Equal Channel Angular Rolling Process Research Articles

Strength and formability improvement of ECARed aluminum alloy 6061 sheets using the artificial aging heat treatment

In the current research, the experimental investigation of the mechanical characteristics of 6061 aluminum alloy, which was subjected to Equal Channel Angular Rolling (ECAR) – A Severe Plastic Deformation Process – and artificial aging heat treatment, has been discussed. By performing the ECAR, the strength of the material increases, but the formability will be reduced. Consequently, the usage of this alloy has been limited. The artificial aging heat treatment process has been proposed after the ECAR operation, and the strength, hardness, and formability of the material have been investigated. In this regard, remarkable results were obtained. By controlling the aging time and temperature on the ECAR piece, not only the strength increased but also the ductility increased. Moreover, an artificial neural network was used to find the optimal aging time and temperature. Finally, the best aging time and temperature ranges to achieve the most desirable mechanical properties were provided using the neural network. The result show 150% increase in strength and 50% in formability by performing controlled-artificial aging heat treatment with ECAR process.

Role of unusual double-peak texture in significantly enhancing cold rolling formability of AZ31 magnesium alloy sheet

Multi-pass cold rolling experiments were performed on AZ31 magnesium alloy sheet with unusual double-peak texture, where basal poles tilt about ±40° away from normal direction to rolling direction. This adopted sheet was fabricated by a novel technology of equal channel angular rolling and continuous bending process with subsequent annealing. Experimental results confirm that such an unusual double-peak texture contributes to a huge improvement of accumulated reduction up to 39.2%, which is over twice as much as that (18.3%) in sheet with strong basal texture. Optical microscopy and electron backscatter diffraction measurements demonstrate that the evolution of microstructure and texture in sheet with unusual double-peak texture is quite different from that in sheet with strong basal texture. Schmid factor (SF) analysis confirms that sheet with unusual double-peak texture possesses obviously large SF values for basal 〈a〉 slip {1012} and extension twin (ET) and remarkably small SF values for prismatic 〈a〉 slip and pyramidal 〈c+a〉 slip during cold rolling process. Therefore, basal 〈a〉 {1012} slip and {1012} ET will be activated more frequently in sheet with unusual double-peak texture to sustain plastic strain, leading to significant enhancement in cold rolling formability.

Effects of equal channel angular rolling process on the mechanical properties of Al-Cu two-layer sheets: experimental and numerical approaches

Abstract This study investigates the mechanical properties and microstructural characteristics of explosion-welded Al/Cu two-layer strips during the ECAR process using finite element simulations and experiments. Furthermore, the explosion-welded Al/Cu two-layer strip was examined with various configurations to determine the effects of die angle and friction coefficient on the distributions of effective strain and stress. In addition, the experimental and computational approaches were utilized to explore the ECAR process in two routes, RA and RC, for three directions. Finite element simulations were run and validated using experimental data. The findings show that the ECAR method is effective to enhance the mechanical characteristics of the strips. Moreover, the obtained results represent that the ECAR process reduced the size of the grains. Furthermore, it was shown that by increasing the number of routes in the ECAR process, the stress values were increased. However, the ductility of the two-layer strip was decreased. According to the current study, the route and the number of routes used in the ECAR process have a considerable effect on the strength of the two-layer strip.

Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling.

The aim of the article is to examine the workability of sintered powder material of aluminum alloy (Alumix 321) through severe plastic deformations under the conditions of the equal channel angular rolling (ECAR) process. Accordingly, the stress-strain analysis of the ECAR was carried out through a computer simulation using the finite element method (FEM) by Deform 3D software. Additionally, the formability of the ALUMIX 321 was investigated using the diametrical compression (DC) test, which was measured and analyzed by digital image correlation and finite element simulation. The relationship between failure mode and stress state in the ECAR process and the DC test was quantified using stress triaxiality and Lode angle parameter. It is concluded that the sintered powder material during the ECAR processing failure by a shearing fracture because in the fracture location the stress conditions were close to the pure shear (η and θ¯ ≈ 0). Moreover, the DC test revealed the potential role as the method of calibration of the fracture locus for stress conditions between the pure shear and the axial symmetry compression.

Finite Element Analysis and Optimization of Equal-Channel Angular Rolling Process by Using Taguchi Methodology

Finite Element Analysis and Optimization of Equal-Channel Angular Rolling Process by Using Taguchi Methodology

Influence of bimodal non-basal texture on microstructure characteristics, texture evolution and deformation mechanisms of AZ31 magnesium alloy sheet rolled at liquid-nitrogen temperature

Cryogenic rolling experiments have been conducted on the AZ31 magnesium (Mg) alloy sheet with bimodal non-basal texture, which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A) process. Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%, which is about 105.6% larger than that of the sheet with traditional basal texture. Characterization experiments including optical microstructure (OM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD) measurements are then performed to explore the microstructure characteristics, texture evolution and deformation mechanisms during cryogenic rolling. Experimental observations confirm the occurrence of abundant {10–12} extension twins (ETs), twin-twin interactions among {10–12} ET variants and {10–12}-{10–12} double twins (DTs). The twinning behaviors as for {10–12} ETs are responsible for the concentration of c-axes of grains towards normal direction (ND) and the formation of transverse direction (TD)-component texture at the beginning of cryogenic rolling. The twinning behaviors with respect to {10–12}-{10–12} DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling. The involved deformation mechanisms can be summarized as follows: Firstly {10–12} ETs dominate the plastic deformation. Subsequently, dislocation slip, especially basal <a> slip, starts to sustain more plastic strain, while {10–12} ETs occur more frequently and enlarge continuously, resulting in the formation of twin-twin interaction among {10–12} ET variants. With the increasing rolling passes, {10–12}-{10–12} DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain. The activities of basal <a> slip, {10–12} ETs and {10–12}-{10–12} DTs benefit in accommodating the plastic strain in sheet thickness, which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling.

Mehaničke karakteristike legura AL-1050 i AL-6061 deformisanih korišćenjem ravnokanalnog procesa ugaonog valjanja

One of the effective severe plastic deformations (SPD) techniques is Equal channel angular rolling (ECAR) process which can lead to proper ultra-fine grained (UFG) structures of material, the main objective of this work is to study the improvement in mechanical properties within 1050 and 6061 aluminum alloy sheets. There are more attempts to investigate the microstructure and mechanical properties of strips material, the influence of process parameters such as number of equal channel angular rolling passes, routes (A&amp;C) and annealing temperature after each passes on deformation behavior of 6061 and 1050 Aluminum alloys were investigated experimentally .Results was indicated that for AL-6061 without annealing process at first pass it was the higher stress than the passes after annealing process and also the grains was fine in the first pass ,For AL-1050 it was indicated that with ambient temperature at six pass the mechanical properties was improved and its recorded the higher stress with more passes at six pass for rout C and also the fine grains of microstructure was obtained in the six pass with compared to the material with annealing process which becomes more ductility with more passes.

Effects of ECAR process on the mechanical properties of explosively welded Al/Cu/Al

ABSTRACT Equal channel angular rolling (ECAR) is a severe plastic deformation method that coated plastic deformation of sheets. This research aims to analyse the effects of equal channel angular rolling feeding routes and the number of passes on the mechanical properties of explosive-welded Al/Cu/Al multilayer sheets. Based on this study, three layers of metal sheets (Al/Cu/Al) were prepared through the explosive welding process to achieve the goals. This multilayer material been passed through the ECAR process, to investigate the number of passes affections and two different feeding routes (A and C) on the mechanical properties of the explosive welded samples. To examine changes in hardness and strength of ECAR samples, micro-hardness tests and uniaxial tensile tests were adopted. The results demonstrate that tensile strengths and microhardness increase for both routes by the ECAR process; however, it decreases the ductility. The yield strength of three layers of sheets has been increased from 92 MPa to 118 MPa and 126 MPa at the routes A and C, respectively. The results show that the toughness of the route A is greater than route C.

The effect of temperature on the mechanical properties and forming limit diagram of Al 5083 produced by equal channel angular rolling

The primary purpose of this research is investigating the effect of increasing temperature on mechanical properties and formability of Al 5083 produced by equal channel angular rolling (ECAR) process. The present work also aims to study the feasibility of increasing temperature as an approach for solving the ductility problem of ultrafine-grained Al 5083, although some strength of the material might be sacrificed. So, the quantitative and qualitative analysis of the effect of temperature increase on mechanical properties and formability has been done. In this paper, the ECAR process has been performed at three different temperatures (i.e., 25 °C, 200 °C, and 300 °C(. Then, the investigation of mechanical properties such as yield strength, ultimate tensile strength, and microhardness after each pass of the ECAR at different temperatures has been performed. The results showed that by applying the ECAR process at a specified temperature, the mechanical and microhardness properties of the samples improved, while elongation to fracture reduced. At ambient temperature, and after the 3rd pass of the ECAR process, yield strength, ultimate tensile strength, and microhardness compared with the annealed sample increased by 94%, 19%, and 52%, respectively. Also, the mechanical properties of samples after the ECAR process in a specified pass at different temperatures have been evaluated. The obtained results showed that by increasing temperature, the yield strength, ultimate tensile strength, and microhardness of the samples decreased, but the elongation to fracture as well as the forming limit diagram (FLD) improved. The results illustrated that by applying the ECAR process at a specified temperature, the level of the FLDs moved downward. Also, the FLDs after the 3rd pass of the ECAR at different temperature have been compared. The results showed that the FLD0 (the major forming limit strain in-plane strain mode) at a temperature of 200 °C and 300 °C compared with the ambient temperature increased by 5% and 20%, respectively.

Effect of texture types on microstructure evolution and mechanical properties of AZ31 magnesium alloy undergoing uniaxial tension deformation at room temperature

Influence of texture type on mechanical properties and the evolution of microstructure and texture is thoroughly investigated via uniaxial tension experiment along rolling direction (RD) at room temperature on two different AZ31 alloy sheets. Electron backscattered diffraction (EBSD) measurements on deformed samples confirm that dislocation slip is the main deformation mechanism in as-received sheet with a typical basal texture, while dislocation slip and extension twinning (ET) both contribute to sustaining plastic strain in the sheet with a rare RD-split bimodal texture, which is fabricated by equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A). Therefore, these two sheets demonstrate obviously different texture evolution during plastic deformation. As-received sheet maintains basal texture and further experience the concentration of basal poles towards normal direction (ND). However, ECAR-CB-A sheet not only undergoes the gradual diffusion and rotation of tilted basal poles to ND but also the development of a new TD-component texture. The activation of ET variants in ECAR-CB-A sheet is confirmed to play an important role in texture evolution, and the number of activated ET variants is increasing with the increase of angle between ND and c-axis. In addition, acquired mechanics data demonstrate that ECAR-CB-A sheet possesses higher fracture elongation (24%) and lower yield stress (73 MPa) as compared to as-received sample. This issue can be ascribed to the participation of ET to coordinate plastic deformation along c-axis and the easier activation of basal <a> slip in ECAR-CB-A sheet.

Effect of Equal Channel Angular Rolling Process on the Fracture Mechanisms of Al-7057 and Al-5052 Alloys

Fracture is one of the main criteria in designing industrial structures that its exact comprehension is highly significant in new sciences. This study analyzes the effect of equal channel angular rolling (ECAR) process on fracture mechanics in Al-7075 alloy ECARed through two routes of A and C and in Al-5052 alloy ECARed through the route of C. The results of analyzing fracture surfaces of samples, using scanning electron microscope, indicate that fracture has been ductile in samples without application of the process, on which a combination of shear and ductile fracture appeared after application. Moreover, it was observed that ECARed Al-7075 samples in route A have been fractured more in comparison with ECARed samples in route C. Also, the yield and tensile strengths increased and elongation decreased with increasing the number of passes in each pair of sheet.

Correlation Between Structural Parameters and Mechanical Properties of Al5083 Sheets Processed by ECAR

In the paper, structural parameters and mechanical properties of Al5083 alloy sheet during equal channel angular rolling (ECAR) process and their relationship are studied. In order to evaluate the effect of ECAR process, Al5083 strips were subjected to the ECAR process for 1, 2, and 3 passes through the die channel angles 110°, 120°, and 130° at two routes. The effect of the process on the microstructural evolution of samples was investigated by means of x-ray diffraction and EBSD techniques. X-ray pattern has been analyzed using Rietveld method to compute structural parameters, including microstrain, average crystallite size, and dislocation density. The results showed that the dislocation density and microstrain were increased, and crystallite size was decreased during ECAR process. It was found that the behavior of variations in mechanical properties was in accordance with the dislocation density changes. This paper revealed that the increase in the strength of ECARed samples could be attributed to reduction in high-angle grain boundaries and the increase in dislocation density. Moreover, the yield strength estimated from Taylor equation was found in accordance very well with the experimentally measured yield strength of the samples.

Tribological and Geometrical Analysis of the Friction Forces of Continuous Severe Plastic Deformation

Equal Channel Angular Rolling (ECAR), a severe plastic deformation process, is suitable for the shear deforming a long and thin sheet continuously. An interesting issue is that thickness of a sheet is not reduced during ECAR. Although the shear texture and fine grain structure are easily obtained by ECAR, yet the ECAR process’s difficulties in terms of technical control, such as surface defect, low ductility and low processing speed, still remain. The surface defects and processing speed are partially improved by applying a series deformation of rolling and ECAR. The article presents methodological and analytical procedures, adaptation of a conventional rolling mill Duo-system for processes of a SPD-representative which are represented by the method ECAR. They specify in detail the technical requirements whose new design solutions should be implemented. They present in detail the mechanical load drive shafts, as well as the calculation of compression forces with consideration of the friction forces. The geometric analyses of localisation positions of the outlet channel in terms of size and orientation of the dominant shear plane are also presented.

Fatigue behavior of nano-grained pure copper processed by equal channel angular rolling

The equal channel angular rolling process was successfully performed on commercial pure copper. After 4 passes of this process, grains with a diameter of about 70- 500 nm were formed. The fatigue test results showed that the ultra-fine grained copper represents a longer lifetime under stress-controlled fatigue. To clarify the formation process of surface damage, morphological changes in the fractured surface were monitored by scanning electron microscopy.

Uncertainty analysis of residual stresses measured by slitting method in equal-channel angular rolled Al-1060 strips

Residual stresses can meaningfully influence on the operation of a part. They are almost created by all fabrication processes. In this study, slitting method was used to obtain the residual stress profile through the thickness of equal-channel angular rolled aluminum strips. Furthermore, uncertainty analysis of the measured residual stresses was performed. The measurement and model uncertainties were considered in the uncertainty analysis, and the effect of each one on the total uncertainty was investigated. Besides, to study the through-depth residual stress distribution numerically, finite element simulation of equal-channel angular rolling process in route C was done. In route C, the strip should be rotated around the longitudinal axis by 180° after each successive pass. The results showed the important role of both measurement and model uncertainties in the calculation of total uncertainty. The maximum tensile residual stresses of the control, 1-pass and 2-pass samples were 7.59, 64.4 and 85.11 MPa, respectively, and the root mean square total uncertainty of them were 1.47, 2.43 and 5.12 MPa, respectively. There was a good agreement between experimental and numerical results.

Effect of Accumulative Roll Bonding and Equal Channel Angular Rolling on Microstructural and Mechanical Properties of Cu–Al–Mn Shape Memory Alloys

Two Cu-based shape memory alloys, Cu–9.5Al–8.2Mn and Cu–8.3Al–8Mn (in wt%), were chosen for the present study and subjected to severe plastic deformation by accumulative roll bonding (ARB) and equal channel angular rolling (ECAR) processes, respectively. The effects of ARB and ECAR processes with subsequent post-deformation annealing on the transformation temperatures, microstructure and mechanical properties of these alloys were investigated. The ARB process was carried out at 600 °C, followed by post annealing at 700 °C for different lengths of time. The ECAR process was performed in 5 passes at room temperature, followed by post annealing at 890 °C for different lengths of time. Scanning electron microscopy studies revealed that the coexistence of bainitic and martensitic structures was the main reason for enhancement of mechanical properties of Cu–8.3Al–8Mn alloy. It also revealed that the enhancement of tensile properties of Cu–9.5Al–8.2Mn alloy could be directly attributed to the grain refinement induced by ARB and post deformation annealing. For both alloys, transformation temperatures reduced and selective growth of martensite variants occurred after post-deformation annealing.

Applicability of Artificial Neural Network and Nonlinear Regression to Predict Mechanical Properties of Equal Channel Angular Rolled Al5083 Sheets

Equal channel angular rolling (ECAR) is a severe plastic deformation (SPD) process in order to achieve ultrafine-grained (UFG) structure. In this paper, the mechanical properties of ECAR process using artificial neural network (ANN) and nonlinear regression have been illustrated. For this purpose, a multilayer perceptron (MLP) based feed-forward ANN has been used to predict the mechanical properties of ECARed Al5083 sheets. Channel oblique angle, number of passes and the route of feeding are considered as ANN inputs and tensile strength, elongation and hardness are considered as the outputs of ANN. In addition, the relationship between input parameters and mechanical properties were extracted separately using nonlinear regression method. Comparing the outputs of models and experimental results shows that models used in this study can predict and estimate mechanical properties appropriately. Where, the performance of ANN model is better than the correlations to predict mechanical properties. Finally, the developed outputs of neural network model are used to analyze the effects of input parameters on tensile strength, elongation and hardness of ECARed Al5083 sheets.

Numerical and experimental studies on deformation behavior of 5083 aluminum alloy strips in equal channel angular rolling

Improvement of mechanical properties of metal strips can be achieved by producing ultra-fine grained microstructure. The equal channel angular rolling process is one of the effective severe plastic deformation techniques which can lead to proper ultra-fine grained structures. In this research, the influence of process parameters such as pre–equal channel angular rolling annealing temperature, number of equal channel angular rolling passes, routes and post–equal channel angular rolling annealing on deformation behavior of 5083 Al alloy is investigated by experimental studies and numerical simulations. Metallurgical investigations revealed that grain refinement and increased dislocation density are two effective parameters on the mechanical strength improvement. The investigation of mechanical properties demonstrated that increasing number of equal channel angular rolling passes leads to a considerable increase in yield stress, ultimate tensile strength and hardness. In contrast, elongation was dramatically reduced. Also, improvement of mechanical properties reaches saturation at a critical strain level, depending on the microstructure evolution. In addition, investigation of effects of post–equal channel angular rolling annealing on the specimens annealed at 415 °C indicated that elongation and toughness increase, accompanying with a low decrease in yield and tensile strengths and hardness. In this study, the equal channel angular rolling process was numerically simulated using ABAQUS software in two different routes for three passes. It is shown that upper roller force is increased by increasing the number of equal channel angular rolling passes, but the rate of this increase is reduced at higher passes.

Forming limit diagrams of fine-grained Al 5083 produced by equal channel angular rolling process

The objective of this research is to study the strain forming limits of Al–Mg alloy (5083) sheet, fabricated by equal channel angular rolling process at room temperature. For this purpose, the equal channel angular rolling process was executed at room temperature in three passes. Mechanical properties, microhardness, and microstructure were investigated after the equal channel angular rolling process. Uniaxial tensile tests of the equal channel angular rolling process produced samples and showed that yield and ultimate stresses increase, while the uniform elongation to fracture decreases in comparison with the annealed state. There was a continuous hardness enhancement by increasing the number of the equal channel angular rolling passes. After the third pass, the amount of hardness raised by 73% in comparison with the annealed sample. In the fourth pass, the hardness reduced slightly, that was attributed to the strain saturation in room temperature and was followed by high surface cracks. In the annealed condition, the average grain size was 45 µm, and after the third equal channel angular rolling pass, this amount was reduced to 10 µm. Furthermore, the forming limit diagrams were determined experimentally, using the Nakazima test. The obtained results show that after the third pass, the forming limit diagrams’ level move downward, meaning that a reduction occurred in the forming limits of equal channel angular rolled samples.

Investigation of residual stress and mechanical properties of equal channel angular rolled St12 strips

Equal channel angular rolling process is defined as a severe plastic deformation method that imposes very large plastic strain on a material in order to enhance its mechanical properties and grain structure refinement. In this study, residual stress profiles through the thickness of St12 strips that were subjected to different passes of equal channel angular rolling were investigated by slitting method. Also, the effects of different routes of equal channel angular rolling (A and C) were studied on the mechanical properties and residual stress. Furthermore, the effect of post annealing on the mechanical properties and residual stress of 4-pass equal channel angular rolled strip was examined. The results showed significant increase in the yield strength, ultimate tensile strength, and micro hardness of the samples in both routes. But the elongation decreased. Considerable magnitude of residual stress was created through the thickness of equal channel angular rolled samples such that the maximum tensile residual stress of some samples raised to about half of the corresponding yield strength. The maximum magnitude of residual stress in route C was smaller than that in route A.