Equal Channel Angular Pressing Process Research Articles

An investigation of microstructure and mechanical properties of as-cast Zn–22Al alloy during homogenizing and equal channel angular pressing

In this study, the effect of homogenization heat treatment and equal channel angular pressing process (ECAP) on microstructure and mechanical properties were explored in Zn–22Al alloy. It was observed that homogenization caused a significant part of the structure to transform to equiaxed grains from an initially lamellar structure. Also, with increasing time of homogenization, a homogeneous structure with no coarse phases were created. Average grain sizes of 48, 2.5, 1.2 and 1.1 μm were respectively achieved after homogenization for 4, 8, 12 and 24 h at 375 °C followed by water quenching. By removal of the lamellar structure during homogenization, improved superplastic behavior was observed. By increasing the time of homogenization, a decrease in microhardness took place which can be due to the loss of hard dendritic phases in the microstructure. On the other hand, grain size of 0.44 μm was achieved after 8 passes of ambient temperature ECAP process which was found to be quite effective in forming the ultra-fine grained (UFG) and equiaxed microstructure leading to further improvement in superplastic behavior. By increasing the number of ECAP passes, the failure elongation increased. On the other hand, the microhardness curve showed a work softening which is associated with the dynamic recovery/recrystallization of η phase after ECAP process.

Investigation of the Effect of ECAP Parameters on Hardness, Tensile Properties, Impact Toughness, and Electrical Conductivity of Pure Cu through Machine Learning Predictive Models.

Copper and its related alloys are frequently adopted in contemporary industry due to their outstanding properties, which include mechanical, electrical, and electronic applications. Equal channel angular pressing (ECAP) is a novel method for producing ultrafine-grained or nanomaterials. Modeling material design processes provides exceptionally efficient techniques for minimizing the efforts and time spent on experimental work to manufacture Cu or its associated alloys through the ECAP process. Although there have been various physical-based models, they are frequently coupled with several restrictions and still require significant time and effort to calibrate and enhance their accuracies. Machine learning (ML) techniques that rely primarily on data-driven models are a viable alternative modeling approach that has recently achieved breakthrough achievements. Several ML algorithms were used in the modeling training and testing phases of this work to imitate the influence of ECAP processing parameters on the mechanical and electrical characteristics of pure Cu, including the number of passes (N), ECAP die angle (φ), processing temperature, and route type. Several experiments were conducted on pure commercial Cu while altering the ECAP processing parameters settings. Linear regression, regression trees, ensembles of regression trees, the Gaussian process, support vector regression, and artificial neural networks are the ML algorithms used in this study. Model predictive performance was assessed using metrics such as root-mean-squared errors and R2 scores. The methodologies presented here demonstrated that they could be effectively used to reduce experimental effort and time by reducing the number of experiments runs required to optimize the material attributes aimed at modeling the ECAP conditions for the following performance characteristics: impact toughness (IT), electrical conductivity (EC), hardness, and tensile characteristics of yield strength (σy), ultimate tensile strength (σu), and ductility (Du).

The Effect of Rotary-Die Equal-Channel Angular Pressing Process on the Microstructure, the Mechanical and Friction Properties of GW103 Alloy.

In this study, the effect of rotary-die equal-channel angular pressing (RD-ECAP) on the microstructure and texture evolution of GW103 alloy is studied. RD-ECAP processes were carried out for 1, 4 and 12 passes at 450 °C. The mechanical properties and friction behavior of RD-ECAP-processed Mg-10Gd-3Y (wt%) alloy (GW103) are discussed. The results reveal that the size of dynamic recrystallized grains and second-phase particles are significantly refined to about 1.3 μm and 1 μm, respectively. The texture evolution of the processed samples is studied by X-ray diffraction and electron backscattered diffraction techniques. The multiple texture components formed are not observed after the conventional ECAP process. Moreover, different dynamic recrystallization (DRX) mechanisms are systemically analyzed and discussed in view of the texture evolution of ECAP processed samples. The final textures obtained after 12 passes are identified as two types: The C-texture type induced by continuous and discontinuous DRX, and the random texture components induced by reorientation of the initial <101¯0> fiber. Based on the grain refinement, precipitate strengthening and texture weakening mechanisms, a high-performance ternary alloy of Mg-Gd-Y was firstly obtained through 12 passes RD-ECAP processing, with a combination of high yield strength of 312 MPa and a high ductility of 22%. In addition, the friction behaviors are also studied. The multi-pass-processed samples exhibit a relatively lower friction coefficient under a load of 10 N at room temperature.

Regulating mechanical properties and degradation behavior of biodegradable Zn–0.6Mg alloy via ECAP plus cold rolling

Binary Zn–Mg alloys have great potential as biodegradable implants due to their good biological safety and moderate degradation rates. Herein, a new combined process of ECAP plus cold rolling of as-cast Zn–0.6Mg alloy was developed to address its application problem of insufficient mechanical properties and serious localized corrosion. Cold rolling process can break the eutectic phase and refine grains, while deformed grains were dominant with a lot of dislocations. 8-pass ECAP process can refine grains by recrystallization, and the grains were equiaxed with less dislocations. The strength and ductility were greatly improved after cold rolling (CR) or ECAP processing compared with that of as-cast alloy, but the strength still cannot meet the requirement of orthopedic implant materials. After 8-pass ECAP+CR75% (ER) processing, the strength was further improved, which benefited from fine grain strengthening, second phase strengthening, and strain strengthening mechanisms. Tensile yield strength (σYS), ultimate tensile strength (σUTS), and fractured elongation of ER alloy were 301.2 MPa, 411.8 MPa, and 28.5%, respectively, which can meet the requirement of orthopedic implants. The eutectic phase fragmentation and grain refinement caused by cold rolling and ECAP process can reduce the galvanic corrosion tendency of the Zn–0.6Mg alloy. The corrosion resistance was further improved after 8-pass ECAP+CR75% processing with the degradation rate of 0.025 mm/y, and the alloy tended to corrode uniformly.

Development of a magnesium based multicomponent alloy with low density and high ductility

Driven by the concept of high entropy alloy, Mg62.9Li30Al3Y1.3Gd1.5Sc1.3 (at. %), a new multicomponent alloy is designed to solve the brittleness of lightweight high entropy alloys (LWHEAs). The microstructure and mechanical properties are also studied. As cast, the alloy consists of bcc solid solution phase with a large number of second phases and stands out for the low density (1.62 g/cm3) and the high compression strain (>45 %). Then two typical deformation processes, cold rolling and equal channel angular pressing (ECAP), were applied to improve the strength. After cold rolling, the ultimate tensile strength improved from 107 MPa to 145 MPa and the ductility increased by two times; After ECAP processing, the ultimate tensile strength considerably increased to 211 MPa without ductility loss.

Solid state recycling of Mg–Gd–Y–Zn–Zr alloy chips by isothermal sintering and equal channel angular pressing

The Mg-7Gd-4Y-2Zn-0.5Zr alloy chips were successfully recycled through isothermal sintering and equal channel angular pressing (ECAP). The mechanical properties and microstructure evolution of samples during the recycling process were studied in detail. The eutectic phases in the as-cast alloy transform into long period-stacking ordered (LPSO) phases after homogenization, which can improve the plasticity of the material. After isothermal sintering, the density of the sample is lower than that of the homogenized sample, and oxide films are formed adjacent to the bonding interface of the metal chips. Hence, the plasticity of the sintered sample is poor. Dense samples are fabricated after ECAP. Although the grains are not refined compared to the sintered sample, the microstructure becomes more uniform due to recrystallization. Fiber interdendritic LPSO phase and kinked 14H-LPSO phase are formed in the alloy due to the shear deformation during the ECAP process, which improves the strength and plasticity of the sample significantly. Furthermore, the basal texture is weakened due to the Bc route of the ECAP process, which can increase the Schmid factor of the basal slip system and improve the elongation of the sample. After 2 ECAP passes, the fully densified recycled billet shows superior mechanical properties with an ultimate tensile strength of 307.1 MPa and elongation of 11.1%.

Microstructure evolution and wear properties of ECAP-treated Al-Zn-Mg alloy: Effect of route, temperature and number of passes

In this study, the effect of severe plastic deformation on Al-Zn-Mg alloy was investigated by ECAP method. The ECAP process parameters were determined using Taguchi experimental design for different routes (A, B C and C), different temperatures (100, 150 and 200 °C) and different number of passes (2, 4 and 8). EBSD and TEM analysis were used for microstructural characterization of the samples and the dry sliding wear test was used to measure the mechanical strength. In the study of microstructural properties, it was determined that there was a direct relationship between the number of passes and temperature. With the increase in the number of passes and the decrease in the temperature, a severe decrease in grain size in the samples was observed. It was observed that the sample subjected to ECAP treatment with 8 passes at 100 °C in the B C route was microstructurally coaxial and had the smallest grain size, and the same sample showed the best wear properties.

Corrosion-fatigue resistance of ultrafine grain commercially pure titanium in simulated body fluid

Commercially pure titanium (CP-Ti) due to excellent biocompatibility and high specific strength is known as a metallic biomaterial and is widely utilized in medical applications as implant material. Because of low strength of CP-Ti as compared to other bio-metals, it has been proved in literatures that applying equal channel angular pressing (ECAP) process can be useful to enhancement of mechanical and metallurgical properties of CP-Ti by improvement of initial microstructure to ultrafine grained (UFG). Implant in human body is attacked from cyclic fatigue loads and corrosion, simultaneous. Hence, aim of this study is examination of corrosion-fatigue resistance of CP-Ti before and after introducing ECAP in simulated body fluid (SBF) as a saline solution close to blood plasma. In this study, multi-pass ECAP is conducted on CP-Ti at room temperature and then the axial fatigue test is performed in SBF environment with temperature 37 °C. The comparison of stress-cycle curves demonstrated that corrosion-fatigue resistance of ECAPed CP-Ti is extremely higher than initial annealed one. Moreover, it was observed that by increasing the pass number of ECAP, corrosion-fatigue resistance improves significantly. Furthermore, these results are compared to fatigue behavior of CP-Ti in air environment. The results show that corrosion-fatigue resistance of unECAPed and ECAPed CP-Ti in SBF is slightly lower than fatigue ones in air. According to the results of this experimental research, it is concluded that UFG CP-Ti has an awesome corrosion-fatigue resistance in human body and it is very suitable for utilizing as material of implants.

Effects of Zn Addition on Microstructural Evolution, Mechanical Properties, and Corrosion Resistance of Al‐6Mg Alloy Subjected to Equal Channel Angular Pressing Processing at 200 °C

The evolution of microstructure, mechanical properties, and corrosion performance of Al‐6Mg and Al‐6Mg–1Zn alloys processed using equal channel angular pressing (ECAP) at 200 °C is systematically investigated. Microstructural analysis reveals that different T and β phases are generated in the two studied alloys, resulting in different grain refinement processes. The average size of T phase in Al‐6Mg–1Zn alloy increases first and then decreases, and the distribution of T phase inside grains becomes denser with increasing ECAP deformation. The continuity of T phase at the grain boundary increases from 0 to 2 passes and decreases from 2 to 4 passes. In contrast, the β phase in Al‐6Mg alloy mainly locates at grain boundaries and becomes coarser and more continuous from 0 to 4 passes. The fracture strength of Al‐6Mg–1Zn alloy after 4‐pass ECAP reaches 391 MPa with a fracture elongation of 28%, which is superior to that of 4‐pass ECAP Al‐6Mg alloy. The 4‐pass ECAP Al‐6Mg–1Zn alloy has a higher corrosion resistance compared to the Al‐6Mg alloy under the same deformation condition. The low corrosion susceptibility in 4‐pass ECAP Al‐6Mg–1Zn alloy is attributed to sparse distribution of the T phase along the grain boundary.

Investigation of Microstructure and Mechanical Properties of SLM-Fabricated AlSi10Mg Alloy Post-Processed Using Equal Channel Angular Pressing (ECAP).

With the aim of improving the excellent mechanical properties of the SLM-produced AlSi10Mg alloy, this research focuses on post-processing using ECAP (Equal Channel Angular Pressing). In our article, two different post-processing strategies were investigated: (1) low-temperature annealing (LTA) and subsequent ECAP processing at 150 °C; (2) no heat treatment and subsequent ECAP processing at 350 °C, 400 °C and 450 °C. The microstructure and mechanical properties of this alloy were analyzed at each stage of post-treatment. Metallographic observations, combined with SEM and EBSD studies, showed that the alloys produced by SLM have a unique cellular microstructure consisting of Si networks surrounding the Al-based matrix phase. Low-temperature annealing (LTA), followed by ECAP treatment, facilitated the microstructural evolution of the alloy with partial breakup of the Si network and observed nucleation of β-Si precipitates throughout the Al matrix. This resulted in a Vickers microhardness of 153 HV and a yield strength of 415 MPa. The main results show that post-processing of SLM-produced AlSi10Mg alloys using ECAP significantly affects the microstructural evolution and mechanical properties of the alloy.

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.

A comparative study of hydrogen storage properties of AZ31 and AZ91 magnesium alloys processed by different methods

We studied the hydrogen storage properties of commercial AZ31 and AZ91 magnesium alloys with refined microstructure. Various processing techniques, such as equal channel angular pressing (ECAP) and high energy ball milling (HEBM), were utilized to modify the microstructure and phase composition of the alloys. X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical digital microscopy (ODM) were utilized to characterise the microstructure and phase transformations during the hydrogen absorption/desorption processes. The isothermal kinetics are measured by a Sieverts’-type apparatus at the temperature of 350 ℃. In the ECAP process, the AZ31 alloy had a slightly higher storage capacity and faster absorption kinetics, absorbing 6.0 wt% (6.6 wt% - maximum) of hydrogen in less than 12 min. In the HEBM process, AZ91 absorbed 6.5 wt% of hydrogen and desorbed it in 347 ± 13 s, a faster rate than AZ31. The pressure–composition isotherms of all studied alloys at a temperature of 300 °C were determined. The processed alloys exhibited no pressure hysteresis. The microstructure of bulk samples and the morphology of prepared powders were shown to affect their hydrogenation behaviour. The activation energies for hydrogen desorption were 119 ± 2 kJ/mol for AZ31 alloy processed by ECAP and 128 ± 3 kJ/mol for AZ91 alloy processed by HEBM, which are significantly lower than the activation energy values of pure Mg hydride.

Optimizing the ECAP Parameters of Biodegradable Mg-Zn-Zr Alloy Based on Experimental, Mathematical Empirical, and Response Surface Methodology.

Experimental investigations were conducted on Mg-3Zn-0.6Zr alloy under different ECAP conditions of number of passes, die angles, and processing route types, aimed at investigating the impact of the ECAP parameters on the microstructure evolution, corrosion behavior, and mechanical properties to reach optimum performance characteristics. To that end, the response surface methodology (RSM), analysis of variance, second-order regression models, genetic algorithm (GA), and a hybrid RSM-GA were utilized in the experimental study to determine the optimum ECAP processing parameters. All of the anticipated outcomes were within a very small margin of the actual experimental findings, indicating that the regression model was adequate and could be used to predict the optimization of ECAP parameters. According to the results of the experiments, route Bc is the most efficient method for refining grains. The electrochemical impedance spectroscopy results showed that the 4-passes of route Bc via the 120°-die exhibited higher corrosion resistance. Still, the potentiodynamic polarization results showed that the 4-passes of route Bc via the 90°-die demonstrated a better corrosion rate. Furthermore, the highest Vicker's microhardness, yield strength, and tensile strength were also disclosed by four passes of route Bc, whereas the best ductility at fracture was demonstrated by two passes of route C.

Strengthening of duplex stainless steel processed by equal channel angular pressing (ECAP)

This manuscript presents the study of the microstructural evolution, plastic anisotropy, and mechanical behavior of a duplex stainless steel (DSS) processed by the equal channel angular pressing (ECAP) technique. The ECAP process produced shear bands affecting both phases, austenite and ferrite, which in turns act as preferential sites for the appearance of the new ultrafine grains. Microstructural observations indicated grain sizes smaller than 300 nm in both phases. However, marked differences in the grain boundary misorientations were observed. Most ferrite grain boundaries showed low misorientations (average misorientation of 30°). In contrast, the austenite grain boundaries were mainly dominated by high-angle grain boundaries (average misorientation of 39°). The ECAP processing allowed to reach a yield strength over 1.1 GPa after one ECAP pass. Dislocations formed walls in the ferrite, while they were distributed evenly in the austenite grains creating plastic gradients between the two phases. Through the visco-plastic self-consistent model, it was found that austenite and ferrite strain hardening at different rates, generating plastic instabilities at different strain magnitudes. In this way, it was shown that austenite is the phase that provides more hardening while ferrite provides ductility. Regarding the anisotropy of the steel, crystal plasticity simulations showed that during the first passes of ECAP, the Lankford coefficients increase notably due to the heterogeneous microstructure of sheared grains with a higher density of defects forming subgrains in ferrite than austenite. Moreover, the austenite was more responsible for the larger planar anisotropy (Delta r = 2.18) values than ferrite (Delta r = 1.67) after two ECAP passes.

Recent Advances in the Equal Channel Angular Pressing of Metallic Materials

Applications of a metallic material highly depend on its mechanical properties, which greatly depend on the material’s grain sizes. Reducing grain sizes by severe plastic deformation is one of the efficient approaches to enhance the mechanical properties of a metallic material. In this paper, severe plastic deformation of equal channel angular pressing (ECAP) will be reviewed to illustrate its effects on the grain refinement of some common metallic materials such as titanium alloys, aluminum alloys, and magnesium alloys. In the ECAP process, the materials can be processed severely and repeatedly in a designed ECAP mold to accumulate a large amount of plastic strain. Ultrafine grains with diameters of submicron meters or even nanometers can be achieved through severe plastic deformation of the ECAP. In detail, this paper will give state-of-the-art details about the influences of ECAP processing parameters such as passes, temperature, and routes on the evolution of the microstructure of metallic materials. The evolution of grain sizes, grain boundaries, and phases of different metallic materials during the ECAP process are also analyzed. Besides, the plastic deformation mechanism during the ECAP process is discussed from the perspectives of dislocation slipping and twinning.

An Overview of Deformation Path Shapes on Equal Channel Angular Pressing

In recent years, research on ultra-fine grain materials has gained attention. While attempts have been made to improve the properties of the material, it has also become increasingly important to decrease the costs. Studies on improving material properties have revealed new production methods or have required the revision of existing production methods. In this direction, severe plastic deformation methods have come to the fore as a good alternative, and by improving the methods with new variations, materials with grain sizes below 1 µm have been obtained. In addition, this method positively affects the mechanical properties of the material. In this study, the Equal Channel Angular Pressing (ECAP) method, one of the severe plastic deformation methods, which has attracted great attention among researchers, was examined and the development stages of the method were investigated according to recent studies. The effective parameters in the method were examined and the effects of these parameters on the grain structure and mechanical properties of the material were discussed. Channel shapes, which are open to innovation and increase the efficiency of the ECAP method, were kept in the foreground among the prominent parameters in the ECAP process, and the results of the design changes made with new variations were examined.

Overcoming the strength-ductility trade-off in additively manufactured AlSi10Mg alloy by ECAP processing

To overcome the trade-off between strength and ductility of the additively manufactured AlSi10Mg alloy used in the automotive and aerospace industries, samples with multilevel structural heterogeneities were produced using single-pass ECAP at 150 °C and 200 °C. The microstructures of these samples were composed of partially ruptured Al/Si cellular networks and alternatively arranged zones of elongated (pancaked) grains separated by wide zones composed of ultrafine grains. Experimental results demonstrated that AlSi10Mg deformed at 150 °C, exhibited a superior ultimate tensile strength (UTS) of ~541 MPa, but limited ductility. The sample deformed at 200 °C exhibited both high ultimate tensile strength (UTS ~463 MPa) and excellent elongation at break of ~16.3%. Those results revealed a superior combination of strength and ductility that originated from bimodal grain size distribution, Orowan bowing, mechanical twinning of the hard Si phase, and back-stress hardening. Our results shed new light on the unexploited potential in improving the mechanical properties of additively manufactured alloys.

Tension-compression asymmetry of quadruple CuCoNiBe alloys processed by high-temperature multi-pass equal channel angular pressing (ECAP)

Abstract Among copper alloys, the precipitation (age) hardening quadruple CuCoNiBe alloys due to their superior mechanical properties in terms of the highest strength and elasticity achieved by peak aging have been used over the years in a wide range of industrial applications including aircrafts, coil systems, blast-proof materials, and molding dies. Combined thermomechanical treatment (i.e., equal channel angular pressing [ECAP] processing followed by post-ECAP aging) can result in a further enhancement of the strength of CuCoNiBe alloys due to the grain refinement and the formation of fine precipitates from α-Cu supersaturated solid solution. In this study, for the first time, the effect of severe plastic deformation by ECAP processing on the mechanical behavior of CuCoNiBe alloys is discussed thoroughly based on the material responses to tensile and compressive loading conditions. The results show that, besides a considerable strength enhancement, ECAP processing leads to a strong tension-compression asymmetry and significantly accelerated precipitation kinetics in CuCoNiBe alloys.

Correction to: Design and analysis of ECAP Processing for Al6061 Alloy: a microstructure and mechanical property study

Correction to: Design and analysis of ECAP Processing for Al6061 Alloy: a microstructure and mechanical property study

Insight into dislocation activity during ECAP processing of AISI 304 stainless steel studied by X-ray diffraction profile analysis

Insight into dislocation activity during ECAP processing of AISI 304 stainless steel studied by X-ray diffraction profile analysis