Equal Channel Angular Extrusion Research Articles

Design, Finite Element Analysis and Optimization of Helical Angular Pressing (HAP) Method as a Novel SPD Technique

Severe Plastic Deformation (SPD) processes improve the mechanical properties of materials by obtaining Ultra Fine Grained (UFG) materials, orienting the grains and reforming the grains. Helical Angular Pressing (HAP) is a newly proposed Severe Plastic Deformation (SPD) method. In order to improve the efficiency of the HAP method, its die geometry should be optimized first. In this context, four parameters (helical diameter, helical pitch, helical height and channel radius) were determined for the die channel geometry, each with four levels according to the literature. Then, thanks to Taguchi L16 combinations, 16 Finite Element Analyses (FEA) were carried out using Deform 3D software instead of 256 simulations, and effective strain values and maximum pressing load values were obtained. Later on, using the SPSS 16 software, Taguchi optimization was carried out to obtain the optimum HAP die channel geometries by minimizing the press load and maximizing the effective strain values. Next, the Finite Element Analysis (FEA) was repeated with these determined optimum die channel parameters. Finally, the efficiency of this novel HAP method was compared with conventional Equal Channel Angular Pressing (ECAP) and Twist Extrusion (TE) methods. As a result, HAP method provides effective strain values equivalent to 10 number of passes after processing with ECAP. And it is approximately 4 times higher than that achieved by TE processing. As a result of the Taguchi optimization, it is concluded that the values in the combination of diameter (d)=60 mm, height (h)=50 mm, radius (r)=4 and pitch (p)=1.25 are the optimum die geometry. In conclusion, these results indicate that the proposed novel HAP method is an efficient and applicable SPD technique.

Influence of Equal Channel Angular Extrusion and Heat Treatment on High Temperature Oxidation Resistance of Ti555 Alloy

Influence of Equal Channel Angular Extrusion and Heat Treatment on High Temperature Oxidation Resistance of Ti555 Alloy

The effect of dual thermomechanical processing paths on resulting microstructure and quasi-static mechanical properties of Mg-1Zn-0.2Ca

In this work, cast Mg-1Zn-0.2Ca (wt%) was thermomechanically processed using a two-step procedure to identify the impact of both processing steps on the resulting microstructure and mechanical properties. Samples were first preprocessed via rolling or conventional extrusion (at 400 °C), followed by Equal Channel Angular Extrusion (ECAE), utilizing routes A or Bc. ECAE was performed at 300 °C for the first pass, followed by 275 °C, 250 °C, and 225 °C for passes 2–4. Subsequent microstructures, textures, and quasi-static tension test results are presented to illuminate the effect of preprocessing and ECAE route on grain size refinement and mechanical behavior. Preprocessing via rolling yielded a smaller, more homogeneous initial grain size than the conventionally extruded material. After the second processing step, ECAE, the microstructural differences due to the preprocessing methods are reduced, but not eliminated, and mechanical properties show little variation between rolling and extrusion. The ECAE route did not impact the microstructural refinement, however, the 4Bc route did lead to enhanced ductility (>36%) and higher average ultimate tensile strengths, compared to the 4A route, when tested in the normal direction (perpendicular to the ECAE extrusion direction). The relative importance of texture alteration versus grain refinement and homogeneity is highlighted herein. Lastly, we comment on the influence of processing routes on inclusions and voids.

Indentation creep behavior of Fe–8Ni–xZr oxide dispersion strengthened alloys

Abstract This study was conducted to understand the creep behavior of two oxide dispersion strengthened alloys containing Zr as the alloying addition by performing indentation creep tests at room temperature. The oxide dispersion strengthened alloys were Fe–8Ni–xZr (x = 1 and 4 at.%, i.e., Zr-1 and Zr-4 alloys, respectively), which had been previously fabricated by mechanical alloying; followed by consolidation via equal channel angular extrusion at 1000 °C. The indentation tests were conducted under a maximum load of 100 mN with the loading rates at 300 and 400 mN min−1. The hardness was calculated by the Oliver–Pharr method, and the creep properties, such as the creep displacement, creep strain rate, creep stress, and stress exponent n, were determined. The results showed that the Zr-4 alloy was harder than the Zr-1 alloy. However, the creep resistance of the Zr-1 alloy was better than that of the Zr-4 alloy. It was further demonstrated that both the hardness and creep resistance depended on the loading rate. Moreover, a possible creep mechanism was proposed. Although the tests were performed at room temperature, they can provide insight into the effect of an oxide dispersion strengthened alloys microstructure on creep at higher temperatures.

Equal Channel Angular Extrusion of Polymers: Structural Changes and Their Effects on Properties

Equal Channel Angular Extrusion of Polymers: Structural Changes and Their Effects on Properties

Texture evolution and serrated failure of AZ31B alloy subjecting to equal channel angular extrusion

Equal channel angular extrusion (ECAE) is considered the most promising method for improving strength and ductility. The microstructures after ECAE have been extensively studied for Mg alloys relating to mechanical properties. However, the changes in texture and their relationship with the prior conditions, extrusion conditions and extrusion directions are rarely studied. In the current work, the changes in texture of AZ31B Mg alloys were investigated along the normal direction (ND), transverse direction (TD), and rolling direction (RD) after ECAE processing one pass. The results revealed a rule that the AZ31B alloy follows for texture changes, where the basal texture (namely the focused c-axis) orients 45º or nearly orients 45º, regardless of the pre-extrusion texture, extrusion temperature, and extrusion rate. Interestingly, serrated failure sorely occurs along the ND for all extrusion conditions, due to the basal slip in an unfavorable orientation and the shear plane not parallel to either pyramidal slip directions.

Minor titanium addition markedly improves the co-deformability of copper-tantalum composites

We investigated the microstructures of equal channel angular extrusion (ECAE) processed sintered composites of copper (Cu) and tantalum (Ta). These composites were produced with nominal Ta volume percentages ranging from 25% to 75%. Additional composites of the same nominal Ta content were prepared with a minor amount of titanium (Ti) added to facilitate interphase bonding. Ti addition was found to markedly improve the strength and co-deformability of the composites, allowing reliable extrusion of Cu–Ta composites with novel microstructures. A major influence of the Ti appears to be to soften the Ta, which contributes to improved co-deformability by reducing the flow stress mismatch between the composite constituents. A change in the fracture surface morphology in the Ti-modified composite compared to the unmodified composite suggests that the Ti may also improve cohesion between Cu and Ta by reducing Ta surface oxides.

Microstructure Evolution and Local Hardness of Mg–Y–Zn Alloys Processed by ECAE

Mg–9 at%Y–6 at%Zn and Mg–2 at%Y–1 at%Zn alloys were processed by equal-channel-angular extrusion (ECAE) to investigate their microstructure evolution and local hardness. The area fraction of the kink bands in the Mg–9 at%Y–6 at%Zn alloys increased with increasing the number of ECAE passes, resulting in higher hardness. In contrast, the number of kink boundaries in the local region near the indentation was almost constant. The relationship between the microstructure factors of the kink bands and the local hardness is discussed in comparison with the forged alloy. In the Mg–2 at%Y–1 at%Zn alloys, the microstructural evolution of the α-Mg matrix phase and long-period stacking ordered (LPSO) phase by 1-pass ECAE and the increase in local hardness were discussed.

Wear behavior of in-situ oxide dispersion strengthened Fe-8Ni alloy with Zr additions

In this study, in-situ oxide dispersion strengthened (ODS) Fe91Ni8Zr1 and Fe88Ni8Zr4 alloys were produced by combination of high energy mechanical alloying (HEMA) and high temperature equal channel angular extrusion (HT-ECAE). The wear behaviors of the consolidated samples were investigated under different loads from 1 N to 4 N by reciprocating wear tests at room temperature. The Scanning electron microscopy (SEM) was used to examine the wear tracks to analyze the wear characteristics as a function of applied loads. The relative comparison of the wear results showed that under the lower loads of 1 N and 2 N, Fe88Ni8Zr4 alloy has lower wear rate than Fe91Ni8Zr1 alloy whereas under the higher loads of 3 N and 4 N, it is vice versa. Additionally, the friction coefficient of Fe91Ni8Zr1 alloy was found to be lower than that of Fe88Ni8Zr4 alloy under all the applied loads. The results were comparatively discussed with respect to microstructural features of 1 at% Zr and 4 at% Zr containing ODS alloys produced by HEMA followed by ECAE. The obtained results of ODS alloys with different grain size, precipitate size, and number density of the precipitates, may disclose a new sight for using such alloys in wear applications just as cutting tools, turbine blades, and discs.

Severe plastic deformation: A state of art

The proposed application of the study on severe plastic deformation (SPD), also known as Nano-SPD, is to provide a comprehensive overview of the recent advancements and developments in the field. The focus of the study is to highlight the various continuous processes used for producing ultrafine-grained and nanostructured materials, such as equal-channel angular pressing, high-pressure torsion, twist extrusion, accumulative roll-bonding, and multi-directional forging. The study also aims to demonstrate the versatility of SPD in processing a wide range of materials, including semiconductors, alloys, glasses, polymers, ceramics, and composite materials. Furthermore, the study highlights the potential of SPD in stabilizing metastable states and synthesizing novel materials with superior functional and mechanical characteristics. The proposed application of the study is to provide a comprehensive and up-to-date review of the advancements and developments in the field of Nano-SPD and to highlight its potential in producing advanced materials with enhanced properties. This study is expected to be useful for researchers, engineers, and material scientists working in the field of materials science and engineering.

Mechanical property improvement of a AA6082 alloy by the TV-CAP process as a novel SPD method

AbstractTwisted variable channel angular pressing (TV-CAP) is a novel method. While it combines the advantages of equal channel angular pressing (ECAP), twist extrusion and direct extrusions, also it eliminates the disadvantages of these methods. Finite element analysis was also carried out in order to examine the design parameters, material flow and examine the effective strain values. Hardness and tensile tests were performed to examine the effect of TV-CAP on the mechanical properties of AA6082. In addition, optic microscope, SEM and TEM images were taken respectively and XRD, EDS and EBSD analyses were accomplished in order to investigate the microstructural analysis. As a result of this study, it has been observed that the material has hardened approximately 3 times compared to the annealed material and became 1.5 times stronger in terms of ultimate tensile strength. It was also concluded that, this new method is more efficient than twist extrusion and multi-pass equal channel angular pressing processes.

Temperature and Die Angular Effect on Tensile Strength, Hardness, Extrusion Load and Flow Stress in Aluminum 6063 Processed by Equal Channel Angular Extrusion Method

Temperature and Die Angular Effect on Tensile Strength, Hardness, Extrusion Load and Flow Stress in Aluminum 6063 Processed by Equal Channel Angular Extrusion Method

Mechanical and corrosion properties of Mg–MgO and Mg–Al2O3 composites fabricated by equal channel angular extrusion method

Equal channel angular extrusion (ECAE) has shown great potential for the consolidation of powdered materials. In the present article, the mechanical and corrosion properties of Mg–MgO and Mg–Al 2 O 3 composites produced by the ECAE method were studied. Pure magnesium reinforced with 0, 10, 20, and 30 ​vol percentages of MgO and Al 2 O 3 particles were hot consolidated at 600 ​MPa in an ECAE die without prior cold compaction or canning of the powders. Results indicated that the reinforcement content is directly proportional to the hardness, compressive strength, and corrosion resistance of the fabricated composites, while it has an inverse relationship with the relative density. The lowest relative density and the highest corrosion rate were obtained for the Mg+30%MgO composite samples, as opposed to the pure magnesium with the highest relative density and the lowest corrosion rate. Besides, composites reinforced with 30 and 20 ​vol percentages of alumina revealed the highest hardness and the highest compressive strength, which were 55% and 74% higher than that of the pure magnesium sample, respectively. Based on SEM and EDX analyses, it was shown that Mg–Al 2 O 3 samples had finer grain sizes compared to Mg–MgO composites. • ECAE was successfully implemented to fabricate Mg–MgO and Mg–Al 2 O 3 composites. • Hardness and strength are linearly related to the content of the reinforcements. • Mg–Al 2 O 3 showed remarkably higher strength and hardness compared to the Mg–MgO. • The corrosion rate of the Mg–Al 2 O 3 was lower than that of Mg–MgO.

Equal channel angular extrusion (ECAE): Die design, affecting variables and development of mechanical behavior and properties of bio-metals

There are numerous practices for producing nanocrystalline (NC) and ultrafine-grained (UFG) metals, composites, polymers and alloys; amongst which Equal Channel Angular Extrusion (ECAE) is one of the renowned techniques in metal forming processes under the severe plastic deformation process (SPD) in which a massive plastic strain is enforced on a bulk material. The novelty of this work is the design and fabrication of a split type of die specifically for carrying out ECAE on difficult-to-deform bio-metals. The die is designed for a channel angle of 120°. The study provides a detailed discussion of the pre and post-extrusion tests, process flowchart, and operational variables. This work offers a valuable opportunity to investigate the implications of the ECAE process for other challenging-to-deform metals. Additionally, the ultrafine-grained materials produced through ECAE have potential applications in industries such as automobile, power, and aerospace.

Properties and hardening behavior of equal channel angular extrusion processed Mg-Al binary alloys

We examined the competition between precipitation and grain-size refinement during equal channel angular extrusion (ECAE) of two fully solutionized coarse-grained Mg-Al alloys which was accomplished by using a “step-down” temperature method, up to 4 passes using the BC route. The extrudates show various levels of microstructural heterogeneity, especially at lower processing temperatures. Grain size refinement from hundreds of micrometers to a few micrometers was achieved by dynamic recrystallization (DRX). This is in conjunction with the formation of precipitates with a bimodal size distribution. One type is a few micrometers and found at grain boundaries, while the other precipitate type is a few hundred nanometers and found inside large parent grain remnants (PGR). The non-uniformity of the microstructure indicates that the ECAE deformation process is highly inhomogeneous. However, the presence of both fine grains and PGRs renders the extrudate with a higher capacity for actual strain hardening rate (ASHR: dσ/dε) comparable to that of the as-received materials. Dynamic compressive test results show a significant strength increase attributed to the precipitates, which is in addition to the strength improvement from grain size refinement (Hall-Petch Effect). These features validate the utility of ECAE for high-strength Mg alloy engineering. The work herein also provides microstructural insights to the severe plastic deformation (SPD) processing of Mg-Al alloys as well as a wealth of experimental data for the development of numerical models.

Microstructural evolution of Al-Mg-Er-Zr alloy by equal channel angular extrusion at room temperature

To obtain excellent mechanical properties, Al-Mg alloy was processed through a combination of equal channel angular pressing (ECAP) and micro-alloying techniques. In this study, the microstructural evolution of Al-Mg-Er-Zr alloy during ECAP at room temperature were systematically investigated. TEM results confirm that the Al3(Er, Zr) particle exists in the initial material and saturated dislocations form dense dislocation walls. The grains were refined with an average grain size of 2.8 μm after 4 passes of ECAP. Continuous dynamic recrystallization was identified and this mechanism led to the formation of fine grain structure. The (101)-oriented coarse grains were relatively stable once they had been formed.

Influence of Equal Channel Angular Extrusion on the Behavior of Lead Alloy

Equal Channel Angular Pressing (ECAP) is the most promising material processing technique involving severe plastic deformation, and has been extensively employed and analysed. The aim of this work is to examine the influence of ECAP on the behaviour of Lead alloy. The technique was applied to Lead alloy at room temperature using route C, at channel angles of 450, 600, 750, 900 and 1050. The materials were processed up to five ECAP passes. Hardness test, impact test, and microstructural changes of the processed materials were examined. Results show that extrusion force reduces as the strain level increases and that dynamic recrystallization and structural changes reduce the material hardness for all angles of ECAP. All the angles absorbed their least amount of energy at their 5th pass. Analysis of microstructure images also revealed that increasing the strain level leads to break down and dissolution of Antimony rich precipitate.

Microstructure and Mechanical Properties of Severely Deformed Polypropylene in ECAE (Equal Channel Angular Extrusion) via Routes A and C

Equal channel angular extrusion (ECAE) is a solid-state extrusion process for modifying microstructures via severe plastic deformation without modifying the specimen cross section. In this study, changes in the microstructure and mechanical properties of polypropylene resulting from extrusion orientation route A (no rotation between extrusions) and extrusion orientation route C (a rotation of 180° between extrusions) are investigated using a 90° die-angle tooling outfitted with back pressure. Important differences are reported for the ECAE-induced deformation behavior between the two processing routes. A focus is made on the occurrence of heterogeneous plastic deformations (periodic shear banding and warping) for both routes and the control and inhibition of the plastic instabilities via regulated back pressure and ram velocity. Wide-angle X-ray scattering is carried out to characterize the structural evolution as a function of the processing conditions including route, extrusion velocity and BP application. The mechanical properties of the specimens machined from the ECAE pieces are examined under different loading paths including uniaxial tension/compression and simple shear. Full-field displacements converted to volumetric strains revealed the profound impacts of the processing route on the deformation mechanisms during tensile deformation.

Lamellae orientation and structure evolution of reinforced poly(lactic acid) via equal channel angular extrusion

AbstractThe aim of this study was to improve the mechanical performance of biodegradable poly(L‐lactic acid) through equal channel angular extrusion (ECAE). Changes in morphology induced by the ECAE shear deformation in poly(lactic acid) (PLA) were investigated. Differential scanning calorimeter results suggested a significant improvement in crystallinity of ECAE‐deformed PLA depending on its thermal condition and deformation force. Two‐dimensional wide angle X‐ray diffraction measurement and polarized FTIR spectroscopies of ECAE‐deformed PLA revealed a structural network in the crystalline region, and the taut tie molecules (TTMs) connecting lamellae also stretched. Scanning electron microscope results showed that the macro‐fibrils were generated, and the oriented structures were arranged along the nominal shear direction at a certain angle. Both the inclined macro‐fibrils structure and the oriented TTMs within fibrils were beneficial in improving mechanical performance. Finally, the mechanical property tests showed that the mechanical properties of PLA were improved overall. The tensile strength, elongation, impact strength, and bending strength increased by 28%, 123.8%, 224.3%, and 47.6%, respectively. Meantime, a transition from brittle fracture to ductile fracture was observed from the original PLA billet to ECAE‐deformed one. Therefore, the ECAE process represents a promising approach for comprehensively reinforced PLA.

A new method of processing magnesium alloy thin-walled tube by direct extrusion and corrugated equal channel angular extrusion

A new method of processing magnesium alloy thin-walled tube by direct extrusion and corrugated equal channel angular extrusion