Single Equal Channel Angular Pressing Pass Research Articles

Effect of Zinc and Severe Plastic Deformation on Mechanical Properties of AZ61 Magnesium Alloy.

This study investigates the effects of zinc (4 wt.%) and severe plastic deformation on the mechanical properties of AZ61 magnesium alloy through the stir-casting process. Severe plastic deformation (Equal Channel Angular Pressing (ECAP)) has been performed followed by T4 heat treatment. The microstructural examinations revealed that the addition of 4 wt.% Zn enhances the uniform distribution of β-phase, contributing to a more uniformly corroded surface in corrosive environments. Additionally, dynamic recrystallization (DRX) significantly reduces the grain size of as-cast alloys after undergoing ECAP. The attained mechanical properties demonstrate that after a single ECAP pass, AZ61 + 4 wt.% Zn alloy exhibits the highest yield strength (YS), ultimate compression strength (UCS), and hardness. This research highlights the promising potential of AZ61 + 4 wt.% Zn alloy for enhanced mechanical and corrosion-resistant properties, offering valuable insights for applications in diverse engineering fields.

Refractory High‐Entropy Alloys Produced from Elemental Powders by Severe Plastic Deformation

A comparative investigation of two fundamentally different approaches for the synthesis, microstructure evolution, and mechanical properties of the refractory high‐entropy alloys (RHEA) HfNbTaTiZr and HfNbTiZr is performed. The two methods comprises conventional arc (button) melting and a powder route based on mechanical alloying and consolidation via severe plastic deformation. In particular, blended elemental powder is pre‐compacted and subjected to one or four passes of equal channel angular pressing (ECAP) at 500 °C and then 10 revolutions of high pressure torsion (HPT) at room temperature to an effective strain between 4 and 40. Some samples are then annealed at 500 °C for 1 h to investigate the thermal stability of the phases. The four ECAP passes at 500 °C do not result in the formation of the body‐centered cubic (BCC) phase typical for the program RHEAs despite the presence of interfacial zones between particles and defect‐driven diffusion. Nevertheless, a single ECAP pass is sufficient to create a solid bulk sample for subsequent HPT. After 10 HPT revolutions, in contrast to melting route resulting in a single BCC phase alloy, both alloys form new phases comprising a Nb‐rich BCC phase and a ZrHf‐rich HCP phase in both alloys.

3D FEM simulation on Deformation and Strain analysis for grain refinement of Mg Alloy passed through ECAP

Equal Channel Angular Pressing (ECAP) is a cutting-edge Severe Plastic Deformation (SPD) process for grain refining of materials up to ultra-fine or nanostructured standards, resulting in superior mechanical properties. To consider the effect of each processing parameter on the end results, computer simulation is one of the better alternatives to real ECAP deformation. The alloys used in this study are AZ61 magnesium alloy, which is a difficult material to work with in automotive applications. The ECAP process is subjected to 3D FEM simulation using ANSYS software in order to better understand the process/die design parameters. 90° channel angles and corner angles 20° i.e the best combination suggested by experimental studies were used in the simulation. For a single ECAP pass, the ECAP phase was simulated. Extrusion load, established stresses, effective strain, and temperature variation on the processed material were all noted in the results. The minimum channel angle produces the highest temperature profile on the material, developing maximum stress and strain at the deformation zone, according to the observed results. Furthermore, the results obtained using such computational techniques show that the shear strain decreases as the channel and corner angle increase.

Deformation analysis of Al Alloy AA2024 through equal channel angular pressing for aircraft structures

ABSTRACT Equal Channel Angular Pressing (ECAP) is one of the most innovative Severe Plastic Deformation (SPD) methods used for grain refinement of materials up to ultra-fined or Nano structured level which leads to superior mechanical properties. Computer simulation is one of the best alternative of actual ECAP deformation to know the influence of each processing parameters on end results. In the present work, AA2024 alloys is used, which is a demanding material in aircraft structure and automotive applications. To understand the process/die design parameter, 3D FEM simulation is done on ECAP process using DEFORM-3D software. Simulation was done on different channel angles such as 90º, 105º, 120º and 135º and corner angles such as 0º, 10º, 20º and 30º. The ECAP process was simulated for a single ECAP pass. The results concern to the extrusion load, developed stresses, effectivestrain and temperature variation on the processed material were noted obtained. From the observed results, it was found that the minimum channel angle produces the maximum temperature profile on the material, develop maximum stress and strain at deformation zone. Additionally, the outcome acquired by such computational technique illustrate that the shear strain decrease with increase in channel and corner angle.

Strain partitioning by recurrent shear localization during equal-channel angular pressing of an AA6060 aluminum alloy

We report on recurrent shear localization by formation of strictly alternating shear and matrix bands during equal-channel angular pressing (ECAP) of a 6000 series aluminum alloy. The strain partitioning process is documented by analyzing the deformation of a grid of indents as well as reconstructing the corresponding flow lines. Interestingly, shear strains of ∼3.6 in the shear bands considerably exceed the conventional maximum shear strain achievable in a single ECAP pass, whereas much lower strains occur in the matrix bands, maintaining on average the macroscopic deformation that is expected for ECA-pressing with a 90° die. Microstructural analysis by electron back-scatter diffraction (EBSD) and scanning transmission electron microscopy documents the different stages of microstructural evolution in shear and matrix bands and confirms the pronounced differences associated with the novel strain partitioning process. Furthermore, an EBSD-based analysis of texture evolution for billets with different orientations with respect to the initial extrusion direction demonstrates the important role that texture softening plays in triggering shear localization in two characteristic orientations as opposed to homogeneous deformation in the third orientation. Shear banding during ECAP is often interpreted in the light of failure mechanisms and cracking; the present study demonstrates that stable strain partitioning facilitates the fabrication of bulk laminated materials by ECAP.

Mechanical Properties of ARMCO® Iron after Large and Severe Plastic Deformation—Application Potential for Precursors to Ultrafine Grained Microstructures

Ultrafine grained (UFG) metals processed by severe plastic deformation (SPD) are well known for their outstanding mechanical properties, yet, current applications are very limited mostly due to the elaborate processing. The present work investigates the microstructures and mechanical properties of precursors to UFG microstructures that evolve at strains below the levels required for UFG microstructures, which implies less processing effort. ARMCO® iron is subjected to a single pass of equal channel angular pressing (ECAP), cold rolling, as well as a combination of both processes and compared to strain–free samples and a UFG reference condition subjected to five ECAP passes. All conditions are characterized regarding their microstructures and mechanical properties using electron backscatter diffraction, tensile tests, and rotating bending fatigue test. The precursor states show intermediate properties in between those of the strain-free and the UFG reference condition. Compared to the processing effort, the difference in properties between precursors and UFG reference is relatively small. Especially a combination of a single ECAP pass followed by cold rolling is a good compromise in terms of processing effort and mechanical properties with an endurance limit being less than 10% lower as compared to the UFG reference condition.

Strain-induced selective grain growth in AZ31 Mg alloy sheet deformed by equal channel angular pressing

In this work the microstructure development during annealing of AZ31 sheets processed by equal channel angular pressing (ECAP) is presented. Samples with dimensions of 200×200×1.8mm3 were processed in a single ECAP pass at 225°C using a channel angle of 130°. Subsequent isothermal and isochronal heat treatments were used to reveal the microstructure stability of the ECAPed sheets at temperatures between 180 and 300°C. A systematic analysis of the microstructure development was conducted using optical microscopy and electron backscatter diffraction (EBSD). It was found that a texture modification produced by the profuse activation of 101-2 extension twinning during ECAP is lost during annealing as a result of thermal detwinning. Moreover, a bimodal microstructure composed by small and coarse grains was observed at 250°C and 300°C as a result of the fast growth of a few grains. The reason for the selective grain growth is related with the activation of strain induced grain boundary migration which was stimulated by the large stored strain contained in the as-ECAP processed sheets. The dissolution of Mg17Al12 particles during annealing is also seen as a possible factor for the onset of rapid grain growth.

Improvement in cold formability of AZ31 magnesium alloy sheets processed by equal channel angular pressing

The microstructure, texture development and mechanical properties of AZ31 magnesium alloy sheets processed by equal channel angular pressing (ECAP) were investigated in this work. The results were correlated with the forming behavior at room temperature after single ECAP pass at different processing temperatures. A novel tool was developed for the implementation of ECAP to deform sheets with dimension of 200×200×1.8mm3. ECAP trials were carried out successfully at three temperatures of 175, 200 and 225°C using a channel angle of 130°. After the ECAP process, significant grain refinement and texture changes occurred in the AZ31 sheets. In particular, dynamic recrystallization was observed in the ECAPed sheets at 225°C. The tensile tests at room temperature showed that uniform elongation along the pressing direction (PD) increased with increasing processing temperature. The highest uniform strain at room temperature was 17.6% in the ECAPed sheet at 225°C. Forming tests of a U-channel section at room temperature revealed that the drawing depth of the ECAPed sheet at 225°C was improved by more than 50% as compared with the as-rolled condition.

Deformation behavior of Mg single crystals during a single ECAP pass at room temperature

Five kinds of pure magnesium single crystals with different crystal orientations were prepared and then pressed into an equal channel angular pressing (ECAP) die at room temperature. Deformation behavior and change in crystal orientations were investigated. The c-axis of the single crystals was mainly oriented to normal direction (ND) in spite of the different initial crystal orientations. Deformation and crystal rotation of the single crystals resulted from basal slips and {101¯2} twinning. ECAP deformation first led to basal slip activation and then {101¯2} to twinning. The twin propagated and occupied large areas of single crystals. In the primary large twin, basal slips were activated again, generating secondary twins. Dynamic recrystallization occurred within the secondary twins despite being at room temperature. The final orientations, whose c-axes are parallel to ND, agree with texture in ECAPed pure Mg polycrystals at a high temperature. The effect of temperature on the texture development would be small in pure Mg polycrystals.

Effect of Equal Channel Angular Pressing on Lamellar Microstructures in Nickel Aluminum Bronze

A lamellar nickel aluminum bronze has been processed by equal channel angular pressing (ECAP) and its microstructure investigated. The orientation, spacing, and morphology of the lamellae after ECAP were observed to be dependent on the orientation of the lamellae before ECAP with respect to the shear plane. Two distinct microstructures were produced following a single ECAP pass. The most common type consisted of fragmented lamellae with a reduced lamellar spacing, inclined between >0 deg and 45 deg and <180 deg, with exceptions at 0/180 deg and 45 deg. A model describing the evolution of lamellar microstructures subjected to a single ECAP pass has been proposed.

Effect of SiC‐Reinforcement and Equal‐Channel Angular Pressing on Microstructure and Mechanical Properties of AA2017

AbstractThis article deals with powder metallurgical production and modification of properties of a composite material based on an age‐hardenable Al–Cu alloy. The main objective is to improve the mechanical properties by particle reinforcement and equal‐channel angular pressing (ECAP). Our approach makes use of four hardening mechanisms: precipitation hardening, particle reinforcement, strain‐hardening, and grain boundary hardening associated with an ultrafine‐grained microstructure produced by ECAP. The main processing steps are high‐energy ball milling, hot‐isostatic pressing, extrusion, heat treatment, and a single ECAP pass. Microstructures are analyzed by optical microscopy, scanning electron microscopy, and scanning transmission electron microscopy. The mechanical properties are characterized by hardness measurements and quasi‐static tensile testing. Our experimental results show that the proposed processing route results in a nearly homogeneous distribution of SiC particles in the matrix. The combination of particle reinforcement and ECAP leads to an improvement of ultimate tensile strength by almost 300 MPa compared to the unreinforced alloy. A subsequent heat treatment leads to a further increase in hardness and strength that can be related to changes in the defect structure. Our study provides detailed information on how processing steps, microstructures, and mechanical behavior are interrelated in this technologically relevant class of materials.

Finite Element Analysis of Severe Plastic Deformation of Difficult-to-Work Material by Equal-Channel Angular Pressing at Ambient Temperature

An alternative technique of the equal-channel angular pressing (ECAP) process for difficult-to-work materials at ambient temperature is proposed by embedding a difficult-to-work material into an easy-to-work material. The easy-to-work material as a host material assists the deformation of the difficult-to-work material. The ECAP process is simulated by the finite element method (FEM). For this study, Ti as the difficult-to-work material is embedded into an Al-based functionally graded material (FGM) matrix. FEM is conducted with Ti embedded into a different host material type as well as a different die channel geometry. The strain distribution of the specimen after a single ECAP pass is analyzed. From the obtained results, it is found that the strain distribution in Ti is strongly influenced by the host material and the shape of the die channel.

Microstructural and mechanical characteristics of EUROFER’97 processed by equal channel angular pressing

EUROFER’97 was processed by equal channel angular pressing (ECAP) at 823K for a total of 4 or 8 passes, using a die angle of 105°, and its microstructure and tensile behavior in temperature range 568–873K investigated. A single ECAP pass developed a deformation texture {110} 〈011〉 that was practically stable during subsequent ECAP passes. The materials processed by 1 or 2 passes exhibited a fine microstructure of recovered subgrains and tensile behavior very similar to that for the tempered material in the as-received condition. The materials processed using 4 or 8 passes exhibited nearly equiaxial submicron grained structures with a high density of high-angle grain boundaries. These materials became softer than the as-received material at a testing temperature of ∼823K. EUROFER ECAP processed under the present conditions exhibited hardening ratio somewhat higher than that of the as-received material.

Equal Channel Angular Pressing of Canned 2124-Al Compacts: Processing, Experiments, and Modeling

A detailed experimental and computational investigation of the influence of equal channel angular pressing (ECAP) on the microstructure and properties of precompacted 2124-Al nanostructured powder, canned in copper, was conducted. Measurements and observations were obtained by densitometry and optical, scanning, and transmission electron microscopy. Based on experimental observations, it was found that hot compacts subjected to a single ECAP pass had significant microstructural refinement and subgrain formation, and significant density changes were not attained. Green compacts, on the other hand, were observed to lose coherency under ECAP. Three-dimensional finite element modeling of the ECAP process was also conducted to further elucidate the evolution of the extrusion process, and to understand how it affects plastic strains, porosity, and thermal distributions.

3D finite element analysis on strain uniformity during ECAP process

The uniformity of plastic strain distribution in a workpiece after equal channel angular pressing (ECAP) was studied using finite element software ABAQUS in 3D. Processing parameters including the channel intersection angle Φ, channel outer curvature Ψ, pressing speed, friction and processing route were varied to study their effects on strain homogeneity. It was found that a single ECAP pass was unable to produce homogenous strains in a workpiece although strain distribution can be improved by selecting the appropriate processing parameters. Multiple ECAP passes improved strain homogeneity significantly.

The principles of grain refinement in equal-channel angular pressing

Equal-channel angular pressing (ECAP) is a convenient processing tool for introducing very significant grain refinement, typically to the submicrometer level, in a wide range of metals. It is shown by experiment that processing by ECAP produces very similar microstructures in single crystals and in polycrystalline materials. Thus, after a single ECAP pass, aluminum single crystals and polycrystalline high-purity aluminum both exhibit microstructures consisting of bands of elongated subgrains and the experiments on single crystals have established unambiguously that these bands lie with their longer axes oriented parallel to the primary slip system. A model for grain refinement is developed incorporating the major experimental observations. Calculations of the shearing patterns for different processing routes lead to the conclusion that an equiaxed microstructure is achieved most rapidly in ECAP when slip occurs on three orthogonal planes over a wide range of angles: an example is route B C where the sample is rotated by 90° in the same sense about the longitudinal axis after every pass through the ECAP die.

Texture Formation during Severe Plastic Deformation

The paper represents results of computer modeling of texture formation in pure copper subjected to severe plastic deformation (SPD) realized by equal channel angular pressing (ECAP). Several polycrystalline models, namely the Taylor model, Sachs model, and self-consistent viscous plastic (VPSC) model, were applied and their predictions of texture evolution for different routes and number of ECAP passes were compared. For these calculations, simple shear deformation was used for the deformation realized by ECAP. Using the VPSC model, a single ECAP pass was revisited, but employing a 3D model of material flow, conducted by the variation-difference method, for the ECAP deformation. The influence of the inner and outer radii at the channel intersection and the friction coefficient on the homogeneity of the texture development in the cross section of the bulk ingot was investigated.