC structures was associated with stacking fault formation, due to the lowering of stacking fault energy by Gd and Y according to the density-functional theory (DFT) calculations. The NC Mg-Gd-Y-Zr alloy showed high thermal stability up to 250 °C, which is comparable with that of its coarse-grained and fine-grained counterpart. This high thermal stability against nanograin growth was caused by stable precipitation at grain boundaries. Therefore, alloying Mg with Gd and Y not only helped with formation of NCs, but also improved the thermal stability. [ABSTRACT FROM AUTHOR]

High-resolution electron backscatter diffraction (EBSD) was applied to examine grain refinement in commercial-purity titanium Grade 4 subjected to equal-channel angular pressing (ECAP) via the Conform technique. This approach enables the production of long-length billets and thus has the potential for commercial application. Microstructure evolution was found to be a relatively-complex process which included several stages. At relatively-low accumulated strains, microstructure changes were markedly influenced by mechanical twinning. However, the concomitant grain refinement suppressed this mechanism, and subsequent microstructure development was dictated by the evolution of deformation-induced boundaries which developed preferentially near the original grain boundaries. The final material produced after an effective strain of ~ 8.4 was characterized by a mean grain size of 0.3 µm, high-angle boundary fraction of 55 pct., a texture of moderate strength, and a yield strength of ~ 1050 MPa. Based on the detailed microstructural analysis, the contributions of various strengthening mechanisms were quantified. The rapid material strengthening during the early stages of ECAP was explained in the terms of a major increase in dislocation density and the extensive formation of the deformation-induced boundaries. With further increments in accumulated strain, however, the dislocation as well as grain-boundary density reached a saturation, thus reducing the hardening efficiency of ECAP at high strains. [ABSTRACT FROM AUTHOR]

This paper reports on a study of the relationship between microstructure, mechanical behavior and impact toughness of the UFG Grade 5 Ti alloy. The mechanical behavior and impact toughness of the Grade 5 Ti alloy in a coarse-grained state, and in an ultrafine-grained (UFG) state produced by equal-channel angular pressing (ECAP) with subsequent deformation-and-thermal treatments via extrusion and warm upsetting in isothermal conditions, were studied extensively. It is shown that a strong refinement of α -grains (less than 250 nm) in the alloy by ECAP and extrusion leads to high strength but with low values of the uniform elongation and lower impact toughness. It is demonstrated that, in order to increase the impact toughness of UFG Ti alloys, it is possible to use approaches realizing ductility enhancement associated with an increase of the strain hardening capacity. An enhancement in the impact toughness of the UFG alloy through an increase in the uniform tensile elongation of the sample is achieved by the preservation of the ultrafine size of α -grains (about 800 nm) with predominantly high-angle boundaries and a decrease in the dislocation density due to recovery and dynamic recrystallization during warm upsetting. [ABSTRACT FROM AUTHOR]

Electron backscatter diffraction was applied to examine the microstructure developed in commercial-purity titanium subjected to equal channel angular pressing at 200 °C to a true strain of 8.4. The microstructure was characterized by a mean grain size of 0.4 μm and fraction of high-angle boundaries of 55%. However, it also contained a significant fraction of relatively coarse (>1 μm) remnants of original grains. A microstructure-properties analysis indicated that strengthening effect of ECAP was essentially contributed by substructure. [ABSTRACT FROM AUTHOR]

The influence of microstructure evolution on microhardness and electrical resistivity of ultrafine grained (UFG) commercial purity Al under annealing at different temperatures within a range of 363–673 K was studied. The initially coarse grained Al was processed by high pressure torsion (HPT) technique for the formation of UFG structure. The microstructure was characterized by electron backscattering diffraction and X-Ray diffraction. It was shown that annealing of UFG Al at temperatures within a range of 363–473 K leads to simultaneous increase of microhardness (by 6–13%) and electrical conductivity (by 4–8% at 300 K). The correlation between microstructural features and the resulting properties were analyzed. The average width s of potential barriers at grain boundaries (GBs) in HPT-processed Al was estimated in the frame of a tunnel model. The obtained large value of s compared with the GB crystallographic width is associated with elastically distorted lattice near GBs. The obtained results suggest a new way to increase simultaneously strength and electrical conductivity of UFG Al alloys by an appropriate annealing. [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]

The changes due to pulsed plasma flow irradiation on the near-surface microstructure and mechanical properties of the high-chromium, ferritic–martensitic steel EK-181 (Fe16Cr12W2VTaB) have been quantified. Irradiation of EK-181 in this manner produces a microstructural gradient near the material surface, with a two dimensional nanostructured cellular surface. The microstructure and mechanical properties of the modified layer are independent of the initial microstructure and phase composition, and are strongly defined solely by parameters of the plasma flow. High thermal stability of the pulsed plasma-modified layer was explicitly demonstrated. [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]

• Equiaxed grains of Ti–2Fe–0.1B alloy transformed into lamellar structure after hydrogenation. • 0.3 wt% hydrogen addition led to the increase of β phase from 4.95% to 30.1%. • The addition of 0.3% H enhanced the yield strength of Ti-2Fe-0.1B alloy. • Flow stress of hydrogenated Ti-2Fe-0.1B alloy decreased extremely during hot compression. [Display omitted] A low-cost Ti-2Fe-0.1B alloy with high performance was manufactured and hydrogenated in this study. The effect of 0.3 wt% hydrogen addition on microstructure evolution, compression deformation behavior at room and high temperature of Ti–2Fe–0.1B alloy has been investigated. Results indicated that lamellar α L structure along with martensite α′ are formed after hydrogenation compared with initial equiaxed grains, and the fraction of β phase increased from 4.95% to 30.1%. Obvious phase transformation α eq →α H + β H , β→β H during hydrogenation and β H →α + δ, α H →α + δ during subsequent cooling occurred. The hydrogenated Ti-2Fe-0.1B alloy is characterized by hardening effect during compression deformation at room temperature along with the loss of ductility due to the solid solution strengthening by hydrogen atoms and presence of hydride δ. However, peak flow stress of hydrogenated Ti-2Fe-0.1B alloy decreased from 49 MPa to 29 MPa extremely during compression deformation at 973 K, which can be attributed to the high volume of β phase induced by hydrogenation, as well as the promotion of dynamic recovery and dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Abstract: In the current study the mechanical properties of ultra-fine grained low carbon steel processed by conventional equal channel angular pressing and a continuous equal channel angular pressing-Conform process were investigated. Both monotonic and cyclic properties were determined for the steel in either condition and found to be very similar. Microstructural analyses employing electron backscatter diffraction were used for comparison of the low carbon steels processed by either technique. Both steels feature very similar grain sizes and misorientation angle distributions. With respect to fatigue life the low carbon steel investigated shows properties similar to ultra-fine grained interstitial-free steel processed by conventional equal channel angular pressing, and thus, the general fatigue behavior can be addressed following the same routines as proposed for interstitial-free steel. In conclusion, the continuously processed material exhibits very promising properties, and thus, equal channel angular pressing-Conform is a promising tool for production of ultra-fine grained steels in a large quantity. [Copyright &y& Elsevier]

Abstract: Microstructure and mechanical properties of copper subjected to 1–10 ECAP passes via route Bc were compared with those for further cold rolled specimens. Microstructure was studied by means of TEM and EBSD analysis in three orthogonal sections. Rolling caused transformation of reasonably equiaxed structure after ECAP into lamellar one due to geometrical effect of deformation, but almost no additional grain refinement occurred during rolling. Significantly higher extent of HABs (about 20% irrespectively to passes number) was found after rolling. This was associated with more pronounced dynamic restoration process during rolling. Mechanical properties were estimated by tension testing at room temperature. Yield strength increased by ∼100MPa after rolling due to finer boundary spacing according to Hall–Petch relationship. [Copyright &y& Elsevier]

Abstract: Fully dense, nanocrystalline tantalum (average grain size as small as ∼40nm) has been processed for the first time by high-pressure torsion. High-resolution transmission electron microscopy reveals non-equilibrium grain boundaries and grains decorated with high-density dislocations. Microhardness measurements and instrumented nanoindentation experiments indicate that the mechanical property is quite uniform except for the central area of the disks. Nanoindentation experiments at different strain rates suggest that the strain rate sensitivity of nanocrystalline tantalum is increased compared to the coarse- and ultrafine-grained counterparts and is accompanied by an activation energy of the order of a few ∼b 3 (b is the magnitude of the dislocation Burgers vector), implying a shift in the plastic deformation mechanism from the screw dislocation dominated regime. We thus infer the plastic deformation mechanisms of nanocrystalline body-centered cubic (bcc) and face-centered cubic metals converge. To examine the stress–strain behavior, we have used microcompression to measure the compressive stress–strain curves on microscale pillars fabricated by focused ion beam technique. Yield strength as high as 1.6GPa has been observed. High-strain rate behavior has been investigated using a miniature Kolsky bar system. We have found that at high-strain rates the nanocrystalline tantalum specimens exhibit adiabatic shear banding, a dynamic plastic deformation mode common to many ultrafine-grained and all nanocrystalline bcc metals. [Copyright &y& Elsevier]

Abstract: The microstructure and the mechanical properties of ultrafine grained Pd and Pd–x% Ag (x =10, 20, 40) alloys processed by high pressure torsion (HPT) were thoroughly investigated using transmission and high resolution electron microscopy, XRD analysis and tensile tests. The increased Ag content resulted in decrease of the stacking fault energy (γ SF), which made it possible to produce by means of HPT different ultrafine-grained structures in the alloys and to study their superior strength and ductility. The nature of such unique mechanical behaviour is discussed on the basis of analysis of strain hardening mechanisms and effect of stacking fault energy. [Copyright &y& Elsevier]

Abstract: Microstructure evolution in severely deformed Cu has been investigated using high-energy synchrotron light during in situ high-pressure torsion (HPT) at room temperature. Relative changes in broadening of Bragg peaks and crystal lattice expansion were studied in the loading–unloading regime of torsion straining. Experimental results revealed fast relaxation (on the order of hundred of seconds) that occurred due to annihilation of HPT-induced crystal lattice defects, which were generated directly during deformation. The kinetics of relaxation is probably diffusion-controlled; therefore, the enhanced diffusivity can be explained by extremely high excess vacancy concentration, which is usually achieved at thermal equilibrium near the melting point. [Copyright &y& Elsevier]

Abstract: It was shown that introducing an ultrafine-grained (UFG) microstructure in pure metals as well as some alloys leads to strongly enhanced fatigue properties. The cyclic deformation behavior of UFG Ti-6Al-4V ELI (extra low interstitials) alloy is studied by both strain and stress controlled fatigue tests using plastic strain amplitudes between 3×10−4 and 5×10−3 and stress amplitudes ranging from 550 to 670MPa. The UFG microstructures were obtained by equal channel angular pressing (ECAP) with different number of passes followed by a subsequent thermomechanical treatment (TMT). When compared to the conventional grain (CG) size counterpart, the UFG alloy exhibited a pronounced enhancement in the fatigue life in the S–N (Wöhler) diagram. It was also shown that additional UFG processing prior to TMT did not result in any further improvement of the fatigue resistance. Furthermore, microstructural investigations revealed a high cyclic stability of the UFG microstructure. [Copyright &y& Elsevier]

Abstract: The influence of high-pressure torsion (HPT) at various temperatures on microstructure and mechanical properties of commercially pure (CP) titanium (Grade 4) has been studied using transmission electron microscopy and tensile tests. The temperature range of 70–450°C for isothermal HPT processing has been used to fabricate nanocrystalline samples with diameter 20mm under a pressure of 6GPa. Using the new installation, we demonstrated that the ultimate tensile strength of CP Ti (Grade 4) after HPT processing achieves 1600MPa as a result of significant grain refinement. At the same time, ductility of the HPT samples has been affected strongly by processing and annealing temperature. [Copyright &y& Elsevier]

Abstract: Fully dense nanocrystalline tungsten (nc-W) with extremely high strength (∼3.0GPa under quasi-static compression and ∼4.0GPa under dynamic compression) has been obtained by high-pressure torsion (HPT) at low temperature (500°C). The nanocrystalline microstructure is revealed by transmission electron microscopy (TEM). The grain boundaries (GBs) are mostly of the large-angle type. High-resolution TEM (lattice images) suggests that the GBs are clean and well defined (atomically sharp). GBs are non-equilibrium and of a high-energy nature. Edge dislocations are present within the grains. The authors hypothesize that these edge dislocations, combined with a depleted impurity concentrations along pre-existing GBs, contribute to enhance the ductility of nc-W. Under dynamic compression, the specimens exhibit localized shearing followed by cracking and subsequent failure, similar to their ultrafine-grain (UFG) counterparts processed by equal-channel angular pressing plus cold rolling, and to many other body-centered cubic metals with UFG/nanocrystalline microstructures. The shear band width in the HPT-processed nc-W is much smaller (shear band width <5μm) than that observed in the UFG counterparts (shear band width ∼40μm). [Copyright &y& Elsevier]

Abstract: Microstructure development during severe plastic deformation by simple shear is modeled using a disclination model for substructure formation incorporated into the viscoplastic self-consistent (VPSC) polycrystal model. The strain incompatibilities between a homogeneous effective medium and a grain calculated by the VPSC model are assumed to result in an accumulation of disclinations at junctions of the grain. These disclinations are then relaxed by the growth of low-angle dislocation boundaries from the junctions. These boundaries split the grain into smaller, misoriented volumes which with further deformation can lead to its subdivision into new grains. The evolution of misorientation angles between the newly formed grains and the parent with applied straining agrees reasonably well with experimental misorientation angle distributions for geometrically necessary boundaries. Accounting for subgrain boundaries and grain subdivision results in textures after large strains that are more diffuse and lower in intensity than those predicted using standard VPSC modeling. [Copyright &y& Elsevier]

Abstract: We have systematically investigated the quasi-static and dynamic mechanical behavior (especially dynamic failure) of ultra-fine grained (UFG) tungsten (W) under uniaxial compression. The starting material is of commercial purity and large grain size. We utilized severe plastic deformation to achieve the ultrafine microstructure characterized by grains and subgrains with sizes of ∼500nm, as identified by transmission electron microscopy. Results of quasi-static compression show that the UFG W behaves in an elastic–nearly perfect plastic manner (i.e., vanishing strain hardening), with its flow stress approaching 2 GPa, close to twice that of conventional coarse grain W. Post-mortem examinations of the quasi-statically loaded samples show no evidence of cracking, in sharp contrast to the behavior of conventional W (where axial cracking is usually observed). Under uniaxial dynamic compression (strain rate ∼103 s−1), the true stress–true strain curves of the UFG W exhibit significant flow softening, and the peak stress is ∼3GPa. Furthermore, the strain rate sensitivity of the UFG W is reduced to half the value of the conventional W. Both in situ high-speed photography and post-mortem examinations reveal shear localization and as a consequence, cracking of the UFG W under dynamic uniaxial compression. These observations are consistent with recent observations on other body-centered cubic metals with nanocrystalline or ultrafine microstructures. The experimental results are discussed using existing models for adiabatic shear localization in metals. [Copyright &y& Elsevier]

The paper reports on the formation of ultrafine-grained structure in the Ti–6Al–4V alloy by equal-channel angular pressing (ECAP). ECAP processing with various regimes on die-sets with angles of channels intersection equal to 135° and 120° has been studied. Special attention is paid to the features of the processed microstructures and properties of the ECAP samples. It is shown that low-temperature deformation applied after ECAP contributes to additional strengthening of the alloy preserving sufficient ductility. [Copyright &y& Elsevier]

Two kinds of shear bands (SBs) which are persistent slip bands (PSB)-like SBs and step-like SBs were found in cyclically deformed ultrafine grained copper processed by ECAP. The SBs and adjacent microstructures were investigated using electron channeling contrast in scanning electron microscope (SEM-ECC). The possible formation mechanisms of SBs are discussed based on the cooperative grain boundary sliding. [Copyright &y& Elsevier]

Abstract: Ultrafine-grained (UFG) Ti rods were produced via cold rolling UFG and coarse-grained (CG) Ti stocks. The initial UFG stock was produced via equal channel angular pressing. It was found that the initial UFG structure had beneficial influence on the mechanical properties of the cold-rolled Ti rods. Compared with Ti rods with initial CG microstructure, the Ti rods with the initial UFG microstructure have both higher strength and higher ductility after being cold rolled to varying strains. Transmission electron microscopy revealed that the Ti rods with the initial UFG microstructure had finer, more homogeneous microstructures after cold rolling. This study demonstrates the merit of UFG Ti processed by ECAP for further shaping and forming into structural components with superior mechanical properties. [Copyright &y& Elsevier]

Microstructures and mechanical properties of equal-channel angular pressing (ECAP) processed and naturally aged ultrafine grained (UFG) and coarse grained (CG) 7075 Al alloys as well as their evolutions during annealing were investigated. After the same natural aging, the tensile yield strength, ultimate strength, and microhardness of the UFG samples were 103%, 35%, and 48% higher, respectively, than those of the CG samples, because of higher densities of Guinier–Preston (G–P) zones and dislocations in the UFG sample. Upon annealing, the microhardness of the UFG sample decreased gradually, while a hardening peak appeared for the CG sample. The peak was caused by the precipitation hardening of the metastable η′ phase. For the UFG sample, the precipitation hardening was overcompensated by the significant decrease of microstrain (dislocation density) upon annealing, resulting in a lack of precipitation hardening peak. Differential scanning calorimetry indicates that the ECAP process only accelerated the phase precipitations, but did not change the sequence of phase precipitation. This study shows that severe plastic deformation has the potential to significantly improve the mechanical properties of age-hardening Al alloys. [Copyright &y& Elsevier]

Cyclic deformation was performed on ultrafine grained copper processed by ECAP. Shear bands (SBs) and adjacent microstructures were investigated using electron channeling contrast in scanning electron microscope. The possible formation mechanism of SB was discussed based on the characteristic distribution of defects introduced by ECAP. [Copyright &y& Elsevier]

Abstract: Evolution of the microstructure and mechanical properties of Al–30wt.% Zn alloy after the severe plastic deformation (SPD) by the high-pressure torsion has been investigated in detail in dependence on the increasing deformation degree. SPD leads to the gradual grain refinement and decomposition of the Al-based supersaturated solid solution. Measurements of the microhardness reveal a successive softening of the alloy with the increased deformation degree. [Copyright &y& Elsevier]

Abstract: A coarse-grained (CG) Al6061 alloy after solution treatment is subjected to high pressure torsion at room temperature resulting in the formation of a homogeneous ultra-fine grained (UFG) microstructure with average grain size of 170nm. Tensile tests are performed at room and liquid nitrogen temperatures for both CG and UFG conditions. Analysis of the surface relief of the tested specimens is performed. The effect of microstructure on the mechanical properties and on the deformation behavior of the material is discussed. [Copyright &y& Elsevier]

Abstract: In this study the cyclic deformation behavior and fatigue lives of Ti–6Al–4V ELI (extra low interstitials) alloy with conventional grain sized and ultrafine-grained (UFG) microstructure are investigated. The UFG condition was obtained by a combination of equal channel angular pressing followed by thermomechanical treatment. Fatigue experiments were carried out under strain as well as under stress control using plastic strain amplitudes ranging from 3×10−4 to 5×10−3 and stress amplitudes ranging from 550 to 670MPa, respectively. Based on the results obtained, it can be concluded that the UFG microstructure results in a significant enhancement of the fatigue properties of the alloy. [Copyright &y& Elsevier]

Abstract: A slightly Ni-rich nano-NiTi alloy, deformed by high-pressure torsion (HPT) was investigated. By HPT, almost complete amorphization of initial B2 NiTi is obtained. Crystallization and microstructure evolution during isothermal treatment were investigated by differential scanning calorimetry (DSC) and transmission electron microscopy. The DSC signals observed during continuous heating experiments indicate an unusually large separation between the crystallization and the growth stages. A detailed analysis of the evolution of the enthalpy release upon annealing reveals reproducibly non-monotonous trends with annealing time that cannot be explained solely by growth of crystalline volume fractions. The size of nanocrystals increases dramatically after annealing for 5h. The effective activation enthalpies for stress relaxation (along with crystallization) and grain growth were estimated at 115 and 289kJ/mol, respectively. The results are discussed with respect to the intricate interdependencies between synthesis and thermal processing pathways and the evolution of the nanoscale microstructure. [Copyright &y& Elsevier]