Channel Angular Extrusion Process Research Articles

Effects of Equal Channel Angular Extrusion (ECAE) Process on the Mechanical Property and Erosion Resistance of Ti–5Al–5Mo–5V–3Cr Alloy

High-strength near-β-phase titanium alloys, including Ti–5Al–5Mo–5V–3Cr, are considered the material of choice for large components that demand weight reduction and high strength. The erosion resistance of Ti–5Al–5Mo–5V–3Cr alloy is essential for many components exposed to solid particles and marine environment, but is rarely investigated. In this study, we investigate the erosion resistance and mechanical properties of Ti–5Al–5Mo–5V–3Cr alloy against silica slurry, which is formed by an equal channel angular extrusion (ECAE) process in β-phase temperature range, followed by quenching and annealing treatments. It was found that ECAE and subsequent heat treatments promote the precipitation of extremely fine α-phase particles inside β-phase grains, which lead to increased tensile strength and elongation due to the function of the α-precipitates as obstacles for dislocation sliding and the refined β-grains that avoid the stress propagation. Both the fracture toughness and impact toughness are improved as measured by the tensile test and impact test. The erosion mechanisms were analysed by the morphological analyses of the eroded surfaces, while the material microstructures were observed by a scanning electron microscope, which proved the existence of fine α-precipitates in the β-phase. Erosion resistance test was conducted, and mass loss was measured in comparison with non-ECAE-treated sample.

Equal Channel Angular Extrusion of AA 6063 Using Conventional Direct Extrusion Press

In the present work, an extrusion-equal channel angular extrusion (Ex-ECAE) process composed of two processes, extrusion and ECAE, is developed. The Ex-ECAE die contains three segments and is used directly in the conventional direct extrusion press to refine the microstructure, specifically the coarse grain layer (CGL) on the surface of the extrudate. The first segment in the die is designed to perform the normal extrusion process and the second and third segments to perform the process of ECAE. The study reveals that the CGL can be eliminated (refined) completely at the macroscale. At the microscale, the original grain is subdivided into subgrain, which contains many smaller cells. The results can be explained by the grain subdivision mechanism. The textures of the Ex-ECAE sample at various segments are measured using EBSD (Electron Backscatter Diffraction). The results reveal that the first segment of the Ex-ECAE sample has a perfect fiber texture which consists of a mixture of strong 〈001〉 and weak 〈111〉 fiber components. The texture of the second segment is a mixture of strong (1 1 0) [1 −2 1] and weak (0 1 1) [2 −1 0] fiber components. However, the main component of the second segment is a typical texture of the “alloy” or “brass” type. Finally, the texture of the extrudate (the third segment) is reversed to an incomplete fiber texture which consists of strong (0 0 1) [−1 −1 0] and weak (1 1 1) [1 −1 0].

Effect of $$\left\{ {10\bar 12} \right\}$$ extension twins on microstructure enhancement of Mg-3Al-1Zn alloy in half channel angular extrusion

This paper mainly concerns the enhancement of the microstructure and mechanical properties of the Mg-3Al-1Zn rolled sheet alloy in the half channel angular extrusion (HCAE) process, linking with effects of the starting texture and \(\left\{ {10\bar 12} \right\}\) extension twin. The initial HCAE specimens are prepared by imposing the caxis compression of 5% along the rolling direction to the Mg-3Al-1Zn sheet. They were applied in the HCAE process at the forming temperature of 523 K to make the enhanced microstructure named after HCAE-It, IIt, IIIt according to different starting textures. Improved mechanical properties and homogeneous grain structure with enhanced elongation can be achieved by the specific starting texture (HCAE-It) rather than the effect of the induced \(\left\{ {10\bar 12} \right\}\) extension twins in the initial specimen.

Effect of 2θ-Punch Shape on Material Waste during ECAE through a 2θ-Die

This article mainly focusses on the improvement of metal forming die tooling for equal channel angular extrusion (ECAE) processes through nonrectangular 2θ-dies of classical Segal geometry. The technological appropriateness of workpiece deformation through 2θ-dies using inclined oblique 2θ-punches has been evaluated with the introduction of physical simulation techniques. It has been shown experimentally that for the best efficiency, the geometric condition required for the taper angle of the inclined oblique punch is equal to the 2θ angle between the inlet and outlet channels of the angular die. Physical simulation shows that the application of an oblique inclined 2θ-punch provides workpiece dead zone area downsizing and macroscopic rotation reduction during ECAE. The use of numerical finite element modeling simulation also confirms the usefulness of the oblique inclined 2θ-punch for increase of the utilization ratio and decrease of the maximum deformation and unevenness of deformation distribution.

The Tribological Properties of Mg Alloy Produced by ECAE and Laser Melting

A new processing procedure was applied to an Mg alloy. This procedure involves the equal channel angular extrusion (ECAE) process and laser melting surface treatment. A commercial Mg alloy was first produced by equal channel angular extrusion (ECAE) process. Then the laser melting surfave treatment was carried out after ECAE. The effects of ECAE and laser melting on tribological properties of the alloy were investigated. Experimental results showed that the mechanical properties and tribological properties of the alloy were improved after ECAE. The laser melting surface treatment can further improve the tribological properties of Mg alloy.

Wear Behavior of Mg Alloy Procduced by Equal Channel Angular Extrusion

A commercial Mg alloy was prepared through equal channel angular extrusion (ECAE) process. The effect of ECAE on mechanical and tribological properties of the alloy was investigated. Experimental results showed that the hardness and strength of the alloy with ECAE were higher than that of the alloy without ECAE and increased with the increase pass number. The friction coefficient and wear resistance of the alloy after ECAE were significantly improved.

Development of Nanostructured Armco-Fe by Equal Channel Angular Extrusion (ECAE)

The Equal Channel Angular Extrusion or Pressing (ECAE/ECAP) process has been developed over these last years in order to obtain nanostructured materials by means of severe plastic deformation. These applications have been mainly focused on light alloys while its application to iron and steel has not been so common. This is due to the difficulties that their ECAE processing implies, as much higher values for the processing force are required. In this present study, the results achieved when Armco-Fe is processed by ECAE at room temperature are shown. In addition, a comparative study on the variation in the mechanical properties (yield stress, ultimate tensile strength, and elongation at break) is shown when different thermal treatments are employed. Specific combinations are also shown of the thermal treatments which lead to a higher value of elongation and mechanical strength in relation to the starting material. Furthermore, an analysis of the obtained results is made by optical and scanning electron microscopy techniques.

Comparative Analysis of Actual Processing Conditions in ECAE between FEM and Both Analytical and Experimental Results

Equal Channel Angular Extrusion (ECAE) process is a severe plastic deformation (SPD) process whose principal purpose is to impart high values of deformation to the processed material, which leads to a grain size reduction and hence to an improvement in its mechanical properties. Although the strain achieved is important in the process, the required force and the extrusion pressure are equally important design factors. Like other metal-forming processes, a compromise solution between the strain achieved and the force required has to be applied. In this study, both the finite element method (FEM) and analytical methods based on the upper bound method (UBM) were used for modelling and comparing the forces required in the ECAE process when strain-hardening materials are considered. In addition, experimental results were carried out in order to validate the FEM modelling. Several FEM simulations, with different geometric parameters, were run, and by using design of experiments (DOE) tools, a mathematical model was obtained. By using this model, the processing extrusion pressure can be predicted. In order to compare the actual behaviour of processed materials with FEM and analytical results, a 5083-AA was chosen as processed material. Nevertheless, the methodology developed could be applied to different materials with strain hardening.

Microstructure and Wear Properties of GCr15 Alloy Produced by Equal Channel Angular Extrusion

GCr15 alloy produced by hot-forged is subjected to equal channel angular extrusion (ECAE) process at 950°C. The microstructure of GCr15 steel via ECAE and annealed is studied by an optical microscope. The effect of ECAE and annealing on the wear properties of the alloy is also investigated. The results show that the grain size reduced from 50 mm to 10 mm via one pass ECAE, and the hardness of the alloy is increased. The wear mass loss of the alloy is greatly reduced due to the grain-refinement after ECAE and annealing.

A finite element simulation of NiTi alloy during equal channel angular extrusion

Particle tracking method is given to analyze the equal channel angular extrusion (ECAE) process of NiTi alloy in non-isothermal condition. The distribution of effective strain, effective stress, the temperature, and strain rate of selected particle tracking points is analyzed respectively. The influence of friction factor is also discussed. The experimental results show that under non-isothermal condition, distribution of strain, stress, strain rate and temperature are inconsistent on relative plane. Final result indicates that distribution of effective strain on xz plane is obviously different from those of isothermal condition; load predication reveals friction factor in this mechanism made little influence on the gross of load.

Comparison of deformation and microstructural evolution between equal channel angular pressing and forward extrusion using the dislocation cell mechanism-based finite element method

In order to compare plastic deformation and microstructural evolution behavior deformation between equal channel angular pressing (ECAP) and forward extrusion (FE) processes, finite element analyses in associated with the mechanism of dislocation glide and cell formation have been employed. It was found from the simulation results that the ECAP process is superior to the FE process, in terms of strength, grain refinement and deformation homogeneity as well as repeatability due to the equal channels of entry and exit.

Reheating and thixoforging of ZK60+RE alloy deformed by ECAE

The two-pass equal channel angular extrusion (ECAE) process was introduced into strain-induced melt activation (SIMA) to predeform a ZK60 alloy with rare earth (RE) addition. Microstructure evolution of ECAE-formed ZK60+RE alloy during reheating was investigated. Furthermore, tensile properties of thixoforged components were determined. The results show that the SIMA process can produce ideal microstructures, and spheroidized solid particles with little entrapped liquid can be obtained. With prolonging holding time, the size of solid particles increases and the degree of spheroidization is improved. The tensile properties of the thixoforged ZK60+RE samples are close to those of two-pass ECAE-formed samples.

Investigation on the Increasing Material Hardness on Fineblanked Sprocket

In cold working metal forming process, severe plastic deformation results in changes in the material properties. Earlier researches mainly investigated the rolling and equal channel angular extrusion (ECAE) processes. This study focuses on the fine-blanking process, specially the increasing material hardness on the fineblanked sprocket part. The microstructure around the cut surface is observed and the finite element analysis is done to clarify the mechanism of the increasing hardness as well. The microstructure revealed increasingly compressed and elongated grain structure of the contributed grain flow and orientation, as the blankholder and counterpunch forces increased. This resulted in the increased material hardness around the cut surface. Thus, these results theoretically clarified the mechanism of the increasing material hardness in the fine-blanking process regarding microstructural evolution, with the associated finite element analysis. Therefore, the special characteristic features in the fine-blanking process, result in the pronounced hardening around the fineblanked surface.

Modelling compression tests on aluminium produced by equal channel angular extrusion

The main objective of this paper was to characterize the mechanical properties of commercial purity aluminium AA1050 after being submitted to the equal channel angular extrusion (ECAE) process. Compression tests on cylindrical samples extracted from ECAE material are extensively described. The influence of ECAE conditions (number of passes, route, etc.) on the mechanical response is assessed. The extraction of the material behaviour from the experimental results is not straightforward because of inhomogeneities occurring during the test. Therefore, an inverse modelling with the finite element method was used to obtain accurate material parameters by optimization. It appeared that an accurate material yield locus (based on texture analysis) is necessary in order to reproduce the anisotropic behaviour of the ECAE material. On the other hand, its hardening behaviour during compression tests was satisfactorily represented by an elastic (near) perfectly plastic model.

A Finite Element Investigation into the Changing Channel Angular Extrusion of Brass Alloy

This study investigates a novel changing channel angular (CCA) extrusion process, in which high strains are induced within the billet by passing it through a series of channels of unequal cross-sections arranged such that they form specified internal angles. Using commercial DEFORMTM 2D rigid-plastic finite element code, the plastic deformation behavior of CuZn37 brass alloy is examined during one-turn and two-turn CCA extrusion processing in dies with internal angles of φ =90o, 120o, 135o or 150o, respectively. The simulations focus specifically on the effects of the processing conditions on the effective strain, the rotation angle and the effective stress induced within the extruded billet. The numerical results provide valuable insights into the shear plastic deformation behavior of CuZn37 brass alloy during the CCA extrusion process.

Semisolid Microstructural Evolution of Equal Channel Angular Extruded Mg-Al Alloy During Partial Remelting

Using equal channel angular extrusion (ECAE) process, which combine the advantages of grain refinement and induced strain, for preparing semisolid billets is a relatively new Strain Induced Melt Activation(SIMA)method. This paper investigates the remelting and semisolid isothermal holding behavior of Mg-9Al alloy after ECAE processing at 350°C. It has been found that 2 passes ECAE-ed billets are qualified for obtaining spherical grains after remelting and isothermal holding treatment. Increasing the ECAE process from 2 passes to 8 passes has no further significant effects on the size and roundness of the solid particles at the semisolid state. The effects of temperature and isothermal holding time on microstructural evolution have also been investigated. In addition, the solid solution treatment before the ECAE processing affected greatly on microstructural evolution of the alloy during ECAE processing and thus the following remelting and isothermal holding behavior. The Mg17Al12 precipitates were uniformly decomposed from the saturated solid solution in the solutionized samples during ECAE processing. The coalescence of grains together with the self-blocking effect generated more entrapped liquid in the solutionized sample at semisolid state. Moreover, the solid particles of solutionized samples have bigger size and grow faster, which are detrimental to SSM processability.

Effects of equal channel angular extrusion and subsequent heat treatment on tribological properties of TiNi alloy

The friction and wear properties of TiNi alloy processed by equal channel angular extrusion (ECAE) and subsequent heat treatment processing under dry sliding condition were evaluated on a block on ring M-2000 tribometer. The effects of ECAE and heat treatment on the tribological properties of TiNi alloy were investigated. The worn surface morphologies of TiNi alloy were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. The results showed that ECAE and heat treatment contributed to improve the friction and wear behaviours of TiNi alloy remarkably. The friction coefficient and wear loss of TiNi alloy decreased after ECAE and heat treatment. The maximum wear reduction was obtained when the heat treatment temperature after ECAE was 773 K. Adhesion wear and delamination were notable for the initial TiNi alloy. The material delamination was greatly abated when the heat treatment temperature of TiNi alloy processed by ECAE was 773 K.

Equal Channel Angular Extrusion (ECAE) of Ni-Ti Based Shape Memory Alloy Systems

In this paper we report the effects of Equal Channel Angular Extrusion (ECAE) processing on the phase transformation characteristics of Ni-Ti based shape memory alloys in terms of transformation temperatures, temperature hysteresis, and microstructural evolution. The ECAE process affects the material’s shape memory behavior via microstructural refinement. Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM) were utilized to investigate the effects of microtructural refinement and substructure formation on the shape memory behavior of these alloys. The microstructural refinement was found to have significant influence on the transformation temperatures.

Load predictions for non-isothermal ECAE by finite element analyses

This study is to investigate material flow and load predictions due to different interface conditions between dies and the workpiece for non-isothermal Equal Channel Angular Extrusion (ECAE) process of pure titanium CP-Ti Gr-1 alloy. The change of friction conditions was carefully investigated in terms of variation of load requirements at the beginning stage of deformation and remeshing. In order to validate the numerical results obtained, finite element simulation results were compared with the experimental data. The current investigation clearly showed the importance of proper handling of friction conditions to improve the solution accuracy especially for the ECAE process simulations. The approach will be beneficial in understanding the deformation mechanics and determining the load requirements for the ECAE with the larger specimen for industrial applications to obtain ultra-fine-grained bulk materials. [Received 30 March 2006, Accepted from 22 January 2007]

Realization of high strength and high ductility for AZ61 magnesium alloy by severe warm working

Extruded Mg–6%Al–1%Zn (AZ61) alloy bar was subjected to 4-pass Equal Channel Angular Extrusion (ECAE) processing at 448–573 K. At the processing temperature of 448 K, extremely fine grains with the average grain size of 0.5 mm are formed as a result of dynamic recrystallization originated by fine Mg17Al12 (b) phase particles having 50–100 nm diameter dynamically-precipitated during ECAE processing. The sizes of both α matrix and β phase decrease with decreasing processing temperatures. In tensile test at room temperature under the strain rate of 1×10—3 s—1, tensile strength increases with decreasing ECAE processing temperatures due to fine grains, fine precipitates and residual strain hardening. Especially, highest strength of 351 MPa was achieved in the specimen ECAE-processed at 448 K. In addition to such high strength, elongation reaches 33% in that specimen. This specimen exhibits clear strain rate dependencies of both flow stress and elongation even at room temperature. As a result, higher elongation of 67% is obtained under low strain rate of 1×10—5 s—1.In such specimen, non-basal slip and grain boundary sliding occur in addition to basal slip. Furthermore, there are grains with no dislocations, suggesting the occurrence of dynamic recovery. The contribution of all the deformation mechanisms would cause high ductility in fine-grained AZ61 alloy specimen with high strength.