Equal Channel Angular Pressing Research Articles

Achieving an Optimal Balance of Strength and Elongation in AA 1050 Aluminum Alloy via Equal Channel Angular Pressing, Intermediate Annealing, and Post-Rolling

Achieving an Optimal Balance of Strength and Elongation in AA 1050 Aluminum Alloy via Equal Channel Angular Pressing, Intermediate Annealing, and Post-Rolling

Influence of ECAPressing temperature on crystallinity and mechanical behaviour of polypropylene and high-density polyethylene / Influência da temperatura de ECAPressing na cristalinidade e comportamento mecânico do polipropileno e do polietileno de alta densidade

In this paper, the influence of single equal channel angular pressing, ECAPressing, pass and processing temperature on crystallinity evolution and mechanical behaviour of the polymers polypropylene, PP, and high-density polyethylene, HDPE was investigated. ECAPressing tests were performed at the temperatures of 25, 50, 75 and 100°C for HPDE and 25, 90 and 120ºC for PP. The materials mechanical behaviour before and after ECAPressing tests was evaluated from room temperature compression tests while their crystallinity changings were analyzed through differential scanning calorimetry, DSC, experiments. In terms of strengthening and by comparison with as-received materials, it was observed an interesting efficiency of ECAPressing performed at 100°C for HDPE and 120°C for PP. In relation to crystallinity evolution, the results obtained from DSC tests showed its considerable increasing for higher pressing temperatures also by comparing either to as-received conditions or after single pass of equal channel angular pressing at room temperature.

Enhanced corrosion behavior of ultrafine-grained pure titanium in simulated high-temperature seawater

Corrosion behavior of ultrafine-grained (UFG) pure titanium was studied in simulated seawater at high temperature to increase the probability for marine devices. The UFG Ti was prepared by equal channel angular pressing. The grain size was around 450 nm. The results showed that the corrosion current density of UFG Ti was lower than coarse-grained (CG) Ti in 3.5%NaCl solution at 80 °C, and the UFG Ti could resist pitting corrosion preferably. The basal texture of UFG Ti was stronger and the content fraction of TiO2 in the passive film was higher than CG Ti. The enhanced corrosion performance of UFG Ti at high temperature was attributed to the comprehensive impact of grain size, texture and passive film.

Ultrafast severe plastic deformation in high-entropy alloy [formula omitted] via dynamic equal channel angular pressing

An extensively investigated high-entropy alloy (HEA), Al0.1CoCrFeNi, is processed by dynamic equal channel angular pressing (D-ECAP) and subsequent annealing. Severe shear deformation and ultrahigh strain rate give rise to simultaneous activation of the {111}〈112〉 macro deformation twins and kink bands with the 〈110〉 or 〈112〉 rotation axes. Secondary kink bands are also observed in primary kink bands. With increasing annealing temperature, the deformation twins and kink bands both become less or disappear. The yield strength is increased by ∼255% solely by D-ECAP compared to the as-cast HEA. A reasonable combination of high strength and good ductility is achieved through annealing twins in recrystallized grains via annealing the D-ECAP-processed alloy at 900 °C. It is the first observation on kink bands within a face-centered cubic HEA under various loading conditions. The strengthening in these D-ECAP-processed samples before and after annealing is discussed in terms of grain boundary strengthening and dislocation strengthening.

Effect of rapid cooling on the microstructure and properties of fine-grained 7075 aluminium alloy under friction stir welding

In this study, 7075 aluminium alloy plates with a fine-grained structure were produced by four-pass equal-channel angular pressing and subsequently joined at room temperature (297 K) using carbon dioxide (CO2)-assisted cooling friction stir welding. Electron backscatter diffraction, x-ray diffraction, Thermocouple measuring instrument,optical microscopy and microhardness testing were used to investigate the microstructural and mechanical characteristics of friction stir welded joints. The results indicated that the maximum temperatures of welded joints at room temperature and CO2-assisted were 673 K and 568 K, macroscopic surfaces of the welded joints under CO2-assisted cooling were smoother than those created under room temperature; this was because the rapid cooling of liquid CO2 inhibited the growth of grains and, following dynamic recrystallisation, the grain size was finer (∼2.9 μm). Compared with the fine-grained base material (BM), the proportion of large-angle grain boundaries in the stir zone region of the welded joints increased under both conditions, and the anisotropy was weakened. The precipitation hardening of the joints was obvious; the welded joints appeared to soften at room temperature, while the hardness of the joints was the same as that of the fine-grained BM under the CO2-assisted cooling condition.

A comparative study on the microstructural features and mechanical properties of an Mg–Zn alloy processed by ECAP and SSE

The influence of the equal channel angular pressing (ECAP) and simple shear extrusion (SSE) processes on the microstructural and textural developments, as well as mechanical properties of Mg–4Zn alloy was studied. Application of 1, 2, and 4 passes of ECAP and SSE resulted in remarkable grain refinement of the initial microstructure of extruded material. Due to the greater shear strain and finer second phase particles, acting as obstacles to grain growth, smaller grain sizes were developed in the SSEed samples compared to the ECAPed counterparts. The fiber texture component of the extruded alloy was gradually transformed to a shear texture component after 4 ECAP passes, while 1, 2, and 4 passes of SSE produced a semi-fiber texture, in which basal planes were parallel to the longitudinal axis of the processed sample. Due to the applied reversal shear strain to the sample inside the SSE die, the volume fraction of the dynamically recrystallized (DRXed) regions was lower than that in the ECAP process which exerted a one-step shear strain to the sample. Shear punch test (SPT) results indicated that both ECAP and SSE improved the strength of the extruded alloy due to the grain boundary strengthening, texture hardening, and dislocation-dislocation interaction mechanisms. The strength of the SSEed samples was greater than ECAPed specimens, due to the finer grain size, higher volume fraction of un-DRXed grains, and lower Schmid factor of the semi-fiber texture component of the former.

Effect of processing route on grain refinement and mechanical properties in equal channel angular pressing of aluminium alloy AA7068

Influence of different processing routes on microstructure of aluminum alloy AA7068 during equal channel angular pressing (ECAP) up to four passes is investigated. Equalchannel angular pressing is one of the best severe plastic deformation methods to achieve ultra-fine grain structure by subjecting metal to an intense plastic strain through a simple shear. A significant amount of grain refinement as occurred by passing aluminium alloy samples through ECAP split die at 200°C temperature from first pass up to four passes with two different processing routes such as route A and route Bc. The experimental results revealed that out of two different processing routes, route Bc where the samples are rotated by an angle of 90° in the same direction after each pass, is able to achieve rapid microstructure evolution with a better grain refinement and an equiaxed microstructure as compared to that of route A. Mechanical properties such as hardness and tensile strengths of the ECAP processed samples via route A and route Bc are also revealed that route Bc is the optimum process parameter which induces better mechanical properties into the metal.

Optimization of processing conditions in equal channel angular pressing for superior structure and properties

In the past 25 years, much interest has been paid to the production of ultrafine-grained (UFG) materials due to their superior structure and properties. Equal channel angular extrusion or pressing (ECAE or ECAP) is one of the severe plastic deformation (SPD) technique used to produce UFG materials. Compared to other SPD process, higher strain per pass and higher total productive strain after ‘n’ number of passes is possible in this technique. ECAP process is affected by various processing conditions or parameters. These processing conditions mainly affects the structure and properties produced through this technique. In this article, an effort has been made to provide the effect of each processing parameter on the structure and properties developed through this technique. Various processing conditions like- processing route, channel angle, outer arc of curvature, pressing speed, load and friction, processing temperature and application of back-pressure are critically discussed and effect of these parameters are summarized.

Microstructure Evolution and Properties of β-TCP/Mg-Zn-Ca Biocomposite Processed by Hot Extrusion Combined with Multi-Pass ECAP

To further improve the comprehensive performance of Mg-based alloy, hot extrusion combined with multi-pass equal channel angular pressing (ECAP) was applied to process Mg-3 wt%Zn-0.2 wt%Ca alloy and 1 wt%β-TCP/Mg-3 wt%Zn-0.2 wt%Ca biocomposites. The microstructure evolution, mechanical properties, corrosion behavior, and cell biocompatibility of the experimental specimens were systematically investigated. The average grain size of 13.4 ± 0.6 μm in MgZnCa alloy and 9.6 ± 0.3 μm in composites materials can be achieved by six ECAP passes. The uniaxial compressive strength (UCS) of 388.4 ± 7.3 MPa and the strain at failure of 14.3 ± 1.5% were confirmed in MgZnCa alloy, while the UCS of 405.3 ± 7.4 MPa and the strain at failure of 9.8 ± 1.9% were achieved by the addition of β-TCP after six ECAP passes. In spite of different compositions, the minimum corrosion rate of 0.895 mm·Y−1 and 1.117 mm·Y−1 can be achieved by two ECAP passes at 593 K. The cytocompatibility evaluation revealed that the experimental materials processed by six ECAP passes had no significant cytotoxicity to L929 cells, and the addition of β-TCP improved the cytocompatibility.

Corrosion behaviour improvement from the ultrafine-grained Al–Zn–In​ alloys in Al–air battery

Corrosion of aluminium anode in alkaline solution is a challenging matter for the development of a long-life aluminium anode in Al–air battery. This research focuses on grain size reduction by equal channel angular pressing (ECAP) of Al, Al–Zn, and Al–Zn–In samples. The average grain size of all samples after ECAP is lower than 1μm. Open circuit potential, potentiodynamic polarisation, electrochemical impedance spectroscopy, and self-corrosion test were carried out to study the effects of alloying elements (Zn, In) and grain size reduction by ECAP on the electrochemical behaviours of aluminium alloy anodes. The results show that alloying element, zinc, can improve the stability of ion dissolution by porous Al2ZnO4 film formation. Indium can activate ion dissolution that causes enhanced electrochemical activities for Al–Zn–In sample. Moreover, increasing grain boundaries through grain size reduction can enhance more negative potential and cause a uniformly corroded surface of Al–Zn–In sample, leading to a longer anode life in alkaline solution.

Effect of severe plastic deformation on the precipitation kinetics and the properties of CuCoNiBe alloys

The effect of the precipitation hardening by means of the conventional heat treatment and the combined thermomechanical treatment (i.e., equal channel angular pressing (ECAP) with subsequent aging) on the electrical conductivity, mechanical properties and precipitation kinetics of precipitation hardening, quadruple CuCo1Ni1Be alloy was investigated. No experimental studies on the effect of ECAP on the electrical conductivity and precipitation kinetics of CuCoNiBe alloys have been reported. Systematic microstructural and mechanical investigations show that both ECAP processing and post-ECAP aging result in a significant increase in the hardness and strength of the alloy due to the grain boundary strengthening by means of the grain refinement (and the formation of subgrains) and due to the precipitation hardening by means of the formed precipitates (primary and secondary beryllides) in the fine-grained structure, respectively. Moreover, the electrical conductivity of both solution treated and ECAPed alloys increases with increasing aging time due to the precipitation of the solute atoms in α-Cu matrix leading to decreasing electrical resistivity. However, the CuCo1Ni1Be alloys subjected to ECAP exhibit a lower conductivity than the solution treated ones, which can be attributed to an increase in resistivity caused by increased probability of electrons scattering by severe plastic deformation. The linear relationship between electrical conductivity and volume fraction of the precipitates according to the Martition's law and the empirical Avrami equation are used to investigate the precipitation kinetics of the CuCo1Ni1Be alloy. The S-shaped volume fraction of precipitates vs. aging time curves clearly indicate that the precipitation kinetics of the CuCoNiBe alloys can be significantly promoted by ECAP processing. The results of the present study provide new insights into the interaction of the severe plastic deformation, the kinetics of precipitation, and the microstructural, mechanical and physical properties of the CuCo1Ni1Be alloy.

A Review on Effect of Stress and Strain Distribution on the AA5083 With Respect to Different Channel Angle of ECAP

The focus of this study was on the effect of channel angle on stress distribution in the material aluminum alloy 5083. The mechanical properties of a mate- rial are related to the grain size. Equal channel angular pressing (ECAP) is a method for deforming materials in such a way that a strong mechanical prop- erties material is formed while the dimensions of the work piece stay fixed in order to make ultra-fine-grained materials. One of the parameters of ECAP is the channel angle. It’s crucial to understand the impact of a die channel angle on material stress distribution before designing one. When the work piece passes through the channel angle, the die channel angle is built differently to see the effect of stress distribution. At the place where the die’s channels angle intersected, the grain structure was evaluated. The result of the influence of die channel angle on stress distribution is shown in this study’s analysis. It is well established that the channel angle has an impact on mechanical behaviour. The inhomogeneity index (Ci)and standard deviation (S.D.) are two approaches for assessing strain homogeneity. Ciis demonstrated to be an ineffective tool for analysing strain distribution homogeneity. Furthermore, it is advised that constructing Equal Channel Angular Pressing die geometry to obtain the best strain circulation homogeneity rather also the best efficient strain consequence is preferable.

Evolution of Microstructure, Texture and Corrosion Properties of Additively Manufactured AlSi10Mg Alloy Subjected to Equal Channel Angular Pressing (ECAP)

In the selective laser melting process (SLM), the region irradiated by the laser beam is melted and quickly solidified, forming solidification lines (laser scan tracks) with symmetrical shapes. Because of the unique (rapid) crystallization conditions, the subgrain structures, typically observed inside these solidification lines, could also have variable geometric symmetrical patterns, e.g., cellular, pentagonal, or hexagonal cellular. The existence of such distinctive microstructures in SLM-made alloys has a significant impact on their superior mechanical and corrosion properties. Thus, any modification of this symmetrical microstructure (due to post-processing) can degrade or improve the properties of SLM-fabricated alloys. This study presents the experimental results on the effects of heat treatment and ECAP on microstructure modification and corrosion behavior of SLM-fabricated AlSi10Mg alloy. Light microscopy, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD) were used for microstructural analysis. The corrosion properties of the given samples were determined using open-circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. EBSD observations showed that the imposed strain resulted in an obvious reduction in grain size to ~1.42 µm and ~0.24 µm after the first and second ECAP passes, respectively. Electrochemical tests revealed that the corrosion resistance of the ECAP-processed AlSi10Mg alloy improved significantly, which was confirmed by a nobler Ecorr and lower Icorr values, and higher polarization resistance. The final results indicated that the strain-induced crystalline defects provided more nucleation sites for the formation of a denser and thicker oxide film, thus enhancing the corrosion resistance of the AlSi10Mg alloy.

Tailoring the microstructure and texture to achieve high strength in a high-Al content Mg alloy by stepless-temperature-reduction ECAP

A stepless-temperature-reduction equal channel angular pressing (ECAP) approach showing a good advantage over the customary one (i.e., isothermal ECAP) in microstructure refining and texture modifying of Mg–Al binary alloy was proposed. The average grain size of Mg–13Al (wt.%) alloy processed by this new approach is substantially refined down to 790 nm, accompanying with the presence of high-density dynamically precipitated β phase particles whose average size is approximately 219 nm. Moreover, a strong “hard” preferred orientation is developed after processing, namely, an appreciable portion of the grains have their c-axes tilted by about 81° with respect to the extrusion direction. Eventually, the ultrafine grain structure and “hard” crystallographic orientation confer the Mg–13Al alloy with a high tensile yield strength of 367 MPa. The novel ECAP approach given here can apply to other Mg alloys wherein precipitation strengthening is insignificant.

Intrinsic heterogeneity of grain boundary states in ultrafine-grained Ni: A cross-scale study by SIMS and radiotracer analyses

Using a correlated diffusion study applying secondary-ion mass spectroscopy (SIMS) and radiotracer analyses, the co-existence of both relaxed and deformation-modified non-relaxed high-angle grain boundaries (GBs) in ultrafine-grained Ni of 2N6 purity processed by equal channel angular pressing (ECAP) is clearly revealed. Due to different depth and lateral resolutions and using experimentally accessible diffusion times, SIMS provides a direct access to the properties of relaxed “slow” GBs (at short penetration depths) while the radiotracer measurements reveal simultaneously the contribution of the deformation-modified “fast” GBs (at large penetration depths). The temperature stability of ultrafine-grained structure of 2N6 Ni is investigated using electron back-scatter diffraction after annealing treatments corresponding to the diffusion experiments. No changes of the ECAP-produced microstructure occur at 403 K, while the ultrafine-grained structure is remarkably evolving to a coarse-grained one at 603 K. The knowledge of the microstructure evolution is used to quantify the diffusion data. The combination of the two complementary techniques allows not only to perform a cross-scale analysis of the mass transport, but also to probe consistently the existence and kinetic properties of different multi-level hierarchic microstructure features. Therefore, the results obtained is a step forward a better understanding of the physics of ultra-fine-grained materials (UFG). For the first time in the case of UFG materials, the SIMS technique is used in a mode with lateral resolution which is correlated with the microstructure characteristics resolving a multi-level hierarchy of diffusion properties of short circuits in severe plastically deformed materials.

Research of forming and sintering processes of copper powder blanks for equal channel angular pressing

Copper-based powder materials have found their application in many industries. These include classical powder metallurgy, automotive and aviation industries, microelectronics, instrument engineering, and nanotechnology. In this paper, the processes of forming and sintering copper powders obtained by various methods are considered. The main part of the research was carried out on powders of the PMS-1 brand obtained by electrolysis. Four batches of samples (18 pieces each) were pressed at different pressures. Based on the results of the research, a molding mode was proposed, which should ensure the density of blanks not less than 70 % of the density of compact material. To find the simplest and most rational modes of sintering blanks, the process was carried out in air and in dissociated ammonia. The parameters of the samples were calculated after each technological operation, and the volume shrinkage of the samples was calculated depending on the initial density. Draft tests were carried out. Sediment tests were performed up to a maximum pressure of 400 MPa. Despite the fact that the degree of high-altitude deformation was 37–40 %, none of the samples collapsed during the tests, and no visible cracks were observed. Based on preliminary experiments, the masses and forming modes of rectangular blanks that were used for equal channel angular pressing were calculated. Equal channel angular pressing was performed for two samples parties obtained using different sintering modes. When pressing the first samples party, the lack of the required level of back pressure led to either a complete or significant violation of the material integrity. Before pressing the samples of the second party, a copper sample was previously placed into the channel to create a natural backpressure. It was also possible in principle to carry out the process of equal channel angular pressing of porous sintered workpieces without violating the integrity of the material.

Equal channel angular pressing die design through finite element analysis method for non-strain hardening material

ABSTRACT The present research aimed to optimise process parameters such as outer corner angle (ψ = 0°–36°), frictional coefficient (μ = 0–0.05), inner corner angle (ω = 0°–8°) and die channel angle (φ = 90°–120°) for the equal channel angular pressing (ECAP) die design considering a non-strain hardening material Al6061-T6 alloy using ABAQUS finite element analysis software in terms material flowability, corner gap formation, surface gap formation, induced strain intensity and strain distribution. The ECAP die having 100° φ, 24° ψ, 0.02 μ and 8° ω provide better material flowability, (no corner gap formation and surface gap formation), moderate induced strain intensity and homogeneous distribution. The ECAP processing on the designed die effectively modifies the microstructure morphology of as-cast Al6061 alloy. The α-Al grain size decreases and roundness increases and the thicker grain boundary is altered into the thinner boundary, as an effect of this, hardness and tensile strength improved by 28.3% and 32.7%, respectively.

Assessment of Severe Plastic Deformation Processes in Bulk and Nanostructured Metallic Glass

The metallic glasses are known as amorphous and metastable materials. These materials have superior mechanical properties over crystalline materials with the same chemistry. Continuous efforts were made to improve the properties of metallic glass. The severe plastic deformation (SPD) method is used to improve the ductility of the glass. SPD causes the deformation at the atomic level in the disordered structure of the glass. Many methods are reported, such as cryogenic cycling, high-pressure torsion, and equal channel angular pressing, which are used for the SPD. In recent works on nanostructured metallic glasses, it has been evidenced that some properties, for example, mechanical, thermal, and magnetic, have improved compared to the bulk metallic glass. This paper has reviewed the recent progress in the SPD of the bulk and nanostructured metallic glasses. Different methods for the SPD have been addressed here. The effect of SPD on the properties of metallic glass is deliberated in this paper. Moreover, the challenging tasks of deformation occurrence in the glass and its characterization were considered, trying to develop a sound understanding of SPD in bulk and nanostructured metallic glasses.

THE EFFECT OF PRECIPITATION ON MICROSTRUCTURE AND CORROSION BEHAVIOUR OF ZK60 SUBJECTED TO SEVERE PLASTIC DEFORMATION AS BIODEGRADABLE MATERIAL

Microstructure and corrosion behaviour of ZK60 subjected to severe plastic deformation (SPD) as biodegradable material has been investigated in terms of grain refinement process and precipitation formation. Equal channel angular pressing (ECAP) was one of the well-known SPD techniques due to their advantages to promote dislocation and grain fragmentation. ZK60 billet was cut to a 10 mm diameter cylindrical shape for biodegradable material application. ECAP process was carried out up to two passes by Route Bc at 423 K temperature process. Microhardness test was performed at ECAP processed sample, and the structure observation was carried by optical microscope and transmission electron microscope. The corrosion behaviour of the material was investigated by an anodic polarization curve. The ECAP process promotes dislocation accumulation efficiently and ultrafine-grained structure formation. It may improve the formability characteristic of ZK60. The hardness also showed significant increment during the ECAP process due to the high level of deformation. Corrosion behaviours and microstructure observation during the ECAP process showed a correlation that concluded that grain refinement and precipitation formation influenced the electrochemical properties. The alloying element such as Zn and Zr promoted the protective film for corrosion due to their ability for pitting protection. ECAP improved the precipitation formation for corrosion resistance, microstructure uniformity and material formability.

Superplastic‐Like Behavior and Enhanced Strength of a Two‐Phase Titanium Alloy with Ultrafine Grains

Here, the two‐phase titanium alloy Ti‐5.7Al‐3.8Mo‐1.2Zr‐1.3Sn (Russian name VT8M‐1) with an ultrafine‐grained (UFG) structure is successfully produced by equal‐channel angular pressing (ECAP). This UFG alloy demonstrates a significant increase in strength at room temperature (RT) and superplastic‐like behavior during compression at elevated temperatures in a range of 650–800 °C. This unusual behavior is used in this work to study the forging of the alloy at 700 °C, which simulates the process of making an aircraft engine blade. It is shown that after this forging the alloy has significantly higher strength properties than after standard processing. The origin of such superior behavior of this UFG alloy is discussed.