Search

We propose pathways to produce high-strength thermal resistant Mg-doped Al–Zr-based conductors to be manufactured in the form of ultrafine-grained wires via deliberate thermomechanical treatment, including aging, continuous equal-channel angular pressing and cold drawing. Al–0.97Mg–0.35Zr and Al–1.17Mg–0.34Zr (wt.%) alloys were chosen as objects for investigation to reveal the effect of Mg on the alloys' properties in the processed states. Prior to deformation, the initial rods of the studied alloys were aged at 400 °C for 72 h to attain precipitation of nano-sized particles of the metastable phase Al3Zr (L12) in the aluminum matrix. The following refinement of microstructure in the aged alloys by severe straining followed by cold drawing allows achieving a promising combination of ultimate tensile strength over 320 MPa, plasticity with elongation to failure over 2% and electrical conductivity about 50% IACS. We show that the produced wires exhibit thermal resistance similar to that of the commercial high-strength heat-resistant aluminum alloy (KTAL) type AT2 wire, but with a markedly superior strength. The Mg concentrations and parameters of thermal and mechanical processing that maintain a reasonable trade-off between high strength and acceptable electrical conductivity are discussed on the basis of the presented and earlier reported data to produce high-performance heat-resistant UFG Al–Mg–Zr wires. [ABSTRACT FROM AUTHOR]

This work investigates the influence of parameters of initial ultrafine-grained (UFG) structure in commercially pure (CP) Al on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects. UFG structures were formed via processing CP Al by various methods of severe plastic deformation (high pressure torsion (HPT), equal channel angular pressing (ECAP) and combination of ECAP and cold rolling (CR)). AIH and DIS effects are observed in all the studied UFG structures. However, HPT Al demonstrates large increase of strength due to annealing and drastic gain of ductility after subsequent additional deformation whereas in ECAP Al and ECAP þ CR Al both effects are much less pronounced. Microstructure characterization by X-ray diffraction (XRD) analysis, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) was performed for HPT Al and ECAP þ CR Al in the three studied states: before and after annealing and after annealing and subsequent additional deformation. Analysis of microstructure evolution during annealing and subsequent additional deformation shows that the key microstructure parameter which is responsible for AIH and DIS effect is the change of dislocation density in grain interior in ECAP þ CR Al, whereas in HPT Al the effects are related to the change of dislocation density at/near grain boundaries. In addition, outstanding combination of high strength (~210 MPa), high electrical conductivity (~62 %IACS) with sufficiently good ductility (7 e10 %) and thermal stability (up to 150°C, at least) was achieved for ECAP þ CR Al after annealing at 150 °C, 1h. [ABSTRACT FROM AUTHOR]

The influence of additional deformation heat treatments (DHTs), implemented by two regimes: (1) annealing and small additional deformation by high-pressure torsion (HPT) at room temperature (RT) and (2) HPT at elevated temperature to 10 turns and small additional HPT at RT, has been studied on the microstructure, mechanical properties and electrical conductivity of ultrafine-grained (UFG) Al-0.53Mg-0.27Zr (wt.%) alloy structured by HPT to 10 turns at RT. As is shown, both types of additional DHT lead to a substantial increase in plasticity (2–5 times) while maintaining high electrical conductivity (~53% IACS) and strength comprising 75–85% of the value in the pre-DHT state of the UFG alloy. The possible physical reasons for the revealed changes in the physical and mechanical properties are analyzed. Comparison of the strength and plasticity changes with the microstructure evolution after DHT of both types indicates that the increase in the density of introduced grain boundary dislocations is the most probable factor providing a tremendous increase in plasticity while maintaining a high level of strength in the UFG alloy under study. An outstanding combination of high strength (370 MPa), high elongation to failure (~15%) and significant electrical conductivity (~53% IACS) was achieved for the Al-Mg-Zr alloy. This combination of properties exceeds those obtained to date for this system, as well as for a number of other commercial conductor alloys based on the Al-Zr system. [ABSTRACT FROM AUTHOR]

This paper presents an overview of fundamentals and potential applications of ultrafine-grained Al-based conductors developed with the help of severe plastic deformation (SPD) techniques. Based on deliberate formation of nanoscale features (such as nanoprecipitates, segregation of solutes along crystallographic defects and so on) within ultrafine grains, it is possible to optimise their mechanical and functional performance enhancing the combination of strength and electrical conductivity to produce advanced lightweight conductors required by modern industries. Guidelines related to SPD-driven development of Al alloys with properties superior to those exhibited by traditionally processed conductors are discussed. [ABSTRACT FROM AUTHOR]

This paper features the changes in microstructure and properties of an Al–Fe alloy produced by casting with different solidification rates followed by severe plastic deformation and rolling. Particularly, different states of the as-cast Al–1.7 wt.% Fe alloy, obtained by conventional casting into a graphite mold (CC) and continuous casting into an electromagnetic mold (EMC), as well as after equal-channel angular pressing and subsequent cold rolling, were studied. Due to crystallization during casting into a graphite mold, particles of the Al6Fe phase are predominantly formed in the cast alloy, while casting into an electromagnetic mold leads to the formation of a mixture of particles, predominantly of the Al2Fe phase. The implementation of the two-stage processing by equal-channel angular pressing and cold rolling through the subsequent development of the ultrafine-grained structures ensured the achievement of the tensile strength and electrical conductivity of 257 MPa and 53.3% IACS in the CC alloy and 298 MPa and 51.3% IACS in the EMC alloy, respectively. Additional cold rolling led to a further reduction in grain size and refinement of particles in the second phase, making it possible to maintain a high level of strength after annealing at 230 °C for 1 h. The combination of high mechanical strength, electrical conductivity, and thermal stability can make these Al–Fe alloys a promising conductor material in addition to the commercial Al–Mg–Si and Al–Zr systems, depending on the evaluation of engineering cost and efficiency in industrial production. [ABSTRACT FROM AUTHOR]

The effect of scandium content and annealing regimes on the properties of cold-rolled sheets from 1580 to 1581 alloys has been studied. The relevance of research is caused by the need to reduce the cost of alloys of the AleMg system with the addition of Sc by reducing the concentration of this element in them without a significant decrease in strength. The initial workpieces for research were ingots of three compositions of alloy 1580 with scandium content from 0.05 to 0.1% (wt.), an ingot of alloy 1581 with 0.03% (wt.) scandium, as well as an ingot of alloy 5083, which is an analogue of alloys 1580 and 1581, but without scandium. Ingots with a cross section of 60 x 200 mm were obtained on a physical model of a semi-continuous casting unit (SCCU) in the laboratory of the Siberian Federal University. Then, according to the regime obtained at the semi-continuous casting unit, a large-sized ingot with a cross section of 560 mm x 1310 mm was cast under industrial conditions. Ingots of the same size 40 mm x 120 mm x 170 mmwere cut from laboratory and industrial ingots, and annealed according to a two-stage regime: the first heating at 350 °C, 3 h, the second heating at 425 °C, 4 h, and subjected to hot rolling with heating up to 450 °C to thickness 5 mm. Then the strips were annealed at 380 °C for 1 h, rolled at room temperature to a thickness of 3 mm, and annealed at temperatures of 250, 275, 300, and 350 °C. Tensile tests of samples made from sheets of 1580 and 1581 alloys after annealing in the temperature range of 250 e300 °C showed that they surpass alloy 5083 in strength properties by no less than 10%. Studies of the cast and deformed structure of alloys 1580 and 1581, carried out by the methods of light, scanning and transmission electron microscopy revealed that during annealing dispersed particles of the Al3(Sc, Zr) phase precipitate from the solid solution of ingots, which, during deformation of the alloys and subsequent technological heating associated with hot rolling and annealing, contribute to the formation and preservation of a subgrain structure in sheet semi-finished products. This factor prevents the occurrence of recrystallization and ensures the strengthening of deformed semi-finished products. [ABSTRACT FROM AUTHOR]

This study aims to achieve an ultrafine-grained (UFG) Al 2024 alloy superplasticity at temperatures lower than the traditional ones for commercial Al alloys (400–500 °C). The UFG structure with a mean grain size of 100 nm produced in the alloy by high-pressure torsion at room temperature provided a very high strength—microhardness (HV0.1) of 286 ± 4, offset yield strength (σ0.2) of 828 ± 9 MPa, and ultimate tensile strength (σUTS) of 871 ± 6 MPa at elongation to failure (δ) of 7 ± 0.2%. Complex tensile tests were performed at temperatures from 190 to 270 °C and strain rates from 10−2 to 5 × 10−5 s−1, and the values of flow stress, total elongation and strain rate-sensitivity coefficient were determined. The UFG alloy was shown to exhibit superplastic behavior at test temperatures of 240 and 270 °C. For the first time, 400% elongation was achieved in the alloy at an unusually low temperature of 270 °C (0.56 Tm) and strain rate of 10−3 s−1. The UFG 2024 alloy after superplastic deformation was found to have higher strength (150–160 HV) than that after the standard strengthening heat treatment T6. [ABSTRACT FROM AUTHOR]

The influence of decreased temperature of tensile testing on annealing-induced hardening (AIH) and deformation-induced softening (DIS) effects has been studied in an ultrafine-grained (UFG) Al–Zr alloy produced by high-pressure torsion. We show that the UFG Al–Zr alloy demonstrates a DIS effect accompanied by a substantial increase in the elongation to failure δ (up to δ ≈ 30%) depending on the value of additional straining. Both the AIH and DIS effects weaken with a decrease in the tensile test temperature. The critical deformation temperatures were revealed at which the AIH and DIS effects are suppressed. The activation energy Q of plastic flow has been estimated for the UFG Al–Zr alloy in the as-processed, subsequently annealed and additionally strained states. It was shown that the annealing decreases the Q-value from ~80 kJ/mol to 23–28 kJ/mol, while the subsequent additional straining restores the initial Q-value. Alloying with Zr results in the expansion of the temperature range of the AIH effect manifestation to lower temperatures and results in the change in the Q-value in all of the studied states compared to the HPT-processed Al. The obtained Q-values and underlying flow mechanisms are discussed in correlation with specific microstructural features and in comparison to the UFG Al. [ABSTRACT FROM AUTHOR]

The paper reports on the features of low-temperature superplasticity of the heat-treatable aluminum Al-Mg-Si alloy in the ultrafine-grained state at temperatures below 0.5 times the melting point as well as on its post-deformation microstructure and tensile strength. We show that the refined microstructure is retained after superplastic deformation in the range of deformation temperatures of 120–180 °C and strain rates of 5 × 10–3 s–1–10–4 s–1. In the absence of noticeable grain growth, the ultrafine-grained alloy maintains the strength up to 380 MPa after SP deformation, which considerably exceeds the value (250 MPa) for the alloy in the peak-aged coarse-grain state. This finding opens pathways to form high-strength articles of Al-Mg-Si alloys after superplastic forming. [ABSTRACT FROM AUTHOR]

Low temperature tensile and impression creep tests were carried out on an ultrafine-grained 7xxx series Al–4.8Zn–1.2 Mg–0.14Zr (wt%) alloy, which can be deformed for maximum elongation of about 200% at 150 °C. The characteristics of the deformation process, such as the strain rate sensitivity (SRS) and activation energy (Q) were determined by considering also the effect of threshold stress. Relatively high SRS of ∼ 0.35 and low activation energy of ∼ 92 kJ/mole were obtained, confirming the super ductility of the investigated ultrafine-grained alloy in the low temperature region between 140 and 160 °C. [ABSTRACT FROM AUTHOR]

The important benefits of ultrafine-grained (UFG) alloys for various applications stem from their enhanced superplastic properties. However, decreasing the temperature of superplasticity and providing superplastic forming at lower temperatures and higher strain rates is still a priority. Here, we disclose, for the first time, the mechanism by which grain boundary sliding and rotation are enhanced, when UFG materials have grain boundary segregation of specific alloying elements. Such an approach enables achieving superplasticity in commercial Al alloys at ultralow homologous temperatures below 0.5 (i.e. below 200°C), which is important for developing new efficient technologies for manufacturing complex-shaped metallic parts with enhanced service properties. For the first time, ultralow-temperature superplasticity is found in commercial 7xxx Al alloy. This discovery enables the development of new technologies for the superplastic forming of complex-shaped products with enhanced service properties. [ABSTRACT FROM AUTHOR]

An ultrafine-grained (UFG) Al-4.8%Zn-1.2%Mg-0.14%Zr (wt%) alloy was processed by high pressure torsion (HPT) technique and then aged at 120 and 170 °C for 2 h. The changes in the microstructure due to this artificial aging were studied by X-ray diffraction and transmission electron microscopy. It was found that the HPT-processed alloy has a small grain size of about 200 nm and a high dislocation density of about 8 × 1014 m−2. The majority of precipitates after HPT are Guinier–Preston (GP) zones with a size of ~ 2 nm, and only a few large particles were formed at the grain boundaries. Annealing at 120 and 170 °C for 2 h resulted in the formation of stable MgZn2 precipitates from a part of the GP zones. It was found that for the higher temperature the fraction of the MgZn2 phase was larger and the dislocation density in the Al matrix was lower. The changes in the precipitates and the dislocation density due to aging were correlated to the hardness evolution. It was found that the majority of hardness reduction during aging was caused by the annihilation of dislocations and some grain growth at 170 °C. The aging effect on the microstructure and the hardness of the HPT-processed specimen was compared to that observed for the UFG sample processed by equal-channel angular pressing. It was revealed that in the HPT sample less secondary phase particles formed in the grain boundaries, and the higher amount of precipitates in the grain interiors resulted in a higher hardness even after aging. [ABSTRACT FROM AUTHOR]

High‐pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high‐pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high‐pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High‐pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys. [ABSTRACT FROM AUTHOR]

Three different Al-Zn alloys (2, 10, 30 wt% Zn) have been processed by severe plastic deformation (SPD) in the solutionized state to investigate the concomitant mechanisms of grain refinement and phase separation. The data of high resolution analytical transmission electron microscopy clearly reveal the key role of grain boundaries that promote Zn segregation and fast diffusion. Surprisingly, it is also shown that SPD carried out at 150 °C could give rise to a finer multiphase structure comparing to room temperature processing. Our observations seem to indicate that it resulted from a competition between the classical discontinuous precipitation of Zn and SPD-induced dynamic precipitation. [ABSTRACT FROM AUTHOR]

This paper investigates a dynamic aging effect induced by severe plastic deformation (SPD) and subsequent artificial aging on structure and mechanical properties of aluminum Al-Mg-Si alloys. Application of optimal processing parameters of SPD via equal-channel angular pressing with parallel channels and subsequent artificial aging ensures simultaneous enhancement of strength and ductility in the processed alloys. Ultrafine-grained microstructures with strengthening metastable β' and β'' precipitates generated during SPD processing and subsequent artificial aging provide enhanced strength due to significant grain boundary hardening and precipitation hardening. [ABSTRACT FROM AUTHOR]

This paper studies the effect of equal channel angular pressing-Conform (ECAP-C) and further artificial aging (AA) on microstructure, mechanical, and electrical properties of Al 6101 alloy. As is shown, ECAP-C at 130 °C with six cycles resulted in the formation of an ultrafine-grained (UFG) structure with a grain size of 400--600 nm containing nanoscale spherical metastable β' and stable β second-phase precipitates. As a result, processed wire rods demonstrated the ultimate tensile strength (UTS) of 308 MPa and electrical conductivity of 53.1% IACS. Electrical conductivity can be increased without any notable degradation in mechanical strength of the UFG alloy by further AA at 170 °C and considerably enhanced by additional decomposition of solid solution accompanied by the formation of rod-shaped metastable β' precipitates mainly in the ultrafine grain interior and by the decrease of the alloying element content in the Al matrix. It is demonstrated that ECAP-C can be used to process Al-Mg-Si wire rods with the specified UFG microstructure. The mechanical strength and electrical conductivity in this case are shown to be much higher than those in the industrial semi-finished products made of similar material processed by the conventional T6 or T81 treatment. [ABSTRACT FROM AUTHOR]

The paper presents the evaluation of the mechanical and fatigue properties of an ultrafine-grained (UFG) Al 6061 alloy processed by high-pressure torsion (HPT) at room temperature (RT). A comparison is made between the UFG state and the coarse-grained (CG) one subjected to the conventional aging treatment T6. It is shown that HPT processing leads to the formation of the UFG microstructure with an average grain size of 170 nm. It is found that yield strength (σ0.2), ultimate tensile strength (σUTS) and the endurance limit (σf) in the UFG Al 6061 alloy are higher by a factor of 2.2, 1.8 and 2.0 compared to the CG counterpart subjected to the conventional aging treatment T6. Fatigue fracture surfaces are analyzed, and the fatigue behavior of the material in the high cycle and low cycle regimes is discussed. [ABSTRACT FROM AUTHOR]

Structural features, microhardness, and mechanical properties of three binary Al-Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion at room temperature were comparatively investigated using transmission electron microscopy, high-resolution transmission electron microscopy, and quantitative X-ray diffraction measurements. Average grain sizes measured by dark-field images are in the range 71-265 nm while the sizes of coherent domains decreased tremendously from 86 to 46 nm as the Mg content increased from 0.5 to 4.1 wt%. The average dislocation density in the deformed alloys is in the range 0.37 × 10-4.97 × 10 m. Both the microhardness and tensile strength of all the deformed alloys increased dramatically as compared to the undeformed counterparts. The yield strength with values ranging from 390 to 690 MPa in the deformed alloys is typically five to seven times higher than that of the same undeformed alloys. Calculations based on the Hall-Petch and Taylor equations suggest that the strengthening mechanisms contributing to the very high strength may depend not only on the conventional mechanisms of grain size strengthening and dislocation strengthening, but also on the additional mechanisms related to the contributions from stacking faults and nanotwins, and nonequilibrium GBs observed in the deformed alloys. [ABSTRACT FROM AUTHOR]

Grain boundary (GB) segregations were investigated by atom probe tomography in an Al-Mg alloy, a carbon steel and Armco® Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminum alloy are Mg depleted, but after SPD some local enrichment up to 20 at% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as 'non-equilibrum' in ultra fine grained materials processed by SPD. The GB segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms. [ABSTRACT FROM AUTHOR]

Processing by severe plastic deformation (SPD) typically increases the strength of metals and alloys drastically by decreasing their grain size into the submicrometer or nanometer range but the ductility of such materials remains typically low. This report describes the first demonstration that it is possible to increase the room temperature ductility of aluminum-based alloys processed by SPD and to attain elongations to failure of >150% while retaining the enhanced strength. This unique combination of properties is due to the occurrence of grain boundary sliding at room temperature. The sliding was obviously achieved by introducing a grain boundary wetting of the aluminum/aluminum grain boundaries. [ABSTRACT FROM AUTHOR]

Nanostructures of three binary Al–Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion at room temperature were comparatively investigated using transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray line profile analysis. Grain size distributions, dislocation densities, and densities of planar defects including stacking faults and microtwins were quantified. The average subgrain size decreased considerably from 120 to 55 nm as the Mg content increased from 0.5 to 4.1 wt%. The average dislocation density in the alloys first increased to a maximum and then decreased as the Mg content increased and the average subgrain size decreased. The role of Mg solute on these features and the refinement mechanisms associated with the typical nanostructures and faults were interpreted. [ABSTRACT FROM AUTHOR]

The concept of grain boundary (GB) engineering of ultrafine-grained (UFG) metals and alloys is developed for enhancement of their properties by tailoring different GBs (low-angle and high-angle ones, special and random, or equilibrium and nonequilibrium) and formation of GB segregations and precipitations by severe plastic deformation (SPD) processing. In this article, using this approach and varying regimes and routes of SPD processing, we show for several light alloys (Al and Ti) the ability to produce UFG materials with different GBs, and this can have a dramatic effect on the mechanical behavior of the processed materials. This article demonstrates also several new examples of attaining superior strength and ductility as well as enhanced superplasticity at low temperatures and high strain rates in various UFG metals and alloys. [ABSTRACT FROM AUTHOR]

Microstructural features and mechanical properties of an Al-Mg-Si alloy processed by high-pressure torsion (HPT) have been investigated using transmission electron microscopy, X-ray diffraction, three-dimensional atom probe, tensile tests and micro-hardness measurements. It is shown that HPT processing of the Al-Mg-Si alloy leads to a much stronger grain size refinement than of pure aluminium (down to 100 nm). Moreover, massive segregation of alloying elements along grain boundaries is observed. This nanostructure exhibits a yield stress even two times higher than that after a standard T6 heat treatment of the coarse-grained alloy. [ABSTRACT FROM AUTHOR]

This study focuses on the difference in microstructural features and physical properties of Al-2Fe and Al-4Fe alloys subjected to large plastic straining. The difference in the intermetallic particle morphology in the initial state is shown to be a key parameter influencing the particle and grain fragmentation process and, as a result, the properties of these two alloys. We demonstrate that the shape and average size of Al-Fe intermetallic particles provide stronger effect on the microstructure evolution during high pressure torsion (HPT) than their volume fraction. The formation of Fe supersaturated solid solution in Al in these two alloys during deformation is discussed in connection to the morphology of the intermetallic phase. The major microstructural attributes, responsible for the solid solution formation, are highlighted. [ABSTRACT FROM AUTHOR]

Experimental aluminum alloy containing 0.8% Ca, 0.5% Zr, 0.5% Fe and 0.25% Si (wt.%), in the form of a long-length rod 12 mm in diameter was manufactured using an electromagnetic casting (EMC) technique. The extremely high cooling rate during alloy solidification (≈104 K/s) caused the formation of a favorable microstructure in the ingot characterized by a small size of the dendritic cells, fine eutectic particles of Ca-containing phases and full dissolution of Zr in Al the solid solution. Due to the microstructure obtained the ingots possess high manufacturability during cold forming (both drawing and rolling). Analysis of the electrical conductivity (EC) and microhardness of the cold rolled strip and cold drawn wire revealed that their temperature dependences are very close. The best combination of hardness and EC in the cold rolled strip was reached after annealing at 450 °C. TEM study of structure evolution revealed that the annealing mode used leads to the formation of L12 type Al3Zr phase precipitates with an average diameter of 10 nm and a high number density. Experimental wire alloy has the best combination of ultimate tensile strength (UTS), electrical conductivity (EC) (200 MPa and 54.8% IACS, respectively) and thermal stability (up to 450 °C) as compared with alloys based on the Al–Zr and Al– rare-earth metal (REM) systems. In addition, it is shown that the presence of calcium in the model alloy increases the electrical conductivity after cold forming operations (both drawing and rolling). [ABSTRACT FROM AUTHOR]

The method of electromagnetic casting (EMC) was used to produce the long-length rod billet (with a diameter 12 mm) of aluminum alloy containing 0.6 wt.% Zr, 0.4%Fe, and 0.4%Si. The combination of high cooling rate (≈104 K/s) during alloy solidification and high temperature before casting (≈830 °C) caused zirconium to dissolve almost completely in the aluminum solid solution (Al). Additions of iron and silicon were completed in the uniformly distributed eutectic Al8Fe2Si phase particles with an average size of less than 1 µm. Such fine microstructure of the experimental alloy in as-cast state provides excellent deformability during wire production using direct cold drawing of EMC rod (94% reduction). TEM study of structure evolution in the as-drawn 3 mm wire revealed the onset of Al3Zr (L12) nanoparticle formation at 300 °C and almost-complete decomposition of (Al) at 400 °C. The distribution of Zr-containing nanoparticles is quite homogeneous, with their average size not exceeding 10 nm. Experimental wire alloy had the ultimate tensile strength (UTS) and electrical conductivity (EC) (234 MPa and 55.6 IACS, respectively) meeting the AT2 type specification. At the same time, the maximum heating temperature was much higher (400 versus 230 °C) and meets the AT4 type specification. [ABSTRACT FROM AUTHOR]

Herein, the characterization of microstructures and mechanical properties of Al–Zn alloys ultrafine‐grained (UFG) by using high pressure torsion (HPT) is surveyed. Emphasis is placed on the decomposition of the solid solution structures due to the HPT process, leading to unique mechanical and plastic properties of the UFG alloys. The decomposed microstructures, the grain boundaries wetted by Zn‐rich layers, as well as the softening, grain boundary sliding (GBS) with usually high strain rate sensitivity and super‐ductility of the HPT‐processed samples are described and discussed. Furthermore, the innovation potential of intensive GBS at room temperature is briefly considered. [ABSTRACT FROM AUTHOR]

Herein, the ultrafine‐grained (UFG) 7xxx series alloy Al–4.8Zn–1.2Mg–0.14Zr demonstrates superplasticity at unusually low temperatures of 120–170 °C while maintaining its high‐strength state. The UFG structure is formed by high pressure torsion (HPT) at room temperature (RT), which leads to a considerable increase in the strength characteristics by ≈60% compared with the material after conventional heat treatment T6. It is found that the UFG alloy exhibits thermostability when testing or annealing up to 170 °C. Deforming by tensile test at a strain rate of 10−4 s−1 and 10−3 s−1, the elongation to failure at 120 and 170 °C exceeds 250% and 500%, respectively, whereas the strain rate sensitivity reaches 0.45, which is a typical value characterizing superplastic deformation. After superplastic deformation, the UFG alloy maintains 25–50% higher strength characteristics at RT than that after conventional heat treatment T6. The origin of such superior behavior of the UFG alloy is discussed. [ABSTRACT FROM AUTHOR]

This study aims to achieve high ductility at lower temperatures (170 and 200 °C) while retaining enhanced mechanical strength in the ultrafine‐grained high‐strength Al‐based alloy 7475. The ultrafine grain structure is formed by high pressure torsion (HPT) at room temperature. Isochronous annealing in a range of temperatures from 80 to 450 °С demonstrated that the high hardness values are retained or change insignificantly up to 200 °С. Static testing was performed at 120–200 °С and strain rates from 10−2 to 10−4 s−1 to determine the ductility and strain rate sensitivity. Elongations of 500% is achieved at 170 °С and a strain rate of 10−3 s−1, and of 700% at 200 °С and a strain rate of 5 × 10−4 s−1. The work focuses on deformation behavior of UFG 7475 alloy in terms of thermal stability of the high‐strength state to detect the signs of superplastic deformation exhibited by the material. Elongations of 500% at 170 °С and 700% at 200 °С have been registered as well as a strain rate of 10−3 s−1 and that of 5 × 10−4 s−1. [ABSTRACT FROM AUTHOR]

This paper focuses on the mechanical properties, electrical conductivity and fatigue performance of ultra-fine-grained (UFG) Al-Mg-Si wires processed by a complex severe plastic deformation route. It is shown that the nanostructural design via equal channel angular pressing (ECAP) Conform followed by heat treatment and cold drawing leads to the combination of enhanced tensile strength, sufficient ductility, enhanced electrical conductivity, and improved fatigue strength compared to the wires after traditional T81 thermo-mechanical treatment used in wire manufacturing. The Processing-microstructure-properties relationship in the studied material is discussed. [ABSTRACT FROM AUTHOR]

Samples of commercially received aluminum AA6101 alloy are homogenized, quenched, and subjected to 2, 4, and 8 passes of Equal Channel Angular Pressing (ECAP) with 200 MPa of applied backpressure. Tensile strength of the alloy's samples increases with the accumulated strain to the double value of 400 MPa after 8 ECAP passes, while electrical conductivity slightly decreases from 51.3 to 48.2%IACS. Aging at 130 °C for 72 h is used to restore conductivity with very small loss of strength. Moreover, the increase in conductivity is directly proportional to the number of ECAP passes and conductivity exceeds those values measured for the as‐received and solution treated states. Strong inhomogeneity of the microstructure and formation of a network of differently oriented shear bands during severe plastic deformation is observed, which is beneficial for simultaneous enhancement of mechanical and electrical properties. ECAP with back pressure results in nonuniform microstructure consisting of the intersecting shear bands with grains of 200 nm and inter‐bands matrix with large grains about 10–20 μm. Aging at 130 °C leads to precipitation of plate and needle like particles within shear bands and spherical particles within matrix, providing tensile strength of 340 MPa and electrical conductivity of 54.1 % IACS. [ABSTRACT FROM AUTHOR]