Equal Channel Angular Pressing Process Research Articles

The effect of thermal and strain-induced aging on the mechanical behavior of room temperature ECAP processing of WE43 magnesium alloy

The WE43 magnesium alloy, in case of improved toughness, can be an appealing material for biomedical applications. The effects of equal-channel angular pressing (ECAP) and post-deformation aging (PDA) on the mechanical behavior of the WE43 alloy were investigated in this study. ECAP of WE43 magnesium alloy at room temperature is extremely challenging because of the insufficient number of slip systems. An optimized core–sheath configuration is proposed, which applies fully compressive stress on the WE43 alloy as the core, resulting in ECAP of the WE43 alloy at room temperature. Unprecedented strain-induced precipitation of both Mg41Nd5 and Mg24Y5 was observed owing to stored mechanical energy and temperature raise in the adiabatic shear bands during ECAP at room temperature. Moreover, the formation of oriented needle-like Mg3(Y, Nd) precipitates and partial recrystallization simultaneously increased the strength to 410 MPa and the strain to fracture to 11.4% after PDA. A combination of bimodal grain size distribution and a high volume fraction of precipitates increased the toughness to 38.96 MJ/m3 after ECAP and PDA.

Correlation of microstructure and bio-tribocorrosion behavior of equal channel angular pressed pure titanium

The effect of equal channel angular pressing (ECAP) strain (i.e., 1st to 4th pass) on the grain size and eventual mechanical and bio-tribocorrosion properties of commercially pure titanium (cp-Ti) has been investigated. Ultra-fine grains (UFG) of 0.8 µm size (from 12 µm) and yield strength enhancement to 785 MPa (from 381 MPa) have been observed for the ECAP 4th pass sample as compared to the annealed condition of cp-Ti. In addition, the maximum hardness increased by 101 HV to 293 HV in the 4th pass samples due to grain refinement caused by the ECAP process. Further, the tribocorrosion behaviour as a function of cp-Ti sample conditions in the simulated body fluid (SBF) has been evaluated. The ultra-fine-grained 4th pass sample shows a lower coefficient of friction (CoF) of ∼0.35 (from ∼0.5) and wear loss due to its enhanced strength than the annealed sample. Moreover, the ECAP 4th pass sample, because of its UFG, exhibits a more negative potential shift (∼0.82 V) as compared to annealed sample (∼0.88 V). However, this shift is marginal due to its low wear scar width and depth, which eventually induced less galvanic coupling effect in it. Abrasion and adhesion are the primary wear mechanisms for all the sample conditions.

Microstructural evolution and superior properties of conductive Al–Fe alloy processed by ECAP

The new conductive Al–Fe alloy (AA8176) is used in power transmission due to its high electrical conductivity. As a non-agе-hardenable alloy, Al–Fe alloy is not a subject for the strength improvement. So, Equal-channel Angular Pressing (ECAP) is introduced to try to develop the advanced Al–Fe alloy with improved mechanical performance and good electrical conductivity. After different number of passes at room temperature, its electrical conductivity is maintained at quite high value (>60% IACS), close to that of pure aluminum, and its change during ECAP processing is insignificant. At the same time, the yield strength increases sharply from 46 MPa to a nearly 200 MPa after 8 passes. Elongation to failure also increases to 11% with increasing the number of passes. Superior combination of strength and electrical conductivity was demonstrated in alloys subjected to ECAP. Also, the study of microstructural evolution with a close attention to the evaluation of grain size, misorientation angle, size and distribution of Al–Fe intermetallic particles was performed. ECAP shows different advantages and potential in Al–Fe alloy performance improvement by achieving the ultra-fined grains and high-density dislocations through the imposed strain, instead of the formation of abundant precipitates in alloys through traditional heat treatment.

Effect of ECAP process on mechanical properties and microstructure of AA-6061 recycled chips

The oxidation of aluminum machined chips makes successful recycling via the traditional re-melting technique difficult. A viable solution to this problem is to utilize solid-state recycling to transform aluminum machined chips directly into semi-finished goods, eliminating the costs of the re-melting process and minimizing CO2 emissions. In the present study, Al-6061 alloy chips have been recycled using hot extrusion followed by severe plastic deformation at ambient temperature to examine the material's mechanical properties and microstructures. The current study investigates the effects of equal channel angular pressing samples after (1, 2, and 4) cycles using a die with 90° and 20° angles, a strain of 1 was applied each pass for a maximum of four cycles at room temperature, through different routes (BC, C) on the mechanical properties of recycled specimens before and after the process. Observations showed a significant improvement in the characteristics of recycled chips exposed to hot extrusion followed by the ECAP technique. Maximum ultimate tensile strength (265, and 238 MPa) maximum yield strength (149, and 136 MPa), and elongation to failure (46 and 41%) for both routes were obtained. Moreover, each pass increases yield strength ultimate tensile strength, and micro-hardness while increasing elongation to failure. The mechanical characteristics of ECAPed specimens were higher than the extruded specimen. The mechanical properties and microstructures of solid-state recycled Al-6061 alloy chip samples were significantly influenced by the number of passes and route types.

Tribological studies on aluminum beryl composites subjected to ECAP process

The strengthening processes of aluminum alloys and their composites are generally assessed after precipitation hardening or following different laid down strain hardening procedures such as Equal Channel Angular Pressing (ECAP), Multi-Axial Forging (MAF), High-Pressure Torsion (HPT), Accumulative Roll Bonding (ARB), etc. Among them, ECAP is considered to be a novel method of producing fine-grained structure with different properties. On-going through the available literature, it is noted that the adoption of ECAP in Aluminum metal matrix composites, especially the Aluminum Beryl composites and then assessing their tribological responses, are scarce to come across. Hence, this particular aspect is addressed in this work.In the present investigation, Al 2024 alloys containing 6% Beryl particles, produced by stir cast route and subjected to ECAP operation up to two passes, have been assessed for slide wear and coefficient of friction (CoF) properties for comparison with un-reinforced Al 2024 alloy for qualitative and quantitative evaluation purposes. The wear and friction evaluation are carried out using the well-known Pin-On-Disc (POD) apparatus for three different loads (49 N, 91 N, and 136 N) and sliding distances (2000, 4000 and 6000 m) at a constant sliding speed of 1.67 m/s.The data reveals that the wear loss decreases with increase in the number of passes due to increase in hardness & decrease in grain size for all the three loads and sliding distances employed. Further, the wear losses show an increasing trend with an increase in the applied load. Also, it is observed that the CoF decreases with increase in number of passes at all loads. It is high in the as cast state and it increases with increase in load. It is inferred from the present findings that the ECAP has made a significant impact on the wear behaviour of Al-Beryl composites, thus emphasizing the fact that the composites are suited for wear resistance applications such as in production engineering sectors.

Effect of ECAP processing temperature on an austenitic TWIP steel's microstructure, texture and mechanical properties

The development of microstructure and texture of twinning-induced plasticity (TWIP) steel sheet during ECAP at two temperatures (250° and 350°) up to four passes were investigated. The high chromium content is the differential of this TWIP steel, a chemical element that reduces the stacking-fault energy and increases corrosion resistance. By imposing ECAP, the volume fraction of twins, dislocation density, and yield strength significantly increase while ductility decreases. This study compared the effect of temperature during applied severe plastic deformation (SPD). Thin parallel slip bands’ high density was observed, and in addition to an intense micro shear, banding took place when pressing was continued by increasing the number of passes. The martensitic transformation was not detected in the deformation-twinning microstructure after more passes. The relationship between the microstructure, strain-hardening behavior, and mechanical properties was investigated after two different deformation schedules of ECAP. The best balance between high strength and good ductility (1915 MPa and 7%) was obtained after four passes at 250 °C and 350 °C. It was found that the quantity of ECAP pass affects the displacement substructure with the formation of shear bands, subgrains, and various variants of twins. These also influenced strain-hardening behavior, microhardness, texture, and ultimate strength.

An Overview on the Effect of Severe Plastic Deformation on the Performance of Magnesium for Biomedical Applications.

There has been a great interest in evaluating the potential of severe plastic deformation (SPD) to improve the performance of magnesium for biological applications. However, different properties and trends, including some contradictions, have been reported. The present study critically reviews the structural features, mechanical properties, corrosion behavior and biological response of magnesium and its alloys processed by SPD, with an emphasis on equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). The unique mechanism of grain refinement in magnesium processed via ECAP causes a large scatter in the final structure, and these microstructural differences can affect the properties and produce difficulties in establishing trends. However, the recent advances in ECAP processing and the increased availability of data from samples produced via HPT clarify that grain refinement can indeed improve the mechanical properties and corrosion resistance without compromising the biological response. It is shown that processing via SPD has great potential for improving the performance of magnesium for biological applications.

Effect of Frictional Contact Surface on Maximum Pressing Load during Equal Channel Angular Pressing Process

Effect of Frictional Contact Surface on Maximum Pressing Load during Equal Channel Angular Pressing Process

Influence of ECAP process on mechanical, corrosion and bacterial properties of Zn-2Ag alloy for wound closure devices

Actual polymeric wound closure devices are not optimal for load-bearing applications due to the low mechanical properties and the risk of inflammation and bacterial infection mainly produced by multifilament and braided configurations. Biodegradable metallic Zn alloys are promising materials candidates; however, mechanical performance, corrosion behaviour, and biological response should be controlled in order to inhibit the risk of inflammation and bacterial infection. To this end, a Zn-2Ag (2 wt% Ag) alloy was processed by ECAP to evaluate the concurrent combined effect of grain refinement and Ag alloying on biodegradation and antibacterial activity. Two ECAP cycles were successfully applied to a Zn-2Ag alloy obtaining a homogeneous ultra-fine-grained structure in which nanoindentation maps suggested isotropic mechanical properties. Lower UTS and YS with higher elongation was reported after ECAP with similar corrosion rates as before processing. ECAP processed samples showed a homogeneous Ag+ release below the minimum inhibitory concentration for S. Aureus and no antibacterial effect was observed by diffusion. As expected, the presence of Ag in Zn-Ag alloys reduced bacterial attachment. Nevertheless, ECAP processed Zn-2Ag provided an excellent antibacterial activity after 3 h probably caused by the uniformly degraded and thus, non– stable, surface observed after bacterial adhesion.

EFFECT OF THE NUMBER OF THE PASSES ON THE MECHANICAL BEHAVIOUR OF ALUMINUM ALLOY PROCESSED USING EQUAL CHANNEL ANGULAR PRESSING (ECAP)

One of the most important industrial processes used in the production of nanomaterials is the ECAP process. Whereby, nanomaterials are produced in relatively large sizes. In this research, the effect of the number of passes on the mechanical behavior of the engineering material was studied. Where the upsetting test was carried out on samples taken from a metal produced by the ECAP process, then the yield stress, maximum stress, and strain values were determined, as well as the Tresca energy fracture criterion was used, and the results were analyzed and converted into graphic relations. From the results, it was found that these values are highly dependent on the number and type of passes.Keywords: ECAP, Aluminum Alloy, Upsetting Test, Mechanical Properties, Anisotropic.

A brief overview of the equal channel angular processing approach

A possible method to create an ultra-fine grain microstructure and enhance the material's characteristics is equal channel angular pressing (ECAP). The number of variables, including the processing route, die angle, number of passes, and operation temperature, are critical in order to analyze the mechanical behaviour and microstructure of the material deformed by the ECAP process. The development of the Mg alloy microstructure and its mechanical characteristics following the ECAP approach have received particular attention. It was found that producing finer microstructure with superior mechanical properties at lower temperatures, more passes, and a smaller die angle is possible. The impact of equal channel angular pressing parameters on the mechanical characteristics and microstructure of Mg alloys is thus briefly summarised in this review paper.

Preparing high-strength and osteogenesis-induced Mg-Gd alloy with ultra-fine microstructure by equal channel angular pressing

Mechanical strength and corrosion resistance are needed for Mg based BMs in the application of biomedical fields. In the present study, a high-strength biodegradable Mg-Gd alloys with an ultrafine microstructure successfully were prepared by equal channel angular pressing (ECAP). The high tensile strength of ECAPed Mg-Gd alloys was attributed to ultrafine DRX grains and fragmented secondary phases. During ECAP, the grain structure was refined by dynamic recrystallization (DRX), and the size of the DRX grains was approximately 300 nm. The secondary phase with lamellar structures was fragmented into fine particles of submicrometer size after ECAP process. As the number of ECAP passes increased, the distribution of the fragmented secondary phase has been changed into a uniform distribution. The corrosion rates calculated from the hydrogen evolution test demonstrated that the 8p-ECAP Mg-Gd alloy with an ultrafine microstructure possessed better corrosion resistance. Cell and osteogenesis induction experiments confirmed that Mg-Gd alloys processed by ECAP exhibited good biocompatibility. This study provides a new method for preparing high-strength Mg alloys with good corrosion resistance and biocompatibility.

Electrochemical behavior of ECAP-processed Sn–5Sb alloy

An attempt has been made in this research to evaluate the effects of severe plastic deformation (SPD) on the electrochemical and passivation response of Sn–5Sb alloy. The electrochemical response of severely deformed alloy through the equal channel angular pressing (ECAP) process has been studied by cyclic voltammetry (CV), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and Mott–Schottky in 0.1 M NaOH solution. The grain structure and corrosion product of samples have been evaluated by X-ray diffraction (XRD), atomic force microscopy (AFM) patterns, transmission electron microscopy (TEM), and field emission scanning electron (FESEM) micrographs. It has been revealed that imposing such a large strain yields specimens with finer grain structure resulting in higher corrosion resistance and higher protecting passive films.

Effect of ECAP die angle and route type on the experimental evolution, crystallographic texture, and mechanical properties of pure magnesium

Abstract In the current study, the effect of equal channel angular pressing parameters such as die route type and die angle were studied. Billets of pure magnesium (Mg) were processed successfully through up to 2-passes of different routes, A, Bc, and C, using equal channel angular pressing dies with different internal angles of 90° and 120° at 225°C. The crystallographic texture and microstructural evolution were investigated using electron back-scatter diffraction. The Vickers microhardness and tensile properties were investigated, analyzed, and linked to the microstructure and crystallographic texture as well. The as-annealed condition revealed relatively coarse equiaxed grains coupled with some extra-elongated grains with average grain size of 6.338 µm. Processing through 2-passes formed an ultrafine grain structure and recrystallized fine grains. This decrease in grain size was associated with hardness and tensile strength enhancement as compared with the as-annealed Mg counterpart. ECAP processing through the 90° die revealed that 2-passes of route Bc was more effective in grain refinement compared to routes A and C, and it reduced the average grain size by 76.45% compared to the as-annealed counterpart. On the other hand, for the ECAP die with 120°, route A was more effective in grain refinement compared to the other routes. Processing through 2-passes of route C resulted in a stronger texture compared to the other routes with momentous rotation for the texture components. Processing of 2-A, 2-Bc, and 2-C through the 90°-die revealed an increase in the Vickers Hardness (HV) of 76.9, 96, and 84.6%, respectively, compared to the AA counterpart. In addition, the tensile findings revealed that the 90°-die resulted in higher ultimate tensile strength coupled with a drop-in ductility compared to the 120°-die. Furthermore, ECAP processing through the 90°-die led to improvement in the ultimate tensile strength by 14.1, 38.4, and 43.75%, respectively, coupled with improving the Mg ductility by 80.9, 73.5, and 47.6% through processing via 2-A, 2-Bc, and 2-C, respectively, compared to the as-annealed counterpart.

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.

Effect of Short-Time Heating after ECAP Processing on Mechanical Properties of 6061 Aluminum Alloy

Effect of Short-Time Heating after ECAP Processing on Mechanical Properties of 6061 Aluminum Alloy

Effect of ECAP processing on microstructure and mechanical behaviour of Ti-6Al-4V manufactured by directed energy deposition

Effect of ECAP processing on microstructure and mechanical behaviour of Ti-6Al-4V manufactured by directed energy deposition

Optimizing the ECAP processing parameters of pure Cu through experimental, finite element, and response surface approaches

Abstract The main aim of the current work is to investigate the effect of equal channel angular pressing (ECAP) processing parameters, namely, number of passes, ECAP die angle, route type, and processing temperature on the mechanical and electrical properties of pure copper (Cu). The finite element method was used to simulate the homogeneity of stress and plastic strain distribution during ECAP processing. The response surface methodology (RSM) was used to identify the optimum ECAP processing parameters by analyzing the impact of ECAP conditions on responses. A second-order regression model and analysis of variance were created to analyze the ECAP condition of optimum responses. A genetic algorithm (GA) was also applied to optimize the ECAP condition. Finally, a hybrid RSM–GA was created to improve the optimization of ECAP responses and corresponding conditions evaluated using GA. The developed models were validated and compared with the experimental findings to prove that they are reliable as predictive tools. The optimization findings revealed that route Bc was more effective in improving the hardness, yield stress, ductility, and impact energy whereas route A was more effective in improving the ultimate tensile strength and the electrical conductivity of the Cu billets. Furthermore, the optimum die angle, number of passes, and processing temperature for the mechanical and electrical properties were also identified individually.

Effect of ECAP process on deformability, microstructure and conductivity of CuCoNi alloy

The study deals with the influence of various variants of severe plastic deformation in the Equal Channel Angular Pressing (ECAP) process on the microstructure, microhardness, and conductivity of CuCoNi alloy. The microstructure evolution was studied by microscopic observations and electron back-scattered diffraction (EBSD) in a scanning electron microscope (SEM). The Vickers method was used to test the microhardness of the samples after various variants of the ECAP process. The conductivity was measured with an eddy current electrical conductivity meter based on the complex impedance of the probe. The results indicated the possibility of deformation of CuCoNi alloys in the process of pressing through the ECAP angular channel and developing their microstructure and properties. The method is an effective tool for strengthening the tested copper alloy by refining its microstructure. After the first pass, the grain size was reduced by 80%. Increasing the plastic deformation temperature did not significantly affect the obtained level of microstructure fragmentation - the average grain size is approx. 1.4-1.5 ?m. The fragmentation of the microstructure had a negligible effect on the conductivity of the CuCoNi alloy, which oscillated at the value of 13 MS/m after the ECAP process.

MECHANICAL PROPERTIES OF SINTERED AL-SN-FE ALLOYS

Plastic flow under compression was studied in samples of Al-Sn-Fe alloys produced by sintering from elemental powder mixtures. Some of the sintered composites were additionally compacted at 250°C in a closed mold at a pressure of 300 MPa, and some were processed via equal-channel angular pressing using route A (ECAP-A) at the same temperature. A key structural feature of the sintered alloys is the presence of agglomerates of solid Al3Fe particles cemented with tin, formed in place of iron powder particles as a result of interaction between Al and Fe during sintering. The agglomerates have high strength but are sufficiently ductile owing to tin. They do not break during deformation and effectively suppress the propagation of localized flow bands and microcracks. In compression tests of three-phase Al-20Sn-17Al3Fe composite samples, the particle agglomerates retained their shape and moved as solid structures, while the samples showed good ductility during testing. In ECAP processing via route A, the agglomerates were pulled in the direction of material flow, which negatively affected their ductility in subsequent compression tests.