Search

In this research, the accumulative roll bonding (ARB) technique was employed as a severe plastic deformation method to manufacture a unique bi-metal Pb/W composite reinforced by Co 3 O 4 ceramic oxide. For this purpose, composites with different amounts of reinforcement particles (0.25, 0.5, 1, 1.5, and 2 wt%) were successfully produced using the ARB process (up to 10 cycles). Also, the mechanical properties were evaluated using microhardness, tensile, and shear punch tests. For microstructural investigations, the X-ray diffraction method (XRD), transmission electron microscopy (TEM), and fractography analysis by scanning electron microscopy (SEM) were employed. The Pb-0.5%W/Co 3 O 4 following 10 ARB cycles exhibited optimal mechanical and microstructural properties. For this composite, the tensile strength showed a markable increase of 2.17 times, yield strength by 4.7 times, shear strength by 3.6 times, and hardness by 4.2 times compared to the pure Pb sample subjected to the same ARB cycles. However, the strain was reduced by 3.85 times. These enhanced properties are also followed by increased stiffness and improved anode dimensional stability, creep resistance, and operational lifespan. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, Al/18Cu/3WC/3MoS 2 (wt.%) multilayered hybrid composites were fabricated by accumulative roll bonding (ARB), and their electrical and mechanical properties were investigated. After seven ARB cycles, an Al-matrix multilayered hybrid composite with a uniform distribution of WC-MoS 2 particles and Cu islands was achieved. The presence of the WC-MoS 2 particles and Cu islands significantly affected the electrical and mechanical properties of the fabricated composites. The composite obtained after seven ARB cycles showed an enhanced strength of 259 MPa. Also, it was found that the electrical conductivity of the Al matrix decreased by applied strain (about 19 % IACS) and the presence of the WC-MoS 2 particles. By annealing the fabricated composite obtained from final cycles, the electrical conductivity increased from 54 % IACS to 71 % IACS. [ABSTRACT FROM AUTHOR]

This article concerns the effect of strain accumulation during low-cycle fatigue on the post-fatigue tensile behavior of metal matrix composites (MMCs) with identical layers of aluminum reinforced by Fe 3 O 4 nanoparticles produced via the accumulative roll bonding (ARB) technique. Work-hardening behavior, deduced from ratcheting curves, was evaluated by the post-fatigue tensile test. The key finding in the mechanical properties of homogeneous nanocomposite in terms of reinforcement distribution, evolving due to microstructural evolution during the ARB process, is that accumulation of ratcheting strain decreases, and fatigue and post-fatigue tensile behavior significantly increases. The rupture mechanism, analyzed by scanning electron microscope, revealed that deep hemispherical-shaped dimples, a well-known feature of ductile rupture, were changed to elongated shallow shear dimples by the impact of microstructural evolution due to imposed 1000 cycles of ratcheting test. [ABSTRACT FROM AUTHOR]

The study examined how various annealing methods affect the structure and characteristics of Al/Zn layered composite plates. Four distinct composite plates underwent annealing at temperatures of 160 °C, 200 °C, and 240 °C for durations ranging from 0.5 h, 1 h, 1.5 h, and 2 h. Changes in grain structure, interface appearance, and thickness of the interface diffusion layer were analyzed using metallographic microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Tensile and microhardness tests were performed under different annealing conditions and cycling durations. Results showed that as annealing time increased, tensile strength initially rose before declining, while elongation remained consistently high. The optimal balance between strength and ductility was observed at 200 °C for 1.5 h of annealing across all plate types. Before annealing, Al displayed a fractured ultrafine crystalline structure, while Zn's texture underwent changes. [ABSTRACT FROM AUTHOR]

The interface evolution of Ti/Ni multi-layered composites produced by accumulative roll bonding after heat treatment was investigated in this study. The influence of heat treatment temperature on the microstructure and chemical composition of the Ti/Ni interfaces were examined by scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy system (EDS) and transmission electron microscope (TEM). Phase composition and transition behavior of interfaces of the Ti/Ni multi-layered samples were studied by X-ray diffraction (XRD) and a differential scanning calorimeter (DSC). Only from the viewpoint of ΔG, ignoring the impact of other factors, the formation sequence of Ti–Ni IMCs is TiNi 3 →Ti 2 Ni→TiNi at the beginning of the diffusion reaction. With temperature increases, the microstructure of the composite is a mixture structure with alternating TiNi and Ti 2 Ni layers and the boundary morphology of each diffusion sub-layer transforming from an initial smooth and clear boundary, to the flocculent structure of the TiNi and Ti 2 Ni transition layer. The DSC results revealed a good martensitic and reverse transformation behavior from B2 to B19' of Ms at around 64 °C. With temperature increases, the austenite transformation temperature (T A) slowly shifts to high temperature and the change of martensite transformation temperature (T M) is not obvious. The phase transition hysteresis (A p -M p) from 5.9 °C of the 550 °C × 10 h heat treatment sample increases to 33 °C of the 770 °C × 10 h sample. • Ti/Ni multi-layer composites of Ti rich have been successfully fabricated by ARB. • Microstructure of Ti/Ni composites from layer changed to TiNi and Ti 2 Ni hybrid. • A martensitic transformation behavior from B2 to B19' appeared. [ABSTRACT FROM AUTHOR]

Abstract In this paper, an accumulative roll bonding (ARB) process is exploited to produce high-strength, fine dispersed and uniform distribution of Al-5vol.%SiC nanocomposite. The microstructure illustrates and validates a good distribution of SiC reinforced in the Al 1050 matrix. It is observed that, an increasing of ARB passes tends to decrease and refine the size of SiC particle to nanoscale. It is concluded from tensile test that, as number of passes increases, strengths of Al ARBed and composite samples are improved. However, their ductility decreases at initial ARB pass and then increased. The Al-SiC tensile strength of nanocomposite sample is greater 5 times than the annealed Al 1050 used as the original raw material. The strengthening of composite sample occurs due to grain refinement, uniformity, reinforcing role of particles, strain work hardening, and bonding quality. From hardness test, after the initial pass, the hardness improved quickly, then dwindled and finally saturated by further rolling. Experimental data is exploited to derive governing equations describe the effect of the number of ARB passes on the tensile strength and elongation of manufactured nanocomposite samples. It is found that, the tensile strength and elongation can be described as an exponential function that depends on the number of passes. Numerical results from these equation are more consistent with experimental investigation. Highlights • ARB technique is used to produce highly uniform Al-SiC nanocomposites. • The tensile strength and elongation can be described by exponential functions, those depend on the number of ARB passes. • Tensile strength and microhardness became 4 and 3 times larger than Al. • Grain refinement, dislocation strengthening are the main strengthening mechanisms. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Slightly increased monotonic strength but clearly enhanced ductility of the aluminum/steel composite. • Significant enhanced fatigue lives of the aluminum/steel composite at low and high stress amplitudes. • Pronounced crack branching at the aluminum/steel material interface at higher stress amplitudes. • Effective load transfer from the outer aluminum layer into the inner steel layers at low stress amplitudes. Abstract The accumulative roll bonding process allows to produce multilayered composites in which substantially dissimilar metals, both in terms of Young's modulus as well as mechanical strength, can be brought together. For the optimization of such laminated metal composites a fundamental understanding of the microstructural interactions and deformation processes at the internal material interfaces is necessary. The influence of a gradient in hardness and Young's modulus in ultrafine-grained laminated metal composites on the monotonic and cyclic mechanical properties is investigated in this paper. Special attention is put on aluminum/steel composites, as a high gradient in hardness and Young's modulus is present at the layer interfaces. The mechanical properties are determined in monotonic and cyclic three-point bending tests. By scanning electron microscopy, the influence of the meso- and microstructure on the fatigue properties is intensively studied. Furthermore, the internal stresses during elastic straining are calculated using finite element simulations. The results are that for the aluminum/steel composites the monotonic and cyclic properties are drastically increased compared to aluminum mono-material sheets, as well as to composites based on two different aluminum alloys, in which only a gradient in hardness at the material interface exists and the gradient in elastic properties is absent. This is related to a pronounced crack deviation at the material interface as well as to an effective load transfer in the composites. [ABSTRACT FROM AUTHOR]

High damping capacity and low density M2052/Al composites were successfully fabricated using the accumulative roll bonding (ARB) method, by taking advantages of high damping capacity for M2052 alloy (Mn-20Cu-5Ni-2Fe, at%) particles and excellent mechanical properties and low density for Al matrix. The 15 wt% M2052 particles were uniformly dispersed in Al-matrix after 10 ARB process cycles. M2052/Al composites have a low density of 2.9 g/cm 3 , which is just a little higher than that of Al. After ARB process and a subsequent hydrogen annealing, the M2052/Al composites exhibit both high room temperature damping capacity and good mechanical properties: the highest damping capacity is 0.01 at 270 K, 5 times that of pure Al at the comparative temperature; the ultimate tensile strength is about 70 MPa (about 35% higher than that of pure Al), and the total elongation reaches 24%. The simultaneous enhancements on damping capacity and tensile strength of the M2052/Al composites can be attributed to the high damping capacity and the dispersion strengthening of M2052 phase, as well as the good bonding between the M2052 particles and Al matrix resulted from the ARB technique. [ABSTRACT FROM AUTHOR]

In the present research, Zn/Sn composites were produced for the first time by accumulative roll bonding (ARB) process up to seven cycles. The microstructure evolution was evaluated by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and the mechanical properties of Zn/Sn multilayered composites were measured by Vickers microhardness and tensile tests at different cycles of ARB process. It was observed that by increasing the ARB cycles, due to the differences in the mechanical behavior of the layers, Zn layers were necked at first, fractured and dispersed between Sn layers. After seven ARB cycles, a laminated composite with wavy interfaces and homogeneously distributed lenticular fragments of Zn was achieved. The XRD results showed that no new phase has been formed during the ARB process. Fracture surfaces of the samples after tensile tests were observed by SEM. Fracture surfaces revealed that fracture mode for the Zn layers was brittle at all cycles and fracture mode for the Sn layers was ductile at initial cycles and then changed to shear ductile fracture by increasing the ARB cycles. [ABSTRACT FROM AUTHOR]

The evolution of microstructure together with mechanical properties change of Fe-28.5Ni steel, used in design of marine and nuclear related products, processed by different deformation amount during ARB process was elaborated by Electron Backscattered Diffraction (EBSD) method. EBSD results showed that the initial structure of the material contained retained austenite as the main phase besides martensite phase. Martensite phase was diminished after successive ARB cycles due to reduction of martensite start (M s ) temperature. EBSD microstructural results exhibited that a stabilized nano structure was attained by 6-cycle or 8-cycle of the ARB process with the latter having slightly higher grain size due to the grain growth effect of dynamic restoration mechanism resulting from extreme deformation. Tensile test data on different cycles of ARB processed specimens showed that yield and ultimate tensile strengths were substantially increased after the first cycle of the ARB coinciding with the substantial amount of dislocations in the form of low angle grain boundaries (LAGB). Strengths increased in the successive cycles, though in a much slower pace. Ultra-fine grains were formed instead after high cycles of ARB process. Although such increase in strength generally came at the expense of ductility, the material after 8-cycle had still substantial ductility. [ABSTRACT FROM AUTHOR]

The influence of the layer architecture on the fatigue properties of ultrafine-grained laminated metal composites is studied. Composites with different stacking sequences of the aluminum alloys AA1050, AA5005, and AA2024 were produced by accumulative roll bonding and characterized by microstructural analysis and nanoindentation experiments. The fatigue properties were determined by 3-point bending tests performed on a vibraphore testing machine. Subsequently, the crack path was analyzed using a scanning electron microscope. It was observed that the fatigue crack bifurcates close to the interface if the hardness difference between both materials is high. The crack then spreads parallel to the interface within the softer material. This crack branching is more pronounced at high stress amplitudes caused by a significant accumulation of plastic deformation in front of the interface. Consequently, at high stress amplitudes the fatigue lives are significantly higher for composites with a high hardness difference between the layers. At low stress amplitudes, at which crack initiation is the dominating fatigue mechanism, the material of the outer layer mainly determines the fatigue lives. Composites with the same outer layer, but different interlayers, show very similar high cycle fatigue lives. Thus, by an appropriate layer architecture ultrafine-grained laminated metal composites with significantly enhanced fatigue properties can be designed. [ABSTRACT FROM AUTHOR]

In this study, the effect of accumulative roll bonding (ARB) process on the microstructure, deformation texture and mechanical properties of AA2024 strip was investigated. Microstructural observations were done by electron backscattering diffraction (EBSD) technique and scanning electron microscopy (SEM). Also, mechanical properties were performed by uniaxial tensile and microhardness tests. It was observed that accumulative roll bonding is a promising process for production of nano/ultrafine grained (NG/UFG) 2024 aluminum alloy after seventh ARB cycles, reaching grain sizes of smaller than 120 nm. The fraction of high angle grain boundaries and mean misorientation were represented increased by increasing the strain during the ARB process and reached to a saturated value of 64% and 25.37°, respectively. Deformation texture evolution demonstrated that the formation of nano shear bands at the final ARB cycle was facilitated by the formation of Brass {011}〈211〉 and Goss {011}〈100〉 components. By increasing the number of ARB cycles, the yield strength, tensile strength and microhardness of the ARB processed sample improved and reached to 345 MPa, 450 MPa and 141 HV after 7 cycles, respectively, which were 2.65, 2.40 and 2.23 times higher than obtained values for initial materials, i.e. 130 MPa, 188 MPa and 63.5 HV. After the tensile test, debonding can be observed especially in the interface formed in the last cycle. Observations revealed that the failure mode in the accumulatively roll bonded AA2024 strip was a shear ductile rupture with elongated shallow shear dimples. [ABSTRACT FROM AUTHOR]

In order to fabricate high damping/strength metal matrix composites, hard ceramic particulates Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 (LLZNO) reinforced Al composites were prepared by accumulative roll bonding (ARB) method with intermittent heat treatments. LLZNO particles did not react with Al and were uniformly dispersed in Al-matrix after 10 ARB cycles. With increasing ARB cycles, the ultimate tensile strength of the LLZNO/Al composites increased and reached 132 MPa after 10 ARB cycles, which was 2.5 times that of the pure Al, while the total elongation of LLZNO/Al composites increased from 5% after 1 cycle to 10% after 10 cycles. The maximum damping capacity as high as 0.009 was achieved after 10 ARB cycles in the 10 wt% LLZNO/Al composite at 320 K and 1 Hz, which was 4.5 times that of pure Al. The simultaneous enhancement on damping capacity, tensile strength and ductility of the LLZNO/Al composite around room temperature can be ascribed to the high damping capacity and the dispersion strengthening of the LLZNO phase, as well as the good bonding between the LLZNO particles and Al matrix resulted from the ARB technique. [ABSTRACT FROM AUTHOR]

In this paper, microstructural evolution together mechanical properties variation in a Fe-24Ni (wt%) lath martensitic steel processed by accumulative roll bonding (ARB) and reverse transformation was investigated. The microstructural analysis indicated that after 6-cycle of the ARB process ultrafine/nano structure having mean grain size below 200 nm is obtained. Furthermore, the typical lath martensitic structure transformed to complicated microstructure consisting of ultrafine equiaxed ferrite (α-Fe) as well as ultrafine grains of austenite (γ-Fe). The results also showed that by increasing the number of ARB cycle martensite starting (M s ) temperature decreased. As well, tensile test results showed that both the yield strength and uniform tensile elongation improved considerably by 6-cycle of the ARB process. Increasing uniform elongation can be attributed to stabilization of austenite during the ARB process. [ABSTRACT FROM AUTHOR]

In this study, microstructure development with respect to mechanical properties in ultrafine grained dual phase (martensite/austenite) by chemical composition of Fe-24Ni-0.1C (wt%) steel processed by 1-cycle and 6-cycle of accumulative roll bonding (ARB) process was investigated. Microstructure characterization by electron backscatter diffraction (EBSD) system showed that significant grain refinement occurred after 6 cycles ARB process and an average grain size smaller than 200 nm was obtained. Moreover, phase analysis map obtained from EBSD system showed that the microstructure of starting material is mostly constituted of martensite phase (more than 70%) and transforms to retained austenite by 6 cycles of ARB process. This phenomenon has proved that retained austenite is stabilized during the ARB process through grain refinement. Uniaxial tensile tests exhibited that yield strength did not significantly improve by 1-cycle reverse transformation compared to the starting material. In contrast, further continuation of the ARB process caused gradual increase in yield and ultimate tensile strengths. The significant improvement in yield strength should be originated from significant grain regiment introduced by 6 cycles of the ARB process. Surprisingly, the uniform tensile elongation for the starting material and the 6 cycles ARB processed specimen are almost the same, though yield and ultimate tensile strengths are considerably improved by employing 6 cycles of ARB process. [ABSTRACT FROM AUTHOR]

The high strain deformation and recrystallization behaviour of a Fe/Ni multilayered composite sheet fabricated by accumulative roll bonding has been investigated. The comparable initial hardness and subsequent strain hardening behaviour of the Ni and Fe layers reduces the flow compatibility related challenges at the bonding interfaces, thereby generating parallel layers of uniform thickness during rolling to true strains up to 4.18. Typical body centred cubic ( α- and γ- fibres) and face centred cubic ( β- fibre) rolling textures were generated in the Fe and Ni layers, respectively. During annealing at 700 °C, recrystallization takes place homogenously in the Ni layers but commences initially by particle stimulated nucleation at oxide debris present at the interface of adjacent Fe layers. After recrystallization, the texture of the Ni layers is similar to the starting material prior to ARB, but considerable texture modification occurs in the Fe layers. For both metals, oriented growth of nucleated grains has the greatest influence on the final annealing textures, which generates the classic Cube texture in Ni and a {511}<1 5 10> texture in Fe. While these final textures of the individual Fe and Ni layers are not conducive to good formability, texture-based Schmidt factor calculations of the combined layers show an overall balance in texture components that points to a reduction in planar anisotropy. The ability to fabricate multilayered textured sheets by this route is a promising way of controlling the anisotropy of both strength and ductility. [ABSTRACT FROM AUTHOR]

In this study, a commercially pure titanium (CP Ti) sheet was produced by the ARB process. Then, the mechanical properties of monolithic and nanocomposites specimens manufactured using 0.1, 0.3, and 0.5 wt% TiO 2 nanoparticles as the reinforcement were investigated at different ARB cycles. The results showed improvement in the mechanical properties of specimens with the addition of TiO 2 nanoparticles, as their yield strength and ultimate tensile strength were increased by increasing the TiO 2 nanoparticles percent. In this regard, the ultimate tensile strength of the monolithic specimen reached to 810 MPa, while it was 980 MPa, 1040 MPa, and 1085 MPa after applying 8 ARB cycles for 0.1 wt%, 0.3 wt% and 0.5 wt% nanocomposite specimens, respectively. However, the ultimate tensile strength of the as-received CP Ti sheet was 285 MPa. Moreover, the yield strength and the ultimate tensile strength were increased by increasing the number of ARB cycles and the total elongation; on the other hand, in the monolithic and nanocomposite specimens, it was decreased by increasing the number of ARB cycles. Grain refinements due to severe strain, work hardening and TiO 2 nanoparticles reinforcements were the main causes accounting for the improved mechanical properties. Recovery and dynamic recrystallization were two phenomena observed via TEM studies in the ARB process, leading to the development of equiaxed grains in the final ARB cycles. [ABSTRACT FROM AUTHOR]

In the present work, fatigue and cyclic deformation behavior of ultrafine-grained (UFG) pure aluminum AA1100 product by accumulative roll bonding (ARB) process under stress-controlled in the presence of mean stress were performed. After seven cycles of the ARB process, grain refinement due to severe strain imposed improves tensile properties. The fatigue life shows a substantial reliance on the ARB cycle, so that the fatigue life improves with the increasing ARB cycle. Fatigue-induced microstructural evolution was investigated by TEM microscopy. Cyclic deformation behavior in the presence of mean stress leads to strain accumulation in each cycle. The amount of strain accumulated increases by increasing mean stress and stress amplitude. TEM observations demonstrated that dense dislocation patterns such as dislocation tangle and LAGBs were recovered and turned into HAGBs during cyclic deformation. Low cycle fatigue-induced microstructural evolution. (a) after7 cycles of the ARB. process(initial specimen for fatigue test), (b) the formation of dislocation tangle and subgrain boundaries(after 60 cycles of fatigue test), (c) migration dislocations to grain. boundaries, and the formation of dislocation pile-up(during steady-state region after 300. cycles) (d) annihilation of dislocation within the grains and decreasing dislocation density. in grain interior(after failure). [Display omitted] • Fatigue and ratcheting behavior of nanostructured Al producted by the ARB process was investigated. • The amount of strain accumulation during cyclic deformation was investigated. • By increasing fatigue cycle, the amount of ratcheting strain was increased. • Microstructural evolution of Al-ARBed after 7 cycles was observed by TEM during cyclic deformation. • Mechanism of microstructural evolution during cyclic deformation was proposed. [ABSTRACT FROM AUTHOR]

In this work laminated metal composites with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by ARB. In order to vary the layer thickness and the number of interfaces different numbers of ARB cycles (4, 8 and 12) were applied. Subsequently, fatigue tests were performed and the related deformation and damage mechanisms were investigated. At high amplitudes crack growth occurs very straight through the whole sheet and is more or less unaffected by the interfaces of the individual layers in the composite. At lower amplitudes, where pronounced grain coarsening of the AA1050A layers occurs, the cracks deflect in front of the AA5005 layers and propagate in the coarsened AA1050A layers parallel to the bonding plane and the loading direction. Contrary to the composite, in both conventionally ARB processed AA1050A and AA5005 mono-material sheets grains are only locally coarsened around the crack tip and the fatigue cracks propagate very straight through the sheet width. Compared to AA1050A mono-material ARB sheets fatigue life and the cyclic stability are clearly enhanced in all composites. [ABSTRACT FROM AUTHOR]

Commercial pure Al sheets were severe plastically deformed at room temperature by accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB). Change in strain path was imposed during CARB by rotating the sheets with 90° around the normal direction axis between each cycle. Microstructural evolution of processed sheets was studied by electron back scattered diffraction (EBSD) analysis and revealed that nano/ultrafine grains (NG/UFG) with the average grain size of 380 nm and 155 nm were formed by both processing routes after eight cycles, respectively. The fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the CARB were 49% and 40.20°, respectively, in comparison to that of ARB sample (41% and 37.37°). Deformation texture evolution demonstrated that the change in strain path leads to the formation of strong orientation along the β-fiber. The major texture components for ARB specimens were Brass {011}<211> and S {123}<634> while those for CARB were Brass {011}<211> and Goss {011}<100>. The CARB processed specimen exhibited the tensile strength, microhardness and elongation of about 230 MPa, 92 HV and 13% compared with ARB sample (180 MPa, 80 HV and 10.5%) after eight cycles. Scanning electron microscopy (SEM) observations of tensile fracture surface of specimens revealed ductile type fracture. [ABSTRACT FROM AUTHOR]

In this paper, microstructure and mechanical properties of nano/ultrafine-grained (UFG) austenitic Fe-24Ni-0.3C steel fabricated by accumulative roll bonding (ARB) and subsequent annealing were studied. The results indicated that after 6 cycles of the ARB process, elongated UFG austenite with mean grain size of about 300 nm was obtained. Annealing treatment of 6-cycle ARB processed austenite at temperatures between 773 and 873 K resulted in formation of partly and fully recrystallized austenites with mean grain sizes between 750 nm to 2.5 μm. Discontinuous yielding accommodated with Lüders band deformation was observed in the stress-strain curves of the ARB processed specimens. Microstructural observation indicated that the Lüders band propagation corresponding to the propagation of the region where deformation-induced martensitic transformation occurred. It was found that deformation-induced martensitic transformation provided extra strain hardening ability, resulting in significant enhancement of uniform elongation in UFG metastable austenitic steel having ultrahigh strength and considerable uniform elongation. [ABSTRACT FROM AUTHOR]

This investigation aims to understand the differences in the recrystallization and grain growth textures in aluminum layers along the thickness direction of two layered composite sheets. The sheets were processed by five cycle accumulative roll bonding of commercially pure aluminum and an aluminum alloy containing 0.3 wt.% Sc both in the supersaturated solid solution and artificially aged conditions. Electron back scattered diffraction and transmission electron microscopy were used to characterize the microstructure and crystallography of the rolled and annealed composites. During the early stages of annealing the β-fiber rolling textures remain unchanged and becomes sustained by the so-called continuous recrystallization process. Then, at the completion of primary recrystallization in the later stages of annealing, orientation selective recrystallization occurs and the Brass orientation becomes eliminated. A strong β-fiber primary recrystallization texture was found to be favorable for the secondary recrystallization growth of Cube orientations. Otherwise, conventional grain growth occurs when the primary recrystallization textures have distortions in the β-fiber. [ABSTRACT FROM AUTHOR]

Nano/ultrafine grained (NG/UFG) AA2024 alloy produced by accumulative roll bonding (ARB) showed high strength (420 MPa) and very limited elongation (about 1.3%). A new strategy via ARB was developed to improve elongation (about 10%) of AA2024 alloy with a relatively high strength (365 MPa). The present strategy produced a bimodal structure consisting of coarse and ultrafine elongated grains in comparison to the UFG alloy. Electron backscattered diffraction (EBSD) revealed that after 4 ARB cycles, the fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the bimodal grain structure were 61% and 27.34°, respectively, in comparison to that of annealed (54% and 24.96°) and UFG (79% and 34.27°) alloy. The crystallographic texture results indicated that, unlike the annealed AA2024 alloy, the intensity of Brass {011}<211> and S {123}<634> components remarkably increased in the UFG and bimodal alloy. Scanning electron microscopy (SEM) observations demonstrated that failure mode in bimodal alloy was ductile fracture with a combination of deep and shallow dimples. [ABSTRACT FROM AUTHOR]

In this study, Al/WO 3 /SiC hybrid nanocomposite was produced using Al 1050 sheets and WO 3 and SiC nanoparticles through accumulative roll bonding (ARB) process. Uniaxial tensile test and hardness measurement were carried out on ARBed specimens. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) was used for microstructural observation. The results revealed that by increasing the number of ARB cycles, a better distribution of WO 3 and SiC nanoparticles was obtained in the Al matrix. So, after the 9th cycle, the hybrid nanocomposite showed an excellent distribution of the nanoparticles with strong bonding between the nanoparticles and the aluminum matrix. It has been shown that after 9 cycles, the microstructure exhibits a uniform of ultrafine grains elongated in rolling direction with an average grain size of approximate 400 nm. Furthermore, the tensile strengths of the hybrid nanocomposite enhanced by increasing the number of ARB cycle and reached to a maximum value of 204.5Mpa at the end of 9th cycle, which was 4.02 higher than that of the starting material. Also, the microhardness results suggested that with increasing the number of cycles, hardness increased rapidly at first stages and then dwindled at the last stages. [ABSTRACT FROM AUTHOR]

For the first time, the cross accumulative roll bonding (CARB) process was used as an effective alternative method for manufacturing Al/B 4 C/SiC hybrid composite strips and compared with the accumulative roll bonding (ARB) processed hybrid composite. The XRD results showed that nanostructured Al/B 4 C/SiC hybrid composites have successfully been fabricated by using CARB process without any additional phase. During CARB, the ceramic reinforcement particles (B 4 C and SiC) were more uniformly dispersed within the matrix compared with ARB process, due to changes in strain path. In addition, the tensile strength, elongation, and microhardness of CARB composites were measured to be higher than those in the ARB product. Finally, scanning electron microscopy (SEM) observations of fractured surfaces showed that fracture mode both hybrid composites was shear ductile rupture, dimples, and shear zones. [ABSTRACT FROM AUTHOR]

Cu-26Zn-5Al shape memory alloy (SMA) was produced by accumulative roll bonding (ARB) and subsequent heat treatment. In this regard, different austenitization cycles and cooling conditions, including furnace, air, cold-water, and boiling-water cooling were experimented. The heat-treated specimens were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The corrosion behavior of the specimens was also studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl solution. The results revealed that only by cooling in the boiling- and ice-water environments, a fully martensitic microstructure showing the shape memory effect is obtained. In contrast, by using the other cooling conditions, different phases like α-phase (Cu-saturated solid solution) are formed as well as martensite. From the corrosion testing results, it was found that the SMA specimens with the fully martensitic microstructure have the highest corrosion resistance, where cooling in boiling water was recognized to be optimal. In conclusion, Cu-26Zn-5Al SMA with an improved corrosion resistance can be produced by ARB followed by controlled heat treatment. • Cu-26Zn-5Al shape memory alloy (SMA) was successfully fabricated by ARB and heat treatment. • Cooling in boiling water was optimal to obtain Cu-Zn-Al SMA with improved corrosion resistance. • The contribution of grain size and galvanic couples was critical to the corrosion behavior of Cu-Zn-Al SMA. [ABSTRACT FROM AUTHOR]

In this study, multi-layered Al/Al–12%Si composites were produced by the accumulative roll bonding (ARB) at ambient temperature using commercial pure Al 1050 and Al–12%Si alloy sheets. The microstructures of Al and Al–12%Si alloy layers were characterized by scanning electron microscopy (SEM). Vickers microhardness and tensile tests were conducted to investigate mechanical properties of the composites. It was observed that by increasing ARB cycles, thickness of individual Al and Al–12%Si alloy sheets decreased; finally, Al–12%Si layers were necked at the second cycle. After the second ARB cycle, a multi-layered Al/Al–12%Si composite with homogeneously distributed Al–12%Si layers in aluminum matrix was produced. Si phase was refined from 65.6 to 25.57 µm in length and the Al grain size was reduced from 25 to 7.2 μm. The formation of Al 3.21 Si 0.47 intermetallic phase after the second cycles was confirmed by X-ray diffraction. The results showed that the tensile strength increased up to 270 MPa after first cycle and dropped afterwards. Microhardness measurement indicated that hardness of individual layers increased continuously with increasing the ARB cycles. [ABSTRACT FROM AUTHOR]

The accumulative roll bonding process is one of the most prominent severe plastic deformation processes for obtaining sheet materials with ultra-fine-grained microstructures and high strength. The properties of such sheets differ significantly from those of conventionally rolled sheets. It is hence desirable to have a simulation framework that can accurately predict the material properties, including the evolving texture and anisotropy during processing. Here, we propose such a framework for multiple pass rolling using explicit finite elements and embedding the visco-plastic self-consistent (VPSC) polycrystal texture model for the material response. To facilitate multiple pass rolling, we propose a novel solution mapping scheme that transfers the material state from the deformed finite element mesh to a new one. Additionally, we implement a two-level parallelization scheme – with decomposition of the FE domain using message passing interface (MPI) and thread based parallelization of the material response using openMP – to ensure reduced simulation times. The predictive capabilities of the proposed framework are demonstrated by simulating the accumulative roll bonding of aluminum alloy AA5754 sheets. The simulations validate the working of the solution mapping scheme, and clearly show the development of a through thickness gradient of texture and anisotropy in the roll-bonded sheet after two passes. [ABSTRACT FROM AUTHOR]

Accumulative roll bonding (ARB) was used to fabricate aluminum matrix composites (AMCs) with 2 vol% Al 2 O 3 particles. Monolithic sheets without Al 2 O 3 particles under the same conditions were also fabricated for comparison. For all produced sheets, different variables, such as average grain size, fraction of high angle grain boundaries and local number of 2-dimension at random points (LN2DR), were measured to better understand the evolution of matrix microstructure and particle spatial distribution. The role of Al 2 O 3 particles on strengthening in AMCs processed by ARB was finally revealed. It was found that during ARB, monolithic sheets exhibited deformed-micrometer grains. In comparison, composites also started with deformed-micrometer grains, however, evolved over ARB cycles to have significantly refined grains. Machine learning results showed that particle spatial uniformity improved with the increasing number of ARB cycles. After the 11 cycles of ARB, final composites were more strengthened (1.15 times higher Vickers hardness, 1.19 times higher tensile strength), however, had less elongation than the monolithic sheets. Therefore, comparing to monolithic sheets, the composites are more strengthened not only due to the matrix strain hardening and grain refinement caused by ARB, but also the presence of Al 2 O 3 particles with improved spatial uniformity. • Composite aluminum sheets were produced by accumulative roll bonding (ARB). • Aluminum matrix in composite sheets evolved during ARB to have ultrafine grains. • Particle uniformity improves with increasing ARB cycles, shown by machine learning. • Composites were more strengthened compared to monolithic sheets. • The composite rupture mode is brittle, but elongation slightly improved during ARB. [ABSTRACT FROM AUTHOR]

• First study using machine learning on accumulative roll bond (ARB) processed composites. • Repeated ARB cycles promote decohesion and uniformity of reinforcement particles and refine matrix grains. • Composite microstructure evolves and consequently, tensile properties improve. • All composite parameters saturate from 14 cycles, suggesting limitation of ARB in strengthening. The effects of repeated accumulative roll bonding (ARB) cycles on reinforcement phase features, matrix microstructure and composite tensile behavior evolution were investigated by microscopy, machine learning, tensile testing, and fracture surface observation. The results showed that with increasing ARB cycles, the reinforcement particles decohered and their distribution uniformity improved. Meanwhile, the matrix microstructure evolved and consequently, the mechanical properties of the composite were improved. However, all parameters saturated at higher ARB cycles suggesting the limitation of further cycles in strengthening composites. These findings are significant for enhancing the knowledge about the microstructure and mechanical properties of particle reinforced composite and optimizing the fabrication of composites by ARB. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructuring of titanium-based implantable devices can provide them with superior mechanical properties and enhanced biocompatibity. An overview of advanced fabrication technologies of nanostructured, high strength, biocompatible Ti and shape memory Ni–Ti alloy for medical implants is given. Computational methods of nanostructure properties simulation and various approaches to the computational, “virtual” testing and numerical optimization of these materials are discussed. Applications of atomistic methods, continuum micromechanics and crystal plasticity as well as analytical models to the analysis of the reserves of the improvement of materials for medical implants are demonstrated. Examples of successful development of a nanomaterial-based medical implants are presented. [Copyright &y& Elsevier]

Abstract: The evolution of the new microstructures produced by two types of dynamic recrystallization is reviewed, including those brought about by severe plastic deformation (SPD). The microstructural changes taking place under these conditions and the associated mechanical behaviors are described. During the conventional discontinuous dynamic recrystallization (dDRX) that takes place at elevated temperatures, the new grains evolve by nucleation and growth in materials with low to medium stacking fault energies (SFE). On the other hand, new ultrafine grains can be produced in any material irrespective of the SFE by means of SPD at relatively low temperatures. These result from the gradual transformation of the dislocation sub-boundaries produced at low strains into ultrafine grains with high angle boundaries at large strains. This process, termed in situ or continuous dynamic recrystallization (cDRX), is still not perfectly understood. This is because many SPD methods provide data concerning the microstructural changes that take place but little information regarding the flow stress behavior. By contrast, multi-directional forging (MDF) provides both types of data concurrently. Recent studies of the deformation behavior of metals and alloys under SPD conditions, carried out using MDF as well as other SPD methods, are synthesized and the links between the microstructural and mechanical observations are examined carefully. Some models for grain formation under SPD conditions are discussed. Next, the post-dynamic recrystallization behavior, i.e. that of annealing after both dDRX and cDRX, is described. The differing annealing behaviors result from the differences in the natures of the deformed microstructures. Finally, an integrated recrystallization model for these phenomena, i.e. dynamic and static recrystallization of both the continuous and discontinuous types, is presented and discussed. [Copyright &y& Elsevier]

Abstract: A transmission-electron-microscope-based orientation mapping technique that makes use of beam precession to achieve near-kinematical conditions was used to map the phase and crystal orientations in nanolamellar Cu/Nb composites with average layer thicknesses of 86, 30 and 18nm. Maps of high quality and reliability were obtained by comparing the recorded diffraction patterns with pre-calculated templates. Particular care was taken in optimizing the dewarping parameters and in calibrating the frames of reference. Layers with thicknesses as low as 4nm were successfully mapped. Heterophase interface plane and character distributions (HIPD and HICD, respectively) of Cu and Nb phases from the samples were determined from the orientation maps. In addition, local orientation relation stereograms of the Cu/Nb interfaces were calculated, and these revealed the detailed layer-to-layer texture information. The results are in agreement with previously reported neutron-diffraction-based and precession-electron-diffraction-based measurements on an accumulated roll bonding (ARB)-fabricated Cu/Nb sample with an average layer thickness of 30nm as well as scanning-electron-microscope-based electron backscattered diffraction HIPD/HICD plots of ARB-fabricated Cu/Nb samples with layer thicknesses between 200 and 600nm. [Copyright &y& Elsevier]

Highlights: [•] Al/Al2O3/SiC hybrid composite was fabricated by anodizing and ARB processes. [•] With no. of ARB cycles, the uniformity of particles in the Al matrix improved. [•] With no. of ARB cycles, the bonding quality between particles and matrix improved. [•] The UTS of Al/1.6vol.% Al2O3/1vol.% SiC was 3.1 times higher than annealed Al. [•] Increasing the amount of the SiC up to 2vol.% in matrix decreased UTS and El%. [ABSTRACT FROM AUTHOR]

Multilayer Zn–Al eutectoid alloy (ZA22) was fabricated via accumulative roll bonding (ARB) for the first time, and the microstructural evolution, damping and tensile mechanical properties of the resultant specimens were studied. In the early stage of ARB, Zn–Al alloy layers were firstly formed between Zn and Al layers. With increasing the cycles of ARB, the volume fraction of the alloy layers increased gradually. After 9 cycles of ARB, the ZA22 alloy with uniform composition was obtained. Property tests showed that after 6 cycles of ARB, the damping in a wide temperature range from room temperature to around 275 °C, the tensile strength and the elongation to failure began to be higher than those of the cast ZA22 alloy. In particular, the elongation to failure of the ARB-7 specimen was 10.7 times that of the cast ZA22 alloy. Solution treatment could further significantly improve the damping and the elongation to failure. The microstructural origins of the improved properties were discussed in detail. • Multilayer ZA22 alloy was successfully fabricated via ARB for the first time. • Resultant specimens have significantly improved damping and mechanical properties. • The elongation of the ARB-7 specimen is 10.7 times that of the cast ZA22 alloy. • Solution treatment can further dramatically improve the damping and elongation. • Microstructural origins of the improved properties were discussed in detail. [ABSTRACT FROM AUTHOR]

Highlights: [•] Because of the ARB process, the general corrosion resistance decreases. [•] With increasing the number of ARB cycle, the corrosion resistance slightly increases. [•] The corrosion resistance of the nanocomposites increases in the lower cycles. [Copyright &y& Elsevier]

Abstract: Pure Cu, Cu–0.41at.% Si and Cu–1.64at.% Si alloys were severely deformed by an accumulative roll bonding (ARB) method and the resultant microstructure was observed using high-voltage electron microscopy and scanning transmission electron microscopy. Although the mean boundary separation along the ARB normal direction was dependent on the Si concentration, the dislocation density within grains and cells depended very weakly on the Si concentration and stayed around 5×1014 m−2. Uniaxial tensile tests were also performed at room temperature. The contribution of dislocations and grain boundaries to the strength was estimated using two models: one based on the Taylor-type and Hall–Petch-type strengthening mechanisms, the other based on thermally activated dislocation depinning from grain boundaries. Both model provide reasonable values for yield strength compared with 0.2% proof stress values, and therefore the grain size region used in this study may be the transition region between these two models. [Copyright &y& Elsevier]

The miniaturized Erichsen test was successfully developed for evaluating the stretch formability of the ARB and annealed IF steel sheets. The Erichsen value tends to decrease as the average grain size becomes small. However, it should be emphasized that even in the specimen with ultrafine grain, a high Erichsen value is obtained. This result indicates that the ultrafine grained IF steel sheet could be highly deformed under multiaxial stress. [ABSTRACT FROM AUTHOR]

The dynamic tensile deformation behavior of ultrafine-grained interstitial free steel is shown in this paper. As the strain rate increased, the yield drop phenomenon became more significant in the stress–strain curves. The difference in flow stress between the dynamic and quasi-static strain rates did not decrease with grain refinement, in contrast to conventional high-strength steels. It is suggested that the grain refinement affected mainly the athermal component of the flow stress. [ABSTRACT FROM AUTHOR]

Abstract: The strength of a biomedical -type alloy, Ti–25Nb–3Zr–3Mo–2Sn, was enhanced through severe plastic deformation using a modified accumulative roll bonding technique. Incremental strength increases were observed after each cycle, while ductility initially fell but showed some recovery with further cycles. After 4 cycles there was a 70% improvement in the ultimate tensile strength to 1220 MPa, a two-fold increase in the 0.5% proof stress to 946 MPa and the ductility was 4.5%. The microstructure comprised of ultrafine grain grains heavily elongated in the rolling direction with a fine dispersion of nanocrystalline phase precipitates on the grain boundaries. Shear bands formed in order to accommodate large plastic strains during processing and the grains within the bands were significantly finer than the surrounding matrix. [Copyright &y& Elsevier]

Ceramic nanoparticles produced by comminution are introduced homogeneously during accumulative roll bonding (ARB) in aluminium AA1050A by airgun spraying from a stabilized aqueous suspension. In the so-produced nanoparticle-reinforced ultrafine-grained material, acceleration of microstructural evolution during the early ARB cycles as well as reduced grain sizes at higher cycles are observed, both caused by additional local straining around the embedded nanoparticles and accompanied by further strengthening. The presented method of nanoparticle application allows homogeneous as well as graded particle distribution. [ABSTRACT FROM AUTHOR]

Abstract: Wear behavior of severely deformed aluminum sheets by accumulative roll bonding (ARB) process was characterized using a pin on disc wear machine at different conditions. The sheets were processed up to eight ARB cycles in order to induce a high strain (~6.4) to the samples. EBSD results showed that after eight cycles of ARB, sheets were found to contain ultrafine grains with high fraction of high angle grain boundaries. Wear experiments were conducted under different loading and operating conditions, including dry and immersion lubrication, and rotation speeds. Wear was continuously monitored by measuring the wear rates and morphologies of worn surfaces by scanning electron microscope (SEM). Contrary to expectation, the wear resistance of the ARBed Al sheets was less than the non-processed sheets. Wear rates of the ARBed Al sheets increased by increasing wear load and rotation speed, while, immersion lubrication decreased the wear rate significantly. Based on the observation and results, a model for the wear of the ARBed Al was proposed. [ABSTRACT FROM AUTHOR]

Abstract: Dislocation density within ultrafine grains in severely deformed aluminium was evaluated by the scanning transmission electron microscopy. The values were around 1014 m−2 in commercial pure aluminium samples with equivalent strain up to 10. The obtained dislocation densities values correspond to strength between 55MPa and 70MPa according to the Bailey–Hirsch relationship. [Copyright &y& Elsevier]

Abstract: The plastic anisotropy of ultrafine grained aluminium alloys AA1050 and AA6016 produced by accumulative roll bonding (ARB) has been investigated by tensile deformation via the Lankford parameter. The average normal and planar anisotropies slightly increase (from 0.6 to 0.9) and decrease (from 0.6 to −0.7) as a function of ARB cycles, respectively. The global textures measured by neutron diffraction are used to simulate the Lankford and anisotropy parameters of the plates after 0, 2, 4, 6 and 8 ARB cycles with the help of the viscoplastic polycrystal self-consistent model. Simulation results are compared with those from experiment and discussed with regard to texture, strain rate sensitivity, grain shape and slip system activity. [Copyright &y& Elsevier]

Positron annihilation spectroscopy was performed in order to study the influence of preparation route and processing on atomic free volumes in amorphous and nanocrystalline aluminium alloys. In melt-spun amorphous Al88Y7Fe5, structural free volumes smaller than a lattice vacancy are predominant, whereas in amorphous Al92Sm8 prepared by repeated cold rolling larger free volumes occur. In the early stages of nanocrystallization of Al88Y7Fe5, an indication of Y enrichment at interfacial free volumes in the growth front of the Al nanocrystallites is found. [Copyright &y& Elsevier]

Abstract: In the present study, a new manufacturing process for Al–SiCP composites was developed by using bulk aluminum sheets and micron sized SiC particles as starting materials. Nanostructured Al–SiCP composites with average grain size of 180nm were successfully produced in the form of sheets, through accumulative roll bonding (ARB), at room temperature. To evaluate microstructure of the produced composites, scanning electron microscope (SEM) and transmission electron microscope (TEM) were applied. The microstructure of the fabricated composites revealed properly distributed SiC particles in the aluminum matrix. Mechanical properties of the Al–SiCP composites were investigated by the tensile test. The results proved that by increasing ARB cycles the tensile strength of the produced composites increases, but their ductility at first decreases and then increases. [Copyright &y& Elsevier]

Abstract: Ultrafine-grained sheets of the commercial-purity aluminium AA1050 and the aluminium alloy AA6016 were processed by accumulative roll bonding. As-received, conventionally grained and ultrafine-grained aluminium sheets with an average grain size ranging from 20μm to 30μm and 200nm, respectively, were successfully joined by friction stir welding, and the microstructure and the mechanical properties of the welded zone were investigated. Ultrafine-grained materials showed softening in the nugget, although the hardness remained comparable to the as-received, conventionally grained aluminium sheets. [Copyright &y& Elsevier]

The heavy-ion irradiation behavior of bulk zirconium-niobium multilayered composites was investigated up to large doses. Multilayers with an average individual layer thicknesses ranging between 15 and 80 nm were synthesized by accumulative roll bonding technique. The irradiation was performed with a defocused 7 MeV Zr2+ ion beam at 500 °C. The maximum dose achieved was ∼145 dpa at the depth of ∼1.5 μm from the irradiated surface. Sub-surface microstructural damage and the chemical redistribution were characterized by transmission electron microscopy and energy dispersive spectroscopy, respectively. Irrespective of the layer thicknesses, the irradiation condition caused layer instability and the extent of damage varied with the dose levels. Doses lesser than ∼60 dpa caused layer fragmentation and greater than ∼60 dpa resulted in layer dissolution. The chemical mixing of layers occur to a depth of ∼1 μm, consuming multiple bi-layer periods. Despite the elevated irradiation temperature (500 °C) and a slightly positive heat of mixing (+6 kJ/mol), no phase separation was observed and single-phase was retained in the mixed region. The results demonstrate that chemical mixing was facilitated by the liquid phase miscibility of Zr and Nb, which propelled the interdiffusion within the thermal spikes towards mixing. [ABSTRACT FROM AUTHOR]

Abstract: High-purity aluminum (99.99% purity) deformed by accumulative roll bonding to an equivalent strain of 4.8 has been characterized by transmission electron microscopy and electron backscatter diffraction techniques in the deformed state and after various annealing treatments. These two techniques are compared and discussed. The majority of the structure in the as-deformed state is composed of equiaxed crystallites surrounded mostly by high-angle boundaries with misorientation angle above 15°. However, regions that contain a high concentration of low-angle boundaries with misorientation angle below 15° in a lamellar structure elongated along the rolling direction have also been observed. The microstructure is correlated with the local texture as the equiaxed structure contains a mixture of texture components whereas the lamellar structure has orientations corresponding to rolling or shear texture components. Annealing of deformed specimens causes structural coarsening without removing the regions with a high concentration of low-angle boundaries. Heat treatment for a short period of time (0.5h) leads to the start of recrystallization at 200°C, whereas a heat treatment at 175°C for an extended period (6h) allows heat treatments to be carried out at temperatures above 200°C without initiation of recrystallization. The two-step process is a promising route for producing almost uniform equiaxed structures by annealing of samples that have been deformed to large strains. [Copyright &y& Elsevier]