Equal Channel Lateral Extrusion Research Articles

Comparing the microstructural and mechanical improvements of AZ80/SiC nanocomposite using DECLE and MDF processes

The present study investigates the effects of two different severe plastic deformation (SPD) processes on an annealed AZ80/SiC nanocomposite. Specifically, the microstructure, texture, shear behavior, and hardness of the material were analyzed after being subjected to dual equal channel lateral extrusion (DECLE) for up to 5 passes, and multidirectional forging (MDF) for up to 8 passes, both carried out at a constant temperature of 300 °C. The effective strain was 1.44 and 0.5 in each DECLE and MDF pass. The annealed AZ80/SiC nanocomposite showed a reduction in average grain size from 68.4 μm to 2.7, 4.2, and 4.4 μm during 1, 3, and 5 passes of DECLE process, and to 8, 4.3, 2.3, and 5.4 μm during 2, 4, 6, and 8 passes of MDF process. Examination of the shear properties revealed that the ultimate shear strength (USS) of the nanocomposite increased after conducting both the DECLE and MDF processes. Specifically, the USS of the annealed nanocomposite increased by 23.1 MPa after 5 passes of the DECLE process and by 8.1 MPa after 8 passes of the MDF process. These results indicate that the DECLE process had a greater effect on the shear strength increase compared to the MDF process. The results of the hardness testing on the AZ80/SiC nanocomposite showed that the fifth pass of the DECLE process increased the hardness from 86.6 to 96.2 Hv, while the eighth pass of the MDF process increased this value to 90.1 Hv. The DECLE process was found to be more effective than the MDF process due to the simultaneous application of three types of shear deformation, pressing, and extrusion in each pass, as well as the higher effective strain.

Study on the Improved Mechanical Properties of RAFM Steel After Dual Equal-Channel Lateral Extrusion: Reflected by Quantified Microstructure

Study on the Improved Mechanical Properties of RAFM Steel After Dual Equal-Channel Lateral Extrusion: Reflected by Quantified Microstructure

Microstructure and hot shear deformation behavior of a fine-grained AA5083 aluminum alloy

Dual Equal Channel Lateral Extrusion (DECLE) was performed in different passes on an annealed AA5083 aluminum alloy. The microstructural evolution of the alloy was investigated using electron backscatter diffraction images and the dislocation density was determined by X-ray line profile analysis. It was found that DECLE is effective in grain refinement, and while dislocation density is almost saturated after the fourth pass of DECLE, applying the sixth pass results in more grain size reduction of annealed sample from 59.2 μm to 3.8 μm. To assess the mechanical behavior of the DECLE-processed materials, shear punch tests (SPT) at high temperatures (300–400 °C) and various strain rates (3×10−3−3×10−1s−1) were conducted. The shear stress-normalized displacement curves obtained from SPT were utilized to obtain the material constants such as the stress exponent (n) and the activation energy (Q) in the hyperbolic-sine constitutive model. The variations of n and Q were analyzed based on the microstructural features such as grain size, HAGBs fraction, dislocation density, and second phase particles fraction. The results suggest that the Q value is competitively influenced by these parameters. Accordingly, finer grain size, higher HAGBs volume fraction, lower second phase volume fraction, and smaller dislocation density result in lower Q values.

Hot shear deformation constitutive analysis of fine-grained ZK60 Mg alloy sheet fabricated via dual equal channel lateral extrusion and sheet extrusion

Dual equal channel lateral extrusion (DECLE) process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets. The coarse grain structure of the annealed sample after applying sheet extrusion (size: 68 µm) changed to fine grains of 6.0 and 5.2 µm after 3 and 5 passes of DECLE and following extrusion. The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test (SPT) results. SPT was carried out in the temperature range of 200−300 °C and strain rate range of 0.003−0.33 s–1. The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions, which indicated that dislocation creep, controlled by dislocation climb and solute drag mechanism, acted as the main hot deformation mechanism. It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction, and the relationship of which was anticipated using a 3D surface curve. Moreover, the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.

Improving both Strength and Ductility of Al-7075 by combining Dual Equal Channel Lateral Extrusion with Aging Heat Treatment

Improving both Strength and Ductility of Al-7075 by combining Dual Equal Channel Lateral Extrusion with Aging Heat Treatment

Investigating the Microstructure, Hardness and Tensile Behavior of Magnesium AZ80 Alloy and AZ80/SiC Nanocomposite Manufactured Through Dual Equal Channel Lateral Extrusion (DECLE)

In this study, first, AZ80 magnesium alloy and AZ80/SiC nanocomposite were manufactured through a stir casting approach. Then built samples underwent five passes of DECLE process at a constant temperature of 300 °C. Changes in microstructures, hardness, and tensile strength were measured in the annealed alloy and nanocomposites as well as samples with 1, 3, and 5 passes of DECLE to determine the effects of sic. strengthening nanoparticles and number of the DECLE passes. Results show that there is a most significant decrease in grain size due to adding the nanoparticles. The microstructure of the initial AZ80 samples made by large grains and inhomogeneous structure with an average grain size of 60.3 µm. After five DECEL passes for samples with nanoparticles, the structure is turned into fine and homogenous grains with an average size of 4.5 µm. Along with this decreasing trend in the grain size, hardness shows a 20.7% increasing. The results of the uniaxial tensile test show that yield strength and ultimate tensile strength have increased respectively from 74 to 131.8 MPa for initial samples to 113 and 221.9 MPa in nanocomposites. Finally, their values reach to 191.3 and 288.3 MPa after applying five passes of DECLE process. The results indicate that it is possible to significantly improve the microstructure and mechanical properties of the AZ80 magnesium alloy through enriching by nanoparticles. Using severe plastic deformation processes such as DECLE can induce a further decrease in grain size and significant improvement in the mechanical properties without causing changes in the samples’ dimensions.

High temperature behavior of severely deformed AA 5083 through equal channel lateral extrusion

Describing the high temperature behavior of a fine-grained AA 5083 aluminum alloy using an improved constitutive model is the focus of this paper. Dual Equal Channel Lateral Extrusion (DECLE) was utilized to create fine-grain microstructure in AA 5083 aluminum alloy. EBSD confirmed the formation of fine-grain microstructure after 5 passes of DECLE. The hot deformation behavior of the DECLEd alloy was assessed by hot compression tests at temperatures of 200–275 °C and strain rates of 10−4-10−1 s−1. The material constants, A, n and Q, in the hyperbolic-sine constitutive equation were calculated at peak stresses. The results suggested that the grain size affects the values of α and n, while the activation energy (Q) is more or less independent of the grain size. The values of α and n for the fine-grain material were obtained as 0.004357 (MPa−1) and 9.97, respectively. These calculated values (α and n) are respectively lower and higher than those reported for a coarse-grain one in the literature. This result was related to the high flow stress of the refined microstructure. The value of Q showed that the dislocation-dispersoid interactions are the rate-controlling mechanism during hot deformation. By iterating the calculation of constants at various strains, a strain-compensated constitutive equation was proposed for the prediction of flow stress over a wide range of strain. Finally, the processing maps were developed for the AA 5083 alloy at various strains.

Influence of Combined Severe Plastic Deformation and Sheet Extrusion Process on the Superplastic Formability of AA 5083 Aluminum Alloy Assessed by Free Bulge Test

A combination of two forming operations is considered for producing metal sheets with improved mechanical properties. As the first operation, a newly introduced severe plastic deformation method called dual equal channel lateral extrusion (DECLE) was performed at 300 °C for different passes on the AA 5083 aluminum blocks. Following the DECLE operation, sheet extrusion was conducted to convert the bulk samples, severely deformed through various passes, into 1.8-mm-thick sheets. Mechanical properties of the processed specimens, after each step of deformation, were examined using tensile and shear punch tests. It was found that the material after three passes of DECLE and also the corresponding forwardly extruded sheet presented the greatest strength. In order to evaluate the biaxial formability of the sheets, gas bulge forming tests were conducted using a PLC-controlled gas circuit. It was shown that the material processed via three passes of DECLE operation and extrusion demonstrated the maximum biaxial superplastic formability with an effective strain associated with 400% uniaxial elongation. This sheet specimen also required the minimum forming time, coinciding with a strain rate of 4 × 10−4 s−1, which is higher than strain rate for the sheet extruded from the annealed sample.

Significant improvements in mechanical properties of AA5083 aluminum alloy using dual equal channel lateral extrusion

Dual equal channel lateral extrusion (DECLE), as a severe plastic deformation (SPD) process, was employed for improving the mechanical properties of AA5083 aluminum alloy. Several experiments were conducted to study the influences of the route type, namely A and B, and pass number on mechanical properties of the material. The process was conducted up to 6 passes with decreasing process temperature, specifically from 573 to 473 K. Supplementary experiments involving metallography, hardness and tensile tests were carried out in order to evaluate the effects of the process variables. The hardness measurements exhibited reasonably uniform distributions within the product with a maximum increase of 64% via a 6-pass operation. The yield and ultimate strengths also amended 107% and 46%, respectively. These significant improvements were attributed to the severe shear deformation of grains and decreasing pass temperature, which intensified the grain refinement. TEM images showed an average grain size reduction from 100 µm for the annealed billet to 200 nm after 6 passes of DECLE. Finally, the experimental findings for routes A and B were compared and discussed and some important conclusions were drawn.

Improvements in microstructure and mechanical properties of AZ80 magnesium alloy by means of an efficient, novel severe plastic deformation process

Present paper includes efforts to develop dual equal channel lateral extrusion (DECLE) into an efficient SPD technique for processing tubular samples. In modified technique, entitled H-tube pressing (HTP), specimen accumulates outstanding amount of plastic strain in a couple of half cycles. Theoretically imposed plastic strain by means of the HTP operation exceeds that is attainable via a wide range of SPD methods. In this research work, the HTP process was experimentally conducted up to 2 passes (4 half cycles) on as-cast AZ80 magnesium alloy at elevated temperature. The microstructural and mechanical improvements follow the HTP process were investigated. Findings revealed that by conducting the first half cycle of HTP process, the average grain size reduced by 73%. Moreover, the yield stress and the elongation were increased by 90% compared to as-cast condition while the ultimate tensile strength and the microhardness were improved by 100 and 58%, respectively. Stability of mechanical properties of AZ80 alloy was observed at the end of the first half cycle. These results imply that HTP can be employed as an efficient, single-pass operation.

High strain-rate superplasticity of fine- and ultrafine-grained AA5083 aluminum alloy at intermediate temperatures

Abstract Superplastic behavior of fine and ultra fine-grained AA5083 Al alloy was examined using the shear punch test. To achieve fine- and ultra fine-grained microstructures, a relatively new severe plastic deformation (SPD) process, namely Double Equal Channel Lateral Extrusion (DECLE) was employed. The strain rate sensitivity indices (m) of samples were evaluated after 1, 2, 4, and 6 passes for shear strain rates in the range of 3 × 10− 3 to 3 × 10− 1 s− 1 and temperatures in the range of 573 to 673 K. For microstructural observations, TEM images together with the corresponding SAED patterns were prepared and utilized. A considerable increase in the m-value was observed after the first pass of the operation for all testing temperatures. The best condition for achieving a good superplasticity for the alloy was found to be a single pass DECLE at 673 K in the strain rate range of 10− 2 to 10− 1 s− 1. This process condition resulted in an m-value of 0.43, indicative of a high strain rate superplastic deformation behavior. Further passes of the SPD process did not show any sign of superplasticity until the last pass of the operation, during which the m-value slightly increased, compared with the previous pass.

Effects of die geometry on non-equal channel lateral extrusion (NECLE) of AZ80 magnesium alloy

Non-equal channel lateral extrusion (NECLE) is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion (ECLE). The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.

Effect of friction in Dual Equal Channel Lateral Extrusion using finite element simulation

Dual equal channel lateral extrusion (DECLE) is a type of equal channel angular pressing which employs T-shaped die instead of L-shaped die. In the present work, deformation behavior in the DECLE process is analyzed by using DEFOEM-2D. The effect of friction between the die channels and the specimen on the effective strain distribution homogeneity and load were investigated. The friction induces inhomogeneous deformation in the head, top and bottom regions of the work piece. As friction increases, the top gap becomes smaller and the strain distribution becomes more homogenous, but the maximum load value increases. These results can serve as a design for reasonably technological parameters for DECLE processing.

Microstructural and Mechanical Properties of Al 7003 Alloy Processed by Dual Equal Channel Lateral Extrusion

In this paper, the Al 7003 alloy in the as-annealed condition was processed by dual equal channel lateral extrusion (DECLE) at room temperature. The microstructure and mechanical properties of the as-annealed and DECLEed alloys were examined. The results showed that the microstructure of as-annealed Al 7003 alloys was refined by the formation of deformation bands, with dislocation cells and subgrains inside these bands. The final grains with an average size of about 250nm are observed. Due to DECLE, tensile yield strength and ultimate tensile strength increase by 84.5%, 35.4%, respectively. Meanwhile, elongation to failure decreases by 40.4%. The fracture was characterized by ductile fracture due to existence of a large number of dimples.

Microstructural and mechanical properties of commercially pure aluminum subjected to Dual Equal Channel Lateral Extrusion

This paper aims to provide an introductory insight about “Dual Equal Channel Lateral Extrusion”, a counterpart of “Equal Channel Angular Extrusion”. The process is implemented to severely refine the microstructure of aluminum slabs. Comparisons of macroscopic parameters as average straining and large scale distribution of strain, as well as process loads reveal the supremacies and short comings of DECLE with respect to ECAE. DECLE shares a relatively similar geometry of deformation with that of ECAE. The advantages of this process with respect to ECAE are: (i) more intensive strains attainable per pass, and (ii) less extruding power needed for a given sample size. Nonetheless, less homogeneous strain per pass is seen in case of DECLE. TEM inspections revealed remarkable refinement of the microstructure through out the process and also some recrystallization at the final passes. Hardness tends to increase through successive passes to a limiting value beyond which there appeared a decline associated with intense recovery and the recrystallization observed. Compression tests exhibit the same trend, viz. a general rise in strength followed by a decrease in work hardening with increasing number of passes, leading to uniform microstructure and hardness after 9 passes.

Upper-bound analysis of dual equal channel lateral extrusion

An upper-bound analysis is conducted for the newly introduced material processing method, “dual equal channel lateral extrusion”. The strain attained in the process is calculated by via the mean effective strain rate and deformation time, and then incorporated with the upper-bound formulation on power to yield an estimation of the extrusion pressure needed for the process. The estimated strain shows a good agreement with the previous works done for “channel angular deformation” which presumed an ideal deformation mode. The analytical extrusion pressure is then compared with the values obtained by experiments and showed that the analysis is capable of a good assessment of the process.