Accumulative Roll Research Articles

Excellent mechanical properties and strengthening mechanisms in ultrathin foils of CoCrNi medium-entropy alloy via accumulative rolling

Ultrathin foils are used in multiple fields, including aerospace, and precision instrument design. In this paper, CoCrNi medium-entropy alloy (MEA) ultrathin foils with terminal thicknesses of 77 μm were prepared by accumulative cold rolling at room temperature. The quasi-static tensile properties of the rolled ultrathin foils were tested. The influence of the reduction ratio and thickness values on their mechanical properties was studied through EBSD and TEM. The results showed that the CoCrNi MEA ultrathin foils exhibited excellent tensile performance when the thickness reached 160 μm, in which the tensile strength reached 1.69 GPa at a tensile elongation of 7 %. Microstructure characterization revealed that the dominant strengthening mechanism of the CoCrNi ultrathin foils were composed of grain boundary and dislocation strengthening. Specifically, when the thickness exceeded 160 μm, enhanced dislocation and grain size strengthening cause ' work hardening ', and the strength gradually increased with decreasing thickness. When the thickness was 160 μm, the strengthening effect produced by dislocation banding, twinning, and multistage twinning delivery significantly influenced the mechanical properties of the foils. When the thickness was less than 160 μm, this process mainly occurred due to the interactions of dislocation proliferation and annihilation in the grain, causing the strength to decrease gradually with decreasing thickness, thereby resulting in ' work softening '.

Magnesium based multi-metallic hybrids with soot for hydrogen storage

Magnesium hydride is one of the most sought-after materials for solid state hydrogen storage due to its low cost and high gravimetric capacity (7.6 wt% hydrogen). However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties. It is seen that the hybrid absorbs ∼6.2 wt% hydrogen at a plateau pressure of ∼2 bar at 300 °C and exhibits fast kinetics with ∼6.6 wt% hydrogen absorption within ∼30 min at 300 °C and 20 bar hydrogen pressure. The role of Mg2Ni as a catalyst as well as hydrogen absorbing medium provides an effect akin to ‘hydrogen pump’, thus enhancing the rate of hydrogen absorption. Presence of carbon in various forms such as aciniform, carbonaceous microgel and cenospheres (derived from soot) plays a vital role by providing channels for diffusion of hydrogen through the hybrid. The ARB technique provides an inexpensive and scalable method of synthesis of Mg based hybrids with large number of interfaces and high amount of strain leading to enhanced hydrogen storage properties.

Preparation, Microstructure, and Mechanical Properties of Aluminum Matrix Composite by Accumulating Roll Bonding Method

The ARB (Accumulative Roll Bonding) method is greatly watched as a new severe plastic deformation process that uses only a conventional general rolling machine. The ARB method is a preparation method of ultra-fine-grained, high-strength thin metal and alloy sheets by repeated rolling. The purpose of this study was to clarify the effectiveness of the ARB method as a metal matrix composite manufacturing process. At first, alumina particles and short carbon fibers were used as dispersoids, and pure aluminum was used as the thin plate. Then, the dispersoids were deposited on a pure aluminum plate to 2 vol.% dispersoids. Six of these aluminum sheets were stacked to form a multi-layer composite sheet, which was then cold rolled at a rolling reduction of 67%. After rolling, the sheet composites were cut in half, overlapped, and rolled again. The composites were obtained by repeating this process. When the repetition exceeded 6 times, the dispersoids tended to disperse in the aluminum matrix. In addition, uniform dispersion progressed through further repeat rolling. By repeated rolling, the tensile strength of the composite sheets was greatly improved. In addition, the tensile strength of the composites was higher than that of the ARB-processed monolithic aluminum sheet. The improvement in strength was caused by the refinement of aluminum grains rather than the particle dispersion.

Accumulative roll bonding of aluminum alloy 6082: Microstructural evolution and mechanical properties

AbstractMaterial strengthening is a key objective of researchers and scientists in the present scenario for industrial applications. Although many processes can strengthen and refine grains, severe plastic deformation is the most dominant of all other techniques. Accumulative roll bonding is one of the severe plastic deformation techniques. This study examined how the various accumulative roll bonding cycles at the elevated preheating temperature affected the mechanical characteristics and microstructural evolution of the AA6082 strip. An optical microscope, scanning electron microscope, and electron backscatter diffraction were used to analyze the bonding and microstructural features. To determine mechanical characteristics, tensile and microhardness tests were also performed. The ultrafine grain size was achieved after accumulative roll bonding processing of AA6082. Accumulative roll bonding processing enhances mechanical properties like tensile strength and microhardness during the initial accumulative roll bonding cycle, but these properties grow more slowly at higher accumulative roll bonding cycles. However, the elongation value considerably decreased in the first cycle before stabilizing. The nice bonding between the layers was seen after accumulative roll bonding. Even after accumulative roll bonding, the fracture morphology reveals a ductile mode of fracture.

Mechanical properties, corrosion behavior, and cytotoxicity of biodegradable Zn/Mg multilayered composites prepared by accumulative roll bonding process

Zinc (Zn), magnesium (Mg), and their respective alloys have attracted great attention as biodegradable bone-implant materials due to their excellent biocompatibility and biodegradability. However, the poor mechanical strength of Zn alloys and the rapid degradation rate of Mg alloys limit their clinical application. The manufacture of Zn and Mg bimetals may be a promising way to improve their mechanical and degradation properties. Here we report on Zn/Mg multilayered composites prepared via an accumulative roll bonding (ARB) process. With an increase in the number of ARB cycles, the thicknesses of the Zn layer and the Mg layer were reduced, while a large number of heterogeneous interfaces were introduced into the Zn/Mg multilayered composites. The composite samples after 14 ARB cycles showed the highest yield strength of 411±3 MPa and highest ultimate tensile strength of 501±3 MPa among all the ARB processed samples, significantly higher than those of the Zn/Zn and Mg/Mg multilayered samples. The Zn and Mg layers remained continuous in the Zn/Mg composite samples after annealing at 150 °C for 10 min, resulting in a decrease in yield strength from 411±3 MPa to 349±3 MPa but an increase in elongation from 8±1% to 28±1%. The degradation rate of the Zn/Mg multilayered composite samples in Hanks’ solution was ranged from 127±18 µm/y to 6±1 µm/y. The Zn/Mg multilayered composites showed over 100% cell viability with their 25% and 12.5% extracts in relation to MG-63 cells after culturing for 3 d, indicating excellent cytocompatibility. Statement of significanceThis work reports a biodegradable Zn/Mg multilayered composite prepared by accumulative roll bonding (ARB) process. The yield and ultimate tensile strength of the Zn/Mg multilayered composites were improved due to grain refinement and the introduction of a large number of heterogeneous interfaces. The composite samples after 14 ARB cycles showed the highest yield strength of 411±3 MPa and highest ultimate tensile strength of 501±3 MPa among all the ARB processed samples. The degradation rate of the Zn/Mg multilayered composite meets the required degradation rate for biodegradable bone-implant materials. The results demonstrated that it is a very promising approach to improve the strength and biocompatibility of biodegradable Zn-based alloys.

In situ observation of destabilization of a nanostructured Ag/Cu multilayer fabricated via multicomponent accumulative roll bonding

Nanostructured metallic multilayered composites have many excellent properties due to their high-density heterophase interfaces, but they also pose challenges to the thermal stability of their multilayered structures. In this work, destabilization behavior of nanostructured Ag/Cu multilayer with an individual layer thickness of 40 nm prepared by multicomponent accumulative roll bonding is directly observed by transmission electron microscope. The results show that the destabilization of the nanostructured Ag/Cu multilayer originates from the interfacial instability perturbation driven by compositional gradient and capillary force. The subsequent destabilizing process is closely related to the cross-sectional ratio of the lamellar structure. When the thickness difference between adjacent lamellae is large, the lamellae with smaller thickness will follow a destabilizing sequence of perturbation → necking → pinching → termination migration. While the thickness of adjacent lamellae is similar, the perturbed lamellae tend to form stable grooves during roughening.

Correction: Microstructure evolution and mechanical properties of the AA2024/AA5083 ultra-fine grained composite fabricated via accumulative roll bonding (ARB) method

Correction: Microstructure evolution and mechanical properties of the AA2024/AA5083 ultra-fine grained composite fabricated via accumulative roll bonding (ARB) method

Electrochemical corrosion of aluminium alloy AA1050, processed by accumulative roll bonding

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The effect of layer interface on recrystallization behavior of layered aluminum: An in-situ EBSD study

In recent years, layered heterogeneous metallic materials have received considerable attention. In this work, we fabricated an AA3003/AA1060 layered aluminum and introduced heterogeneity by regulating recrystallization behavior via accumulative roll bonding and annealing processes. The annealing process was studied by in-situ electron backscatter diffraction (EBSD) observation. The present work shows that the recrystallization rate in the AA1060 layer is significantly higher than that in the AA3003 layer. This disparity can be attributed to the varying element composition, which generates a layered aluminum structure comprising alternating fine-grained and coarse-grained layers. Moreover, the influence of layer interface on the recrystallization behavior of the AA1060 layer was investigated. The result shows that high energy storage near the interface promotes recrystallization nucleation and grain growth. This study reveals the formation mechanism of layered heterogeneous metallic materials, which can help the design and preparation of high-performance heterogeneous metallic materials.

Fabrication of Al/BN composite strips and evaluation of fracture toughness and forming limit diagram

In this study, mechanical properties, fracture toughness (FT) and forming limit diagram (FLD) of Al base composites manufactured by accumulative roll bonding (ARB) have been studies experimentally. AA1100/BN composite strips have been manufactured with thickness of 1 mm up to 10 ARB cycles at 300°C. Their strength enhanced to 168 MPa which was 248 % enhancement than the primary aluminum alloy 1100. Also, the bonding between layers enhanced by fabrication of thin layers through the thickness of composites with more plastic strains. SEM fracture morphology of composites showed that a shear ductile fracture was achieved at higher passes. So, relative to the annealed sample, deep dimples are shrinking slowly. UTS, elongation and hardness of samples improved to 169 MPa, 11.4 % and 55.6 HV after the 10 cycle, respectively. After the first pass as the criterion of formability, the area under the FLDs dropped sharply and then enhanced at higher passes. Based on the results obtained FT enhanced to 30 MPam12 at the 10th pass.

Investigation on Various Ceramic Nanoparticles Reinforced Aluminum Matrix Composites via Accumulative Roll Bonding and Cryorolling

Accumulative roll bonding (ARB) and cryorolling (CR) processes are used to fabricate three kinds of composites of AA1050 reinforced with SiCp and TiCp, to become the Al‐SiCp, Al‐TiCp, and Al‐SiCp‐TiCp composites. The effects of reinforced particles and different passes of ARB and CR on mechanical properties, microstructure, and particle distribution are studied. The microstructure shows the uniform distribution of particulates, decreased porosity, and excellent bonding between particle and matrix as the rolling cycles increased. Mechanical properties of the ARBed and cryorolled sheets are examined, and samples are compared with matrix alloy and composites. The findings demonstrate that the Al‐SiCp, Al‐TiCp, and Al‐SiCp‐TiCp composites improve the elastic modulus, yield strength, and hardness. After comparing the results of composites, the best combination of hardness, yield strength, ultimate tensile strength, toughness, and young modulus base composite has been chosen. Al‐TiCp and Al‐SiCp composites demonstrate ductile fracture behavior, as observed through SEM testing, while Al‐SiCp‐TiCp composite sample exhibits a bimodal fracture. This composite should aid in the creation of lightweight composites for use in aeronautical applications.

Creep mechanism in ductile dual-phase aluminum alloys with a fully continuous fiber state

To understand the creep behavior of a practical alloy that has a multiphase consisting of a matrix and several types of precipitate phases, the role of individual phases needs to be studied. However, it is difficult to elucidate the contribution of each phase to creep owing to their complex microstructural morphologies and very complex creep behavior. To understand the role of individual phases and the creep behavior, fundamental creep theories for ductile dual-phase (DDP) alloys must be established initially for specimens with simple microstructural morphologies. To apply these theories practically, they must also be experimentally verified. In this study, DDP alloys composed of 99.99 % Al (matrix phase) and an Al–Mg solid-solution alloy (reinforced phase) were fabricated as a fully continuous fiber state by accumulative roll bonding. Tensile and creep tests at elevated temperatures were performed on alloys composed of systematically varying volume fractions of the reinforced phase. Tensile data at 546 K indicated a linear relationship between the maximum stress and volume fraction of the reinforced phase; the lines were also connected to the data from single-phase materials of the matrix and reinforced phase. Thus, the amount of strain in the matrix and reinforced phases was the same as that during the tensile test, and the relationship between the maximum stress and volume fraction of a DDP alloy followed the classical linear law of mixtures (CLLM). The creep data for Al + Al–2Mg (DDP alloy) at 546 K were nearly equal to those calculated using the CLLM. Thus, the matrix and reinforced phases deformed at the same creep rate. Creep tests were also conducted for Al + Al-1M(5ARB), which had a fine-grained reinforced phase. The creep data for Al + Al-1M(5ARB) at 523 K were also a good approximation to the lines representing the data calculated using the CLLM. Hence, although the grain sizes of the two phases were very different, corresponding to different rate-controlling mechanisms, the creep data for a DDP alloy could be analyzed using the CLLM. Consequently, the creep behavior of the DDP alloys was a superposition of the creep behavior in both phases, and the interpretation of the creep data for DDP alloys using the creep theory of single-phase materials would lead to incorrect conclusions. These findings will contribute to a better understanding of the creep behaviors of practical alloys and will aid in the correct estimation of the creep lifetime.

Near-Surface Layer Perforations as Precursors to Fracture in Accumulative Roll Bonding of a Multilayered Metal Composite

Near-Surface Layer Perforations as Precursors to Fracture in Accumulative Roll Bonding of a Multilayered Metal Composite

A novel strategy for fabricating phase transforming NiTi shape memory alloy via multiple processes of severe plastic deformation

NiTi shape memory alloy was successfully fabricated from Ni/Ti multilayers via an innovatively combinative route consisting of accumulative roll bonding (ARB), high-pressure torsion (HPT) and annealing. Due to the severe plastic deformation induced by ARB and HPT, the subsequent post annealing time was significantly reduced. Differential scanning calorimetry (DSC) analysis confirms the occurrence of austenitic and martensitic transformations during heating and cooling process, implying that the shape memory effect was obtained.

Intelligent prediction model of mechanical properties of ultrathin niobium strips based on XGBoost ensemble learning algorithm

Ultrathin niobium strips with different thicknesses are prepared by an accumulative rolling process. The tensile test of the ultrathin niobium strips is carried out, and the microstructure of each niobium strip is characterized by electron backscattered diffraction (EBSD). The process parameters, mechanical properties and microstructure characterization data of rolled ultrathin niobium strips with different thicknesses are collected, analyzed and sorted. A data-driven intelligent prediction model for the mechanical properties of ultrathin niobium strips is established by deeply integrating the mechanical properties of ultrathin niobium strips with the microstructure evolution mechanism and combining the integrated data with the XGBoost ensemble learning algorithm. The optimal parameters of the XGBoost model are determined by a grid search and used for mechanical performance prediction. The overall generalization performance of the model is evaluated by the coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE) and mean absolute percentage error (MAPE). To reflect the advancement of the proposed model, the prediction results of this model are compared with those of the random forest (RF), multi-layer perceptron (MLP) and gradient boosting decision tree (GBDT) prediction model. The research results show that, on the test set, the R2 in terms of the tensile strength and yield strength predicted values based on the XGBoost algorithm were higher than those of other models, reaching 0.944 and 0.964, respectively. The three error indicators corresponding to the XGBoost model were also at the lowest level. This means that the model based on the XGBoost algorithm has the optimal generalization performance and can thus realize the accurate prediction of the mechanical properties of ultrathin niobium strips. This research provides a new method and idea for the optimal design of rolling process and the prediction of their mechanical properties.

Numerical and experimental investigations of mechanical, tribological, and electrical properties of laminated Bi-metal Al/SiC/Ni composites

Bimetal pure Al/SiC/Ninanocomposites are a remarkable class of nanocomposite materials with a layered structure comprising pure aluminum, silicon carbide nanoparticles, and nickel. The ingenious design of these nanocomposites aims to synergistically combine the desirable properties of each constituent material, resulting in an exceptional enhancement of mechanical, thermal, and electrical characteristics. This study focused on fabricating 1-mm bimetal pure Al/SiC/Ni nanocomposites using an accumulative roll bonding process. The rolling process was conducted for eight cycles at a controlled temperature of 250 °C. To understand the behavior of the bonding interface between the aluminum/nickel layers, a comprehensive investigation was carried out using finite element simulation techniques. The study specifically delved into the bonding mechanisms between the aluminum and nickel layers, employing simulation and experimental procedures. A series of rigorous tests were conducted to evaluate the resulting nanocomposites comprehensively. These included tensile strength tests, peeling tests, average Vickers micro hardness tests, wear-resistant tests, electrical resistance testing, and scanning electron microscopy analysis. These tests thoroughly examined the evolution of the microstructure and the nanocomposites’ mechanical properties. The obtained results conclusively demonstrate that the supplementary accumulative roll bonding process led to substantial improvements in the nanocomposites’ mechanical properties, wear resistance, and electrical resistance properties. Furthermore, the simulation results indicate that the optimal bonding conditions, characterized by robust interfacial bonding, were achieved at higher cumulative rolling cycles.

Texture evolution and hardening behavior of Al/IF composite produced through severe plastic deformation

In this research, the microstructure, texture, and work hardening behavior of the Al/IF composite were investigated. The composites were produced through up to 7 cycles of accumulative roll bonding (ARB). The microstructure evolution revealed that the IF layer fractured during the process and distributed within the Al matrix due to its higher hardness and higher work hardening rate, as well as formation of shear bands. The main deformation textures formed in the Al layer were the {001} <110>, {4,4,11} <11,11,8>, and {111} <112> components. In the IF layer, preferred orientations of {001} <110>, {110} <112>, and {111} <110> were observed. The produced composite exhibited typical tensile behavior, with strength increasing and elongation decreasing during the process due to an increment in dislocation density and hardening. Additionally, the results revealed that the hardening capacity of the composite decreased during the process; however, the strain hardening rate increased. A noticeable increase in dislocation density and a decrease in crystallite size were found to be the main governing parameters of these variations. Moreover, the fracture mode of the composite changed from ductile fracture to a more brittle mode as a result of hardening.

ELECTROMAGNETIC PROPERTIES, FORMING LIMIT DIAGRAMS AND FRACTURE TOUGHNESS OF LAMINATED Al/Fe2O3 COMPOSITES

In this study, electrophysical, electromagnetic and mechanical properties, fracture toughness and forming limit diagram (FLD) of Al base composite samples have been studied experimentally. All samples have been fabricated via accumulative roll bonding (ARB) process. To this purpose, AA1060/ Fe2O3 composite strips with thickness of 1 mm have been fabricated with up to eight ARB passes at 300[Formula: see text]C. In this study, magnetic Al/Fe2O3 composites reinforced with 0, 5% and 10 wt.% of Fe2O3 particles have been manufactured via ARB. The microstructure was studied by optical microscopy (OM). Also, by decreasing the thickness of layers at higher number of passes (increasing the plastic strain), the bonding quality among the layers was improved. Scanning electron microscopy (SEM) fracture surface morphology of samples after the tensile test showed that by increasing the passes, the fracture style (mode) converted to shear ductile at higher ARB passes. So, deep dimples shrink slowly and their number and depth decreased relative to the annealed sample. As the criterion of formability, the area under the FLDs dropped sharply after the first pass and then improved by increasing the passes. Results of fracture test have shown that the value of fracture toughness has been enhanced continually to the maximum value of 34.3 MPam[Formula: see text] at the 8th pass.

Evolution of the texture, microstructure, and magnetic properties of a Permimphy alloy after accumulative roll bonding and aging

Evolution of the texture, microstructure, and magnetic properties of a Permimphy alloy after accumulative roll bonding and aging

Deformation mechanisms in a novel multiscale hetero-structured Mg alloy with high strength-ductility synergy

Most of the high-strength Mg alloys exhibit poor ductility at room temperature. Architecturing appropriate heterostructure in metallic materials gives rise to the breakthrough of the inherent strength-ductility trade-off dilemma. Here, we prepared a novel multiscale hetero-structure in Mg-9Al-1 Zn (AZ91) alloy, consisting of bimodal-structured center-region and fine-grained surface-layer, providing high strength and high ductility, i.e. yield strength of ∼303 MPa, tensile strength of ∼400 MPa, and elongation of ∼14.5 %. The multiscale microstructural heterogeneities were induced via a simple rolling process that combines the advantages of both accumulative rolling bonding (ARB) and hard plate rolling (HPR). By utilizing quasi-in-situ electron backscattered diffraction (EBSD)-digital image correlation (DIC) characterizations combined with the determination of dislocation/disclination distributions, it has been found that diversified strain accommodation mechanisms are stimulated by the strain incompatibilities near hetero-interfaces in the multiscale hetero-structure. In particular, non-basal slips have been activated largely in both the bimodal-structured center-region and fine-grained surface-layer. Moreover, a unique slip trace distribution has been observed in the fine grains adjacent to the basal-oriented coarse grain. Such a strain accommodation can better coordinate local strain incompatibility among the hetero-interface. The uniaxial loading–unloading–reloading tensile loop tests demonstrate that the multiscale heterogeneities impart a pronounced hetero-deformation induced hardening during tensile deformation. Multiple deformation modes, including the non-Schmid and non-basal slips, have been activated substantially in the multiscale hetero-structured Mg alloy, effectively relaxing local stress concentration and achieving stable plastic flow at a high-stress state, which is beneficial to improving strain-hardening ability and strength-ductility synergy. Our work could shed light on designing and processing strong and ductile Mg alloys, by tailoring proper microstructural heterogeneity to activate cooperated accommodating deformation modes.