Search

In the present work, low cycle fatigue (LCF) behavior and fracture characteristic of Ti–6Al–4V-0.55Fe alloy with bimodal microstructure, consisted of equiaxed primary α (αp), lamellar α (αl) and β matrix, are systematically investigated at room temperature. Results indicate that Ti–6Al–4V-0.55Fe alloy mainly exhibits a continuous softening behavior both at high and low strain amplitudes, due to the interaction of back stress(σb) and friction stress(σf) mainly related to the plastic deformation heterogeneity and precipitates shearing, respectively. Compared with Ti–6Al–4V alloy, LCF life of Ti–6Al–4V-0.55Fe is similar at high strain amplitudes (Δεt/2 > 1.0%), while much higher at low strain amplitudes (Δεt/2

Microstructure, thermal conductivity and tensile properties of copper foils are significantly affected by few-layer graphene nanoplates (FLGNPs) as reinforcement embedded into Cu matrix. In the present study, FLGNPs and Cu2+ were co-deposited on the Ti substrate by direct current (DC) electrodeposition to obtain flexible Cu-FLGNPs composites. The texture orientation, phase structure, surface morphology, interface between FLGNPs and Cu matrix of the Cu-FLGNPs composites were characterized. The results show that thermal conductivity and tensile properties of the Cu-FLGNPs composites were increased firstly and then decreased in the process of electrodeposition. Thermal conductivity of the Cu-FLGNPs composites was enhanced from 311 ± 9 W m−1 K−1 characteristic for Cu up to 444 ± 13 W m−1 K−1 when the Gr content was 0.8 g L−1 and the graphene defect density was 6.30×1010 cm−2. Tensile strength of the Cu-0.8FLGNPs composites was 397 MPa, which was improved by 34% compared to the Cu matrix counterparts. Furthermore, the modified thermal model was proposed to evaluate the difference between experimental and theoretical thermal conductivity. The thermal conductivity mechanism was mainly ascribed to graphene defects, electron scattering, phonon scattering and interfacial thermal resistance. The electrodeposition of the Cu-FLGNPs composites provides a feasible route for heat dissipation of electronic and thermal management devices.

Measurement while drilling (MWD) has been widely used in petroleum drilling engineering because it can realize borehole trajectory monitoring and improve the drilling speed. However, the slurry erosion will deteriorate and shorten the life of MWD. A user-defined function (UDF) code was developed to calculate the particle properties (particle impact velocity, particle impact angle and particle impact number) and erosion depth to understand the erosion process. The results show that the Realizable κ-ε model can accurately predict the erosion profile and the erosion depth is consistent with the experiment results. Furthermore, high pressure will aggravate surface damage and expand the area of slurry erosion. It has been demonstrated that computational fluid dynamics (CFD) and experimental approach can be used to identify and explain the erosion mechanisms in different regions where the surface morphologies reveal four erosion patterns, namely, micro-cutting, cracks, pits and plastic deformation.

The role of the electrode in electric discharge machining (EDM) performance is crucial because it has an impact on the geometrical accuracy, machining efficiency and surface finish of the machined components. In the present work, a new technical approach combining equal channel angular pressing (ECAP) and deep cryogenic treatment (DCT) was put forward to manufacture copper electrodes for enhancing the machining characteristics of electric discharge machining (EDM). Effects of the ECAP, the ECAP + DCT on the EDM performances including the electrode wear rate (EWR), the workpiece corner sharpness (WCS), the surface roughness (Ra) and the surface characteristics of EDM workpieces have been investigated. The EWR after the ECAP and the ECAP + DCT was reduced to the minimum after two passes of ECAP. The EWR and WCS after the ECAP + DCT were less than that after the ECAP due to the higher hardness and electrical conductivity. The Ra of EDM workpieces using electrodes processed by the ECAP + DCT was slightly less than that after ECAP. An analogous Hall–Petch relation between the Ra of EDM workpieces and the grain size of electrodes was observed, indicating that ultrafine-grained electrodes processed by ECAP and the additional DCT would enhance the surface finish. The surface finish of EDM workpieces was discussed based on the features of the surface morphology.

The flexible nanotwinned graphene/copper (Gr/Cu) composite is successfully fabricated by pulse electrodeposition (PED). Microstructure, nanoindentation hardness, tensile properties, and thermal con...

A compound additive, gelatin (G) + sodium dodecyl sulfate (SDS), was firstly proposed to synthesize nanotwinned Cu with enhanced mechanical properties and electrical conductivity by direct current (DC) electrodeposition. The effect of compound additive in acid copper plating electrolyte on microstructure, nanoindentation hardness, tensile properties and electrical conductivity of electrodeposited copper was investigated. The optimum conditions of DC electrodeposition and deposition rate of electrodeposited copper were evaluated. The results show that the formation of nanotwins and the refinement of grains were enhanced after adding the 20 mg/L SDS + 15 mg/L G of compound additive, in return, which has a positive contribution to the enhanced mechanical properties and electrical conductivity. Tensile strength, hardness and the elongation to failure of electrodeposited Cu were 490 MPa, 1.79 GPa and 7.1%, respectively. The electrical conductivity was 97.4% IACS at room temperature. The enhancement mechanism of tensile properties and electrical conductivity was explained in view of high density of nanotwins.

The texture transition Cu {112}〈111〉 → S3 {123}〈634〉, untypical for the coarse-grained state, is discovered during the flat rolling of the ultrafine-grained (UFG) Cu-10 wt%Zn alloy. This fact is the evidence of a change in the deformation mechanisms which are related to the features of the UFG state produced by severe plastic deformation. Modeling in the framework of the viscoplastic self-consistent model enables establishing that such a transition is possible due to the suppression of the activity of the {110}〈110〉 slip systems and the {112}〈110〉 twinning systems with increasing reduction ratio. The main contribution is made by the octahedral slip via the {111}〈110〉 systems.

Cu-7%Al alloy subjected to equal channel angular pressing at cryogenic temperature with liquid nitrogen cooling (Cryo-ECAP)was treated by annealing. The microstructure and mechanical properties of Cu-7%Al alloy before and after annealing were investigated. It shows that a large number of annealing twins formed in Cu-7%Al alloy subjected to Cryo-ECAP. After 300∘C and 0.5 h annealing in Cu-7%Al alloy processed by Cryo-ECAP, tensile strength and uniform elongation was increased up to 644 MPa and 7.6% respectively. The enhanced mechanical properties of Cu-7%Al alloy after annealing is attributed to the high density nanoscale twins.

In the present work, new possibilities of the X-ray diffraction for investigations of the phase composition, size, shape and volume fraction of particles in ultrafine-grained ferritic/martensitic steel and the Cu-Cr-Zr alloy have been demonstrated. For the first time, the method of X-ray diffraction in the transmission mode was used to identify particles with a volume fraction of less than one percent in the ultrafine-grained materials studied. The small-angle X-ray scattering method was used to estimate the size and shape of dispersed particles. Specific features of the ultrafine-grained structure determined by the X-ray diffraction and transmission electron microscopy studies were used for estimation of dispersion hardening in the samples obtained by equal-channel angular pressing in comparison with the samples subjected to standard treatment.

The analysis of the strength characteristics and electrical conductivity of annealed Cu-1.0wt.%Cr-0.1wt%Zr alloy subjected to subsequent deformation under various conditions was carried out by analytical modeling methods. The contributions of the regions with nanotwins, as well as such defects of the crystal structure as vacancies, alloying atoms, dislocations, and particles of the secondary phase to the strength and electrical conductivity of the material were estimated.

The article studies an influence of temperature of severe plastic deformation (SPD) and post-deformation heat treatment on microstructure, mechanical properties and thermal stability of the Cu-0.5Cr-0.2Zr alloy. The results demonstrate that strength is considerably increased to 900 MPa by high pressure torsion (HPT) at room temperature. Subsequent ageing at 450 °С during 1 hour leads to a decay of solid solution and an allocation of dispersion particles that further incrises strength to 900 MPa, restores electrical conductivity to 70% IACS (International annealed copper standard) and enhances thermal stability of the alloy. When deformation temperature is increased to 300°С, strength is 690 MPa that is lower than in the case of deformation at room temperature that is related to reversion process at deformation. Additional a aging does not lead to an increase of strength characteristics.

In this paper we report a microstructure and strength properties investigations of a Cu-10 mass. % Zn alloy subjected to ECAP, with the aim of forming a UFG structure and enhancing the strength properties. The obtained results for this alloy having an average SFE value (35 mJ⋅m-2) are compared with the results obtained for pure UFG copper with a high SFE value equaled to 78 mJ⋅m-2. It is shown that the decrease in SFE value leads to more developed microstructure refinement, an increase in the density of dislocations and twins, which, in turn, provides an increase in strength characteristics.

An Al–3% B master alloy has been subjected to equal channel angular pressing (ECAP). The grain refining performance and fading resistance of an Al–3% B master alloy on a commercial purity Al (CPA) have been evaluated. The effect of the number of ECAP passes on the size and the distribution of the AlB2 particles, the grain size of CPA ingots with and without adding the Al–3% B master alloy subjected to ECAP have been investigated. The mean size of AlB2 particles was significantly reduced from ∼34 to ∼12 µm after four ECAP passes. Fine blocky AlB2 particles were uniformly distributed in the Al matrix. It has been revealed that when it was inoculated by the Al–B master alloy subjected to ECAP, the grain size of α-Al was decreased from ∼1200 to ∼180 µm after four ECAP passes, beyond that, the grain size tends to be saturated. It has been proved that grain refinement efficiency and fading resistance of the Al–3% B master alloy subjected to ECAP in CPA ingots was enhanced.

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.

Titanium alloys manufactured via additive manufacturing are suffering from coarse columnar grains due to the insufficient spontaneous nucleation rate during solidification. In this study, a newly designed Ti–2Fe-0.1B alloy with higher nucleating agent were introduced and manufactured by laser melting deposition method. The manufactured part is presenting a fully equiaxed grain morphology with 779 MPa on ultimate tensile strength. In order to reveal the mechanism of equiaxed grain formation and its influence on mechanical properties, a comprehensive study of microstructure evolution was carried out on Ti–2Fe-0.1B alloy manufactured via casting, forging and laser melting deposition. The results indicate that cooling speed are playing an important role on TiB morphology and Ti–2Fe-0.1B grain size simultaneously. The TiB formed from fast cooling speed are presenting a 3D quasi-network structure and improves the ultimate tensile strength of laser melting deposited part by 1.7 and 1.5 times when compared with casting and forging parts correspondingly. The study reveals that B addition is a sufficient method to control equiaxed grain formation in additive manufacturing of Ti–Fe alloy and promotes B addition as grain morphology controlling method in other additive manufactured titanium alloys in future.

The mechanisms of high-speed deformation of ultrafine-grained copper produced during severe plastic deformation by equal-channel angular pressing were analyzed using numerical modeling in comparison with those in the case of coarse-crystalline copper. The activity of annihilation processes during nonconservative motion and double cross slip of dislocations was estimated. Their effect on the macroscopic behavior of samples is shown.

The deformation mechanisms responsible for the strength and ductility of nanostructured Cu and Cu–Al alloys processed by high pressure torsion have been analyzed in frames of a model of elastic–plastic medium and using the available experimental data. The income of the Peierls strength, as well as solid solution hardening, dislocation hardening, twinning hardening, taking into account possible annihilation processes has been estimated. It was shown that in the Cu–5 at.% Al alloy annihilation processes contribute to the maintenance of deformation. The material is hardened by the accumulation of dislocations at the twin boundaries, postponing the moment of reaching the ultimate strength. In the Cu–16 at.% Al alloy processes of the annihilation are limited. As a result, the possibility of further deformation is limited and the degree of homogeneous deformation decreases in comparison with the case of the Cu–5 at.% Al alloy. Significantly increased concentration of deformation vacancies contributes to the destruction of the former alloy as well.

Cu Al alloys with different stacking fault energy (SFE) were processed by equal channel angular pressing and rolling (ECAP + R) at cryogenic temperature with liquid nitrogen cooling. The effect of SFE on microstructure, effective grain size, dislocation density and tensile properties has been investigated. With decreasing of SFE during cryogenic ECAP, shear bands were developed to be step-shaped by cutting through high density of deformation twins, effective grain size reduces and dislocation density increases. Subsequently imposed to cryorolling, the lamellar thickness of twins and grain size is further reduced. Tensile strength increases with a decrease of SFE, and further enhanced after the additional rolling. The improvement of strength in Cu Al alloys is attributed to the finer grains/twin thickness and the higher dislocations density. The maximum tensile strength of 871 MPa and uniform elongation of 4.3% in Cu 7%Al is simultaneously achieved.

The evolution of microstructure in the Cu-0.5%Cr-0.2%Zr alloy subjected to thermomechanical treatment has been studied by means of the x-ray analysis. The workpieces have been subjected to 1, 2, 4 and 8 passes of equal channel angular pressing, plain cold rolling and aging treatment. The results of the XRD investigations reflect the evolution of the lattice parameter, the size of coherently scattering domains, the elastic microdistortions and the dislocation density in Cu matrix. The observed changes in the microstructure are explained by the competition between the developing defects and precipitation of the Cr phase particles from the Cu matrix.

The differences of effective stress, effective strain, velocity field, and the load-time curves between the spider isothermal and non-isothermal forging processes are investigated by making full use of 3D FEA, and verified by the production experiment of spider forging. Effective stress is mainly concentrated on the pin, and becomes lower closer to the front of the pin. The maximum effective strain in the non-isothermal forging is lower than that in the isothermal. The great majority of strain in the non-isothermal forging process is 1.76, which is larger than the strain of 1.31 in the isothermal forging. The maximum load required in the isothermal forging is higher than that in the non-isothermal. The maximum experimental load and deformation temperature in the spider production are in good agreement with those in the non-isothermal FEA. The results indicate that the non-isothermal 3D FEA results can guide the design of the spider forging process.

In the present study, the unique bimodal grain size distribution microstructure with the ultrafine substrate and embedded macro grains was fabricated by a traditional hot-rolling process in a novel low-cost Ti-2Fe-0.1B titanium alloy, which possesses a good combination of strength (around 663 MPa) and ductility (around 30%) without any post heat treatment. Meanwhile, the mechanical behavior and corrosion resistance of hot-rolled Ti-2Fe-0.1B alloy after equal channel angular pressing (ECAP) deformation were studied. Results indicated that the average grain size decreased to 0.24 &mu, m after 4 passes ECAP deformation, which led to the enhancement of tensile strength to around 854 MPa and good ductility to around 15%. In addition, corrosion resistance was also improved after ECAP due to the rapid self-repairing and thicker passivation film. Our study revealed that the novel low-cost titanium alloy after hot-rolling and ECAP could be used instead of Ti-6Al-4V in some industrial applications due to similar mechanical behavior and better corrosion resistance.

The aim of this study was to investigate the corrosion resistance of ultrafine-grained (UFG) Ti-6Al-7Nb fabricated by equal channel angular pressing (ECAP) and coarse-grained (CG) Ti- 6Al- 7Nb. The microstructure of each specimen was investigated by the electron backscattered diffraction (EBSD) method. The corrosion behavior of each specimen was determined by electrochemical measurement in Ringer&rsquo, s solution. The surface corroded morphologies and oxide film formed on Ti-6Al-7Nb alloy after electrochemical measurement were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). EBSD investigation shows that the grain size of UFG Ti-6Al-7Nb decreased to ~0.4 &micro, m, accompanied by low angle grain boundaries (LAGBs) accounting for 39%. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicated that UFG Ti-6Al-7Nb alloy possessed a better corrosion resistance. The surface corroded morphologies revealed many small and shallow corrosion pits, which can be attributed to the good compactness of the oxide film and a rapid self- repairing ability of the UFG Ti-6Al-7Nb alloy.

Corrosion Resistance of ultrafine-grained (UFG) titanium alloys fabricated by equal channel angular pressing (ECAP) was investigated in this study. Electrochemical measurements of pure Ti and Ti-6Al-7Nb alloy were conducted in 3.5 wt.% NaCl and Ringer’s solution separately. Results indicated that both ultrafine-grained pure Ti and Ti-6Al-7Nb alloy had much lower corrosion current density than annealed coarse-grained counterparts in the specified corrosive environment.

The effect of equal-channel angular pressing (ECAP) on the strength and electrical conductivity of low-alloyed Cu-Cr-Zr alloys to identify conditions for the formation of states with high strength and electrical conductivity is considered. The increase in the content of alloying elements does not increase the strength of the alloys in the initial quenched state. After ECAP, their strength is increased by dislocations. It is shown that after ECAP of quenched samples, their specific resistances remain almost unchanged due to the increase in the length of the grain boundaries, the volume fraction of small particles of secondary phases and the segregation of alloying atoms from the matrix.

T-shaped equal channel angular pressing (T-shaped ECAP) is a novel process of severe plastic deformation (SPD). The maximum effective strain per pass in the T-shaped ECAP is larger than that in the ECAP. Deformation models of the T-shaped ECAP have been proposed by a designed grids deformation experiment considering the deformation dead zone (DDZ) formation or without it. Based on the deformation models, an upper bound approach has been used to analyse the T-shaped ECAP process. The effects of the plastic deformation zone (PDZ) angles and the friction factor on the relative pressing pressure and the DDZ are analysed. It is found that the relative pressing pressure increases with an increase of the angle and the friction factor m, however, the DDZ decreases. The upper bound solution for the T-shaped ECAP with the DDZ is more close to the experimental load than that without the DDZ. The results show that there is a good agreement between the theoretical value and the measured maximum load required for the T-shaped ECAP conducting.

The effect of stacking fault energy (SFE) on the mechanical properties of pure Cu and alloys of Cu-2.2%Al and Cu-4.5%Al subjected to severe plastic deformation (SPD) was investigated. SPD was performed by equal channel angular pressing (ECAP) at room and cryogenic temperatures. It is established that the increase in the weight concentration of Al in the Cu matrix (a reduction of SFE) and decreasing the ECAP temperature leads to an increase of the strength characteristics. The observed tendency is caused by increasing of the role of deformation twinning.

The results of studying the microstructure, mechanical and electrical properties of the UFG alloy Cu-0.5wt.% Cr, obtained by equal-channel angular pressing (ECAP), followed by cold rolling and subjected to aging, are presented. It was found that, as a result, the average size of the fragmented structure is 160 nm. The results showed that the tensile strength increases with increasing degree of deformation. The maximum strength value of 605 MPa was achieved after a combination of 8 ECAP passes followed by rolling by 95%, while ductility was reduced to 13%. The number of ECAP passes and subsequent rolling practically do not affect the electrical conductivity and is 34-39% of IACS.

In this paper, we use the scientometric approach based on the Web of Science Core Collection to analyze the data on publication activity in the area of nanostructured materials processed by severe plastic deformation (SPD) techniques on the following three main topics: ultrafine-grained materials, severe plastic deformation and bulk nanostructured materials. The results marked early 1990s as the starting period for first publications in question as well as their fast development. Pioneer works by Prof. Valiev and his laboratory at that time and their role in the growth of nanoSPD-related research were outlined.

Corrosion resistance of ultrafine-grained Ti processed by equal channel angular pressing with 3 passes was investigated. Results indicated that corrosion rate of ultrafine-grained Ti significantly reduced in comparison with coarse grain Ti. Furthermore, corrosion resistance of 3 passes ECAP sample had an obvious distinguish for different extraction planes; normal plane has shown a best corrosion resistance than transversal and extrusion plane, which could be attributed to higher fraction of low angle grain boundary.