Number Of Equal Channel Angular Pressing Passes Research Articles

Effect of equal channel angular pressing on magnesium alloys − A review

Magnesium (Mg) alloys own excellent properties that includes better castability, low density and great specific strength. Mg and its alloys are easily available and economical. Necessity of Mg and its alloys for manufacturing and engineering purposes has increased, predominantly in the area of aircraft and automobile applications. The known limitation of magnesium is its poor formability at room temperature, with inadequate slip systems due to hexagonal closed packed construction of magnesium. Formability of magnesium alloys will be enhanced at room temperature by grain structure refinement which improves ductility with grain refined structure. Severe plastic deformation (SPD) procedure induces extreme strain within the sample to produce ultrafine grained structure. Additionally, few shortcomings of magnesium is increased wear mass loss and corrosion rate obstructing the use of Mg and its alloys in several industrial appliances. Wear resistance and corrosion behaviour can be enhanced by SPD thereby increasing the requirement of magnesium alloys for engineering applications. Among SPD, equal channel angular pressing (ECAP) is an efficient approach to develop and vary the mechanical and microstructural properties as per the need. In ECAP approach, the workpiece undergoes shear deformation and large strains are induced in the workpiece with no variation in cross sectional aspect of the workpiece. Microstructure plays a very important role in achieving the required mechanical properties. ECAP process creates ultrafine-grained microstructure with different number of ECAP passes with varying temperatures inducing high strain rate.

Mechanical properties and microstructure of Al–Mg (5052) alloy processed by equal-channel angular pressing (ECAP) with variation of ECAP routes and heat treatment

Equal-Channel Angular Pressing (ECAP) has become an effective technique of severe plastic deformation designed to produce ultrafine grain metals with improved mechanical properties, such as a good combination of strength and ductility. A report on the effect of ECAP routes on the mechanical and microstructure of commercial 5052 aluminum alloy needs also to be included. This work has been undertaken, in order to obtain the results. In this work, several deformation routes were used to process the Al – Mg (5052) alloy, namely A, Ba, Bc and C. Deformation route A involved repeatedly pushing the sample into the ECAP die without rotation, route Ba was performed by rotating the sample through 90° in alternate directions between each pass, route Bc by rotating the sample 90° in the same sense between each pass and route C by rotating the sample 180° between passes. The addition of the pass number decreases the grain size of ECAP-processed samples when compared to the as-annealed sample. It also confirmed that the microstructure of the 8-pass samples shows a finer grain size than the as-annealed sample. Furthermore, the Bc route (samples rotated in the same sense by 90° between each pass) has been proven to be the most effective deformation route, in order to obtain equiaxed ultrafine grain structure when compared to other deformation routes. This phenomenon takes place due to the continuous deformation in all cubic planes. The restoration after the 4-pass number will lead to the rapid evolution of sub-grains to high-angle grain boundaries, forming equiaxed grains. The characterization of the hardness number also shows that the addition of the ECAP pass number increases the hardness number of 5052 aluminum alloy, where samples processed with the Bc route indicate the highest hardness number at 168.4 HB. Moreover, a similar phenomenon also suggests that the tensile strength of all ECAP deformation routes has comparable values. The effect of heat treatment for samples with the Bc route also shows that 200 °C annealed samples have the highest hardness number and tensile strength when compared to other samples.

Effect of number of ECAP passes on structure and mechanical properties of Al–Ca–Mn–Fe alloy

The effect of number of equal-channel angular pressing (ECAP) passes on the structure and mechanical properties of the as-cast 4% Ca–1.3% Fe–0.8% Mn–0.1% Zr–0.1% Sc Al alloy is studied. ECAP was carried out at room temperature, through BC path using an angle between the channels of 110°. The number of ECAP passes was N = 2, 3, and 4. The as-cast alloy consisted of the solid solution dendrites (Al) and the [(Al) + Al10CaFe2 + Al4Ca] eutectic, as well as of a small fraction of the Al6(Fe, Mn) particles. As a result of ECAP, the dendrites are elongated approximately at an angle of 30° relative to the direction of ECAP. After two passes of ECAP, the dislocation density increased, but with an increase in the number of passes, the dislocation density slightly decreased as a result of the rearrangement of the dislocation structure; besides calcium segregated from the eutectic. After ECAP, a significant hardening of the alloy was observed. The highest strength observed after two passes (the ultimate tensile strength of the as-cast alloy was 130 MPa, and after the second pass it was 305 MPa), and the lowest one was after four passes (the ultimate strength was 219 MPa). The relative elongation of the ECAP-processed samples did not depend on the number of passes and it was about 1%.

Effect of CaO Addition on Microstructural Evolution Due to the Annealing of AZ31 Alloys Processed by Equal-Channel Angular Pressing (ECAP)

This study demonstrated the application of equal-channel angular processing (ECAP), which was performed via the BC route, to determine the effect of the addition of CaO on the microstructural evolution of an AZ31 alloy due to annealing. Compression tests were performed to evaluate the mechanical properties of the alloy, and the corresponding microstructures were observed to elucidate the flow behavior. Ca-bearing second-phase particles were fragmented with the increase in the number of ECAP passes. The increase in the yield strength and flow stress with the addition of CaO was attributed to the dispersion of the Ca-bearing second-phase particles. When the CaO-added AZ31 and commercial AZ31 alloys were subjected to annealing, their flow stress decreased owing to the grain growth. However, the extent of the decrease in the flow stress for the CaO-added AZ31 alloy was lower than that for the commercial AZ31 alloy.

Enhancement of Mechanical Behaviors and Microstructure Evolution of Nano-Nb2O5/AZ31 Composite Processed via Equal-Channel Angular Pressing (ECAP)

The automobile industry uses magnesium for load-bearing components due to its low density, durability, and ductility. This study investigated a nanocomposite containing Nb2O5 (3 and 6 wt%) nanoparticles as reinforcement with AZ31 magnesium alloy made by stir casting. A severe plastic deformation was conducted on the cast samples via equal-channel angular pressing (ECAP) after homogenization at 410 °C for 24 h and aging at 200 °C for 10 h. The microstructural distributions and mechanical properties of the magnesium metal matrix composites (MMCs) reinforced with Nb2O5 nanoparticles were investigated via ECAP. With the increase in the number of ECAP passes, the grain sizes became uniform, and the size of secondary phases reduced in the pure Nb2O5/AZ31 MMC. The grain size decreased remarkably after the ECAP process from 31.95 µm to 18.41µm due to the dynamic recrystallization during plastic deformation. The mechanical properties of hardness, ultimate tensile strength, and elongation effectively improved after each ECAP pass. The maximum values achieved for the Nb2O5/AZ31 composite subjected to ECAP were 64.12 ± 12 HV, 151.2 MPa, and 52.71%.

Effect of equal channel angular pressing on the mechanical properties of homogenized hybrid AZ61 magnesium composites

This study addressed the development and investigation of an AZ61 hybrid composite (HBC) fabricated by the stir casting method followed by equal channel angular pressing (ECAP). The HBC was reinforced using both Al 2 O 3 and SiC nanoparticles. The microstructural examination showed that the introduced reinforcements broke down the round-like formed precipitates into needle-like shapes that enhanced the ductility. Furthermore, the grain size of the HBCs is highly reduced while increasing the number of ECAP passes due to dynamic recrystallization (DRX). The obtained mechanical properties showed that the optimal yield strength (YS), ultimate tensile strength (UTS), and elongation were observed in the AZ61+2%Al 2 O 3 +1%SiC hybrid composite after two passes of ECAP. The Hall Petch strengthening mechanism was primarily responsible for the improved mechanical properties of AZ61 HBC, jointly with the mutual contribution of several mechanisms, including the coefficient of thermal expansion, Orowan looping, and load transfer mechanisms. • AZ61/Al2O3/SiC hybrid composite was produced by stir casting followed by ECAP. • Due to dynamic recrystallization, grain size was highly reduced during ECAP. • The mechanical characteristics of HBC enhanced after the each ECAP pass.

Microstructure, mechanical properties and fracture toughness of ECAPed magnesium matrix composite reinforced with hydroxyapatite ceramic particulates for bioabsorbable implants

Employing ceramic particles like hydroxyapatite to fabricate magnesium-based bio-composite has received incredible attention in orthopedic applications due to their bioactivity and biocompatibility. Besides, applying severe plastic deformation methods like equal channel angular pressing (ECAP), in addition to eliminating defects induced by casting, causes the metallurgical and mechanical behavior improvement of Mg/HA bio-composites. In this paper, the combined effects of HA particles and the ECAP process with Bc route on the microstructure, mechanical properties, and fracture toughness behavior of Mg/HA bio-composite fabricated through the electromagnetic and mechanical stir casting method were evaluated. Furthermore, a non-contact digital image correlation (DIC) method was adopted to accurately assess the elastic and plastic parameters and crack propagation during the fracture toughness test. Microstructural observation demonstrated that the addition of HA particles and, subsequently, applying four passes of the ECAP process on the bio-composites not only decreased the grain size by a considerable amount of 92%, but also resulted in a homogenous microstructure. Moreover, according to the results of the mechanical tests, after four-pass ECAP, although the compressive yield stress of Mg/HA bio-composite did not significantly change, the highest tensile yield stress, ultimate tensile, and compressive strength were accomplished. Among all elastic and plastic parameters, the elastic modulus and strength coefficient have continuously risen with adding HA and increasing the number of ECAP passes. However, the strain hardening exponent has decreased noticeably with the addition of HA, and the ECAP process compensated for some of this reduction. In addition, reinforcing magnesium with HA particles and improving the dislocation density caused by increasing the number of ECAP passes has led to increased material resistance against crack growth, wasted energy, and, consequently, fracture toughness. In this case, the four-pass ECAPed bio-composite showed the highest fracture toughness, approximately 28 MPa m0.5, 70% more than the pure Mg.

Grain refinement of Al–Zn–Mg alloy during equal channel angular pressing (ECAP)

Locally produced Al–Zn–Mg alloy was subjected to severe plastic deformation through Equal Channel Angular Pressing (ECAP) technique at temperatures of 150 °C and 200 °C. Rectangular thick-walled medium carbon steel die (σc = 450Mpa, σy = 176Mpa) with an L-shaped channel of uniform configuration to provide the pressing chamber was used. Four ECAP passes were imposed consecutively on set of samples for 150 °C and 200 °C temperatures, and characterized with optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). The phases were identified by X-ray diffraction (XRD) using monochromatic Cu Kα radiation, while vickers’ microhardness and tensile tests were performed for mechanical properties examination. Optical micrographs showed no tangible precipitation in the as cast samples with reduced grain width and deformation bands but at high temperatures of 150 °C and 200 °C, precipitation was promoted as a result of slipping systems activation. SEM images of the as-cast alloy exhibits dendrites of 250 ± 20 μm in size with η′ phase (MgZn2) precipitates in the inter-dendritic regions. For 150 °C ECAP temperature, a significant refinement was achieved as the passes increased with sub-grain development within the boundary and the precipitate observed has a grain size of 35 ± 15 μm, 25 ± 10 μm, 15 ± 8 μm and 8 ± 6 μm for first, second, third and fourth passes respectively. However, grain sizes of 85 ± 15 μm, 50 ± 10 μm, 30 ± 8 μm and 10 ± 5 μm for first, second, third and fourth passes were observed for 200 °C ECAP temperature. XRD results showed peaks for aluminum and other phases in as-cast condition with precipitates growth in the alloy after the first pass, identified as metastable η′ phase. As the number of ECAP passes increases, η′ peaks moved towards the equilibrium η phase confirming the transformation of η′ phase to stable η phase. The microhardness, Ultimate tensile strength (UTS) and the yield strength of Al–Zn–Mg alloy in different conditions of 150 °C and 200 °C respectively also increased with increase in the number of ECAP passes. This is due to increase in dislocation density, work hardening and grain refinement during ECAP process.

Investigation of microstructure and mechanical properties of Cu-Ni alloy processed by equal channel angular pressing

The Copper-Nickel alloy, C70600, was subjected to severe plastic deformation by the equal channel angular pressing (ECAP) technique. The material was pressed at room temperature along route BC for eight passes. Microstructural analysis and mechanical characterization of the material were done for each of the ECAP pass samples. The initial homogenized material having equiaxial grains of average grain size 75 µm was reduced to 20 µm after eight ECAP passes. Electron backscatter diffraction data presented an increase in low angle grain boundaries with an increase in the number of ECAP passes. Initially, the ultimate tensile strength and the hardness increased by 56% and 94% respectively. After the fifth ECAP pass, a drastic reduction in ultimate tensile strength and ductility was witnessed. Hardness value remained constant after the fifth ECAP pass. Fractography analysis indicate the ductile mode of fracture with reduced dimple size at higher ECAP passes.

Modeling of deformation behavior of copper under equal channel angular pressing

Abstract The deformation behavior of copper during equal channel angular pressing (ECAP) was calculated using a three-dimensional version of a constitutive model based on the dislocation density evolution. Finite element simulations of the variation of the dislocation density and the dislocation cell size with the number of ECAP passes are reported. The calculated stress, strain and cell size are compared with the experimental data for Cu deformed by ECAP in a modified route-C regime. The results of finite element (FE) analysis were found to be in good agreement with the experiments. After a rapid initial decrease down to about 200 nm in the first ECAP pass, the average cell size was found to change little with further passes. Similarly, the strength increased steeply after the first pass, but tended to saturate with further pressings. The FE simulations also showed strain non-uniformities and the dependence of the resulting strength on the location within the workpiece.

Numerical Investigation of Plastic Strain Homogeneity during Equal-Channel Angular Pressing of a Cu-Zr Alloy

A three-dimensional finite element method (3D FEM) simulation was carried out using ABAQUS/Explicit software to simulate multi-pass processing by equal-channel angular pressing (ECAP) of a circular cross-sectional workpiece of a Cu-Zr alloy. The effective plastic strain distribution, the strain homogeneity and the occurrence of a steady-state zone in the workpiece were investigated during ECAP processing for up to eight passes. The simulation results show that a strain inhomogeneity was developed in ECAP after one pass due to the formation of a corner gap in the outer corner of the die. The calculations show that the average effective plastic strain and the degree of homogeneity both increase with the number of ECAP passes. Based on the coefficient of variance, a steady-state zone was identified in the middle section of the ECAP workpiece, and this was numerically evaluated as extending over a length of approximately 40 mm along the longitudinal axis for the Cu-Zr alloy.

On the Effect of ECAP Processing Temperature on the Microstructure, Texture Evolution and Mechanical Properties of Commercial Pure Copper

In this study, the severe plastic deformation (SPD) behavior of commercial-grade pure copper processed using equal channel angular pressing (ECAP) was investigated. The copper rods were processed for up to 4 passes, both at room temperature and 200 oC. The microstructure and texture evolution were studied using a field emission scanning electron microscope (FESEM) equipped with an electron back scattered (EBSD) detector. The effect of ECAP processing on the tensile properties, micro-hardness, and impact toughness was studied. After 1 pass, the average grain size of the rods was determined to be 2.694 and 3.9066 μm at room temperature and 200 oC, respectively. In addition, after 4 passes through ECAP, the strength of the ECAPed samples increased to 381 MPa, and 330 MPa at room temperature and 200 oC, respectively; and the Vickers’ micro-hardness at the peripheral areas increased to 158, and 126, respectively. In the other hand, the experimental findings revealed that the number of ECAP passes has insignificant effect on the impact energy.

Influence of a prior pressurization treatment on creep behaviour of an ultrafine-grained Zr-2.5%Nb alloy

The effect of an application of an external high hydrostatic pressure on creep behaviour, the microstructure, and nanoscale porosity in an ultrafine-grained cladding Zr-2.5 wt%Nb alloy processed by equal channel angular pressing (ECAP) was investigated by comparative creep testing. The results show that, under identical creep loading conditions, ECAP processed specimens subjected to subsequent high hydrostatic pressurization treatment prior to creep exposure exhibited no substantial differences in creep behaviour compared to specimens processed by ECAP only. The selected level of high hydrostatic pressurization treatment used in this study is not indicative of an effective removal of nanoscale porosity resulting from ECAP processing. By comparison to the as-received state, an increasing number of ECAP passes leads to a significant weakening of creep resistence of the alloy. It is suggested that the reasons for the occurrence of creep weakening after ECAP processing are an accumulation of high-angle grain boundaries, multiplication of dislocations, coarsening and/or dissolution of the Nd-rich second phase precipitates, and dislocation/particle interactions.

Microstructure and superplasticity of Mg–2Gd–xZn alloys processed by equal channel angular pressing

Abstract Microstructure, mechanical properties and superplastic behavior of Mg–2Gd–xZn (x = 0, 1, 2 and 3 wt%) alloys were investigated after extrusion and equal channel angular pressing (ECAP). After only 2 passes of ECAP, a homogenous fine-grained microstructure with a grain size of 2.33 μm and a high fraction of high-angle grain boundaries of 84% were formed in the Mg–2Gd–3Zn (GZ23) alloy, while 4 ECAP passes were necessary to create such a structure in the other alloys. This was attributed to the higher solute drag effect in the other alloys, retarding dynamic recrystallization (DRX). Although DRX occurred more easily in the GZ23 alloy, the final DRX grain size was slightly coarser compared to the other alloys. Shear punch testing (SPT) showed that grain refinement during ECAP leads to a slight increase in the shear yield strength of all studied materials after 2 ECAP passes, which was mostly balanced by texture softening caused by the shear texture component and grain growth after 4 ECAP passes. Contrary to the other alloys, the GZ23 alloy exhibited superplastic behavior after a lower number of ECAP passes. In addition, the superplastic temperature for GZ23 was 648 K, which was lower than the 673 K observed for the other alloys. The m-values of ~0.45–0.5 and activation energies of 98–114 kJ/mol suggested grain boundary sliding (GBS) controlled by grain boundary diffusion as the dominant deformation mechanism in the superplastic regime. This was confirmed by microstructural observations.

Enhancing mechanical properties of consolidated nanocrystalline copper powder by means of equal channel angular pressing method

Ultrafine grained and nanostructured materials have drawn significant attention due to their unusual mechanical behavior. The purpose of this research was to study the mechanical properties and microstructural evolution of nanocrystalline copper obtained through a bottom-up procedure of nanoparticle consolidation by equal channel angular pressing (ECAP). ECAP was approved to be a proper approach to produce comparatively big nanocrystalline consolidates including acceptable mechanical properties. The effects of ECAP pass numbers on consolidation achievement were also assessed. The quite large strains observed in the samples were associated with the bimodal distribution condition of grain sizes. The present work reveals that ECAP consolidation of nanoparticles presents a novel opportunity to investigate the mechanical response of nanostructured metals and alloys moreover it gives a chance to the production of unique kinds of bulk materials for useful purposes.

Mechanical behaviour of Aluminium Alloy AA6063 processed through ECAP with optimum die design parameters

ABSTRACT Equal Channel Angular Pressing (ECAP) is one of the most effective techniques for the formation of ultra-fine grained bulk material. The material is passed through the channel in the specially designed die in the ECAP process. The die design parameters like corner angle, channel angle and other parameters play an important role in the formation of ultra-fine grains. The die with optimum design parameters, with channel angle 90° and corner angle 20°, was designed and fabricated in the laboratory and commercial Aluminium AA6063 was used as sample material to investigate the mechanical behaviour/properties before and after the ECAP process. In the present work, the mechanical behaviour of commercially pure Aluminium processed by ECAP die with an optimum die design parameter is studied and examined. The path adopted was BC and pressing was done from 0 to 3 numbers of times. The results revealed that the grain size reduced from 530 to 220 nm and tensile strength increases from 275.8 to 368.4 MPa after three numbers of ECAP passes.

Effect of processing parameters on equal-channel angular pressing of aluminum alloys: An overview

Equal-channel angular pressing (ECAP) is one of the emerging Severe plastic deformation (SDP) technique that makes ultra-fine grains (UFG) microstructure to improve the properties of different materials and composites. The uniqueness of the ECAP technique is that it can refine the grain size without changing the cross-section. Many factors like processing temperature, number of ECAP passes, die channel angle and processing route affects the results obtained from ECAP technique. This review is mainly focused on the mechanical and microstructural properties of aluminium alloys generated after ECAP Process along with number of passes. It is observed as the number of passes increased the hardness and tensile strength of the alloy increase and ductility of the material is reduced. The maximum percentage of grain refining is obtained in the first two or three passes after that no significant changes were observed because the effect of temperature is more than the effect number of passes on the grain size.

Effect of microstructure on the hydrogenation behavior of AZ61 magnesium alloy with silicon carbide and nickel additives, processed by equal channel angular pressing

In this study, AZ61 alloy processed by equal channel angular pressing (ECAP) method, is presented. This research seeks to find out the relationship that exists between the microstructure of the AZ61-magnesium alloy doped with SiC and Ni and processed by ECAP in terms of hydrogen storage properties. The results indicate that grain size reduces nearly 10 times after 4 passes of ECAP. Homogeneous distribution of the SiC in the metal matrix composite (MMC) and dynamic recrystallization are also observed. There is a gradual reduction in the grain size when the number of ECAP passes are increased. This microstructural refinement induced by ECAP improves the storage capacity and reaction kinetics of the alloy. Besides, the addition of Ni catalyst achieves faster absorption and desorption kinetics. However, it does not change its capacity. Ni reacts with Mg to form an intermetallic, which is hydrogen-absorbing, which in turn, catalyzes the reaction. Apart from introducing defects, the ECAP process also produces Mg/Al intermetallic, which acts catalytically. It is shown that SiC-doped AZ61-magnesium alloy can absorb and desorb 6.8 wt% H2 at 648 K and 50 atm.

Changes in the spatial distributions of platelet Al3Ti particles in an Al-Al3Ti alloy by equal-channel angular pressing

Changes in the spatial distributions of platelet Al3Ti particles in an Al-Al3Ti alloy during equal-channel angular pressing (ECAP) were investigated. ECAP was performed under the processing routes of A and Bc up to 8 passes through a die. When applying route A, the Al3Ti particles were greatly fragmented during the ECAP process and also aligned along to the deformation axis, while route Bc resulted in the agglomeration of the Al3Ti particles. The Al3Ti particle size was also found to gradually decrease as the number of ECAP passes was increased. The spatial distributions of these Al3Ti particles in specimens deformed by ECAP were evaluated using the Morisita index, and the results showed that both processing routes generated aggregate distributions, although route Bc produced a homogeneous distribution of Al3Ti particles after 8 passes. These variations in the spatial distributions of the Al3Ti particles can be explained by the occurrence of material flow of the α-Al matrix during ECAP using routes A and Bc.

Tailoring Mechanical Properties of Mg–Al–Zn–Sn–Mn Alloy by Multipass Equal Channel Angular Pressing

Herein, the influence of equal channel angular pressing (ECAP) routes, i.e., A and Bc, on the microstructure and texture evolution of a Mg–3.7Al–0.7Zn–0.8Sn–0.4Mn (wt%) alloy is investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X‐ray diffraction (XRD). It is found that with increasing the number of ECAP passes, the area fraction of the dynamically precipitated secondary‐phase particles increases, whereas particle size becomes larger. After four and six passes of ECAP via route A, shear deformation induced by ECAP promotes the incline of c‐axes toward extrusion direction (ED). The optimum room temperature (RT) mechanical properties (yield strength of ≈225 MPa, ultimate tensile strength of ≈312 MPa, and elongation to fracture of ≈31.9%) are obtained after four passes of ECAP at 200 °C via route A. The improved strength results from fine dynamic recrystallization (DRX)/ed grains, nanoscale secondary‐phase particles, and basal texture. Herein, it is indicated that Mg–Al–Zn–Sn alloys have great potential as low‐cost high‐strength‐ductility wrought Mg alloys.