Cyclic Extrusion Compression Research Articles

Influence of Equal Channel Angular Pressing and Cyclic Extrusion Compression on the Microstructure Evolution and Mechanical Properties of Pure Aluminum.

The influence of equal channel angular pressing (ECAP) and cyclic extrusion compression (CEC) of Al-1080 on the pressing load, microstructure, and tensile properties was investigated. The pressing peak loads of the CEC were 218.8-265.4% higher than those of the ECAP, with a more complex load behavior in the CEC process. The deformation morphology of the ECAP samples indicates an improvement in the deformation homogeneity with the number of passes. Shear band morphology with a decrease in the shear band width from the center to the outer surface makes up the predominant pattern of the CEC samples. The ECAP samples have 13.9-44% smaller average grain sizes, with 3.8-8.1% higher high-angle grain boundaries (HAGBs) than the CECed samples. The ECAP and CEC processing improve the tensile strength. However, the ECAP sample's tensile strength (UTS) and the proof strength (σ0.2) were 11.5-20.6 and 2.6-16.4% higher than that of CEC, without noticeable differences in elongation. The σ0.2 values were predicted accurately with a deviation range of 1.8-7.3% from the experimental one. The ECAP samples are easy to process under lower loads. Moreover, ECAP samples have an equiaxed grain microstructure with a higher degree of deformation homogeneity and tensile strength.

Processing of different Mg-based multiphase alloys via a combined severe plastic deformation

In this study, cyclic extrusion compression angular pressing-forward extrusion was employed to develop binary magnesium-based multiphase alloys, and subsequently analysed the microstructural, mechanical and corrosional properties of the resulting samples. The findings demonstrate that the inclusion of alloying elements in the multiphase alloys significantly enhances their microstructural, mechanical and corrosional properties. Compared to pure Mg samples fabricated using the same method, the multiphase alloys produced by this technique exhibit finer grain structures. Mechanical analysis indicates that these multiphase alloys possess higher yield and ultimate strength compared to pure magnesium. Corrosion testing reveals that all produced alloys outperform pure magnesium in various aspects. Particularly, Mg–1Zn and Mg–1Mn alloys exhibit exceptional corrosion resistance in immersion, mass loss and polarisation tests.

Improving the tension-compression asymmetry of ZK61 magnesium alloy through texture optimization in combined extrusion

In order to improve the tension-compression asymmetry that exists widely in extruded magnesium alloys, ZK61 magnesium alloys with different texture characteristics were prepared by conventional extrusion, compression-extrusion, and cyclic extrusion compression. The effect of texture on the tension-compression asymmetry and associated deformation mechanisms of magnesium alloys was revealed based on the Sachs assumption. Subsequently, a texture-modified Hall-Petch relationship was used to quantify the combined effect of texture and grain on both tensile and compressive yield strengths. It is found that the slight weakening of the {0002}∥LD fiber texture was beneficial to the suppression of {10‐12} twinning and the activation of prismatic slip, which in turn significantly improved the tension-compression asymmetry without the obvious sacrifice of strength. However, excessive texture inclining can cause a striking decrease in strengths and even reverse tension-compression asymmetry due to the activation of basal slip and pyramidal slip. In conclusion, slight basal texture weakening was a texture optimization strategy to obtain tension-compression symmetry and high strength for wrought magnesium alloys.

Cyclic contraction-expansion extrusion (CCEE): An innovate severe plastic deformation method for tailoring the microstructure and mechanical properties of magnesium AZ91 alloy

In this study, the Cyclic Contraction-Expansion Extrusion (CCEE) process, a novel severe plastic deformation (SPD) technique, is applied to the AZ91 magnesium alloy to enhance its mechanical properties through microstructural refinement. The CCEE method combines cyclic expansion extrusion (CEE) and cyclic extrusion compression (CEC), integrating their advantages while overcoming drawbacks. The CCEE process is capable of inducing substantial plastic strain (3.38) within a single processing cycle, eliminating the need for secondary punches or a synchronized backpressure system. The process is conducted at a temperature of 300 °C, resulting in a bimodal microstructure through the dynamic recrystallization (DRX) mechanism. This microstructure consists of refined equiaxed α-Mg grains with an average size of 2.8 μm, surrounded by a network of newly nucleated α-Mg grains and Mg17Al12 particles with an average size of 500 nm in the two-pass processed sample. Results obtained from the tensile test technique indicate a significant enhancement in the ultimate tensile strength (UTS) of the AZ91 alloy, increasing from 139 MPa to 276 MPa and 290 MPa, and a notable improvement in elongation, increasing from 4% to 8% and 12% after two passes of the CCEE process. Macro-texture X-Ray diffraction (XRD) measurements reveal the formation of a pyramidal deformation texture in the one-pass sample, contributing to the UTS improvement. This texture weakens during the second pass, leading to an increase in elongation. Furthermore, microhardness measurements show an increase from HV 62 to HV 85 after the first pass of the CCEE and HV 73 after the second pass.

Shortening the manufacturing process of degradable magnesium alloy minitube for vascular stents by introducing cyclic extrusion compression

Due to its excellent biocompatibility and biodegradability, Mg and its alloys are considered to be promising materials for manufacturing of vascular sent. However, the manufacture of high-precision and high-performance Mg alloys minitubes is still a worldwide problem with a long manufacturing processing caused by the poor workability of Mg alloys. To solve this problem, the cyclic extrusion compression (CEC) was used to pretreat the billet by improving the workability of Mg alloys, finally shortening the manufacturing process. After CEC treatment, the size of grains and second phase particles of Mg alloys were dramatically refined to 3.2 µm and 0.3 µm, respectively. Only after three passes of cold drawing, the wall thickness of minitube was reduced from 0.200 mm to 0.135 mm and a length was more than 1000 mm. The error of wall thickness was measured to be less than 0.01 mm, implying a high dimensional accuracy. The yield strength (YS), ultimate tensile strength (UTS) and elongation of finished minitube were 220±10 MPa, 290±10 MPa and 22.0 ± 0.5%, respectively. In addition, annealing can improve mechanical property and corrosion resistance of minitubes by improving the homogeneity of the microstructure and enhancing the density of basal texture.

Microstructural and Mechanical Evaluation of Pure Copper Rods Processed by Severe Plastic Deformation Method of Hydrostatic Cyclic Extrusion Compression

Microstructural and Mechanical Evaluation of Pure Copper Rods Processed by Severe Plastic Deformation Method of Hydrostatic Cyclic Extrusion Compression

Cyclic Extrusion Compression Process for Achieving Ultrafine-Grained 5052 Aluminum Alloy with Eminent Strength and Wear Resistance

Previous studies have yet to show a consistent effect of severe plastic deformation (SPD) processing on the wear behavior of different metals and alloys. To fill this scientific gap, this study investigated the effect of the cyclic extrusion compression (CEC) process, as one of the prominent SPD techniques, on the wear behavior of AA5052. In addition, the microstructure evolution and mechanical properties of the sample before and after the process were experimentally examined and studied. It was found that the yield and ultimate tensile strength of the AA5052 improved significantly after the first pass, while the elongation-to-failure decreased considerably. Further, the subsequent passes mildly changed the trend of increasing strength and reducing elongation-to-failure. SEM morphology indicated that the ductile mode of the initial annealed alloy changed to a combination of ductile and brittle failure modes, in which the level of the brittle failure mode increased with the addition of passes. TEM observations showed that the grain refinement during the CEC process included the formation of dislocation cell structures, subgrain boundaries, and low-angle grain boundaries, with the subgrain boundaries initially evolving into low-angle grain boundaries and, eventually, due to the imposition of additional plastic strain, into high-angle grain boundaries. Furthermore, the CEC process and its increased number of passes led to a significant improvement in wear resistance due to the enhanced tensile strength achieved through grain refinement. In this regard, the wear mechanism of the initial alloy was a combination of adhesion and delamination, with the plastic deformation bands changing to plowing bands with decreased adhesive wear during the process. Eventually, oxidization was found to be a mechanism contributing to wear under all conditions.

Improving Mechanical and Corrosion Behavior of 5052 Aluminum Alloy Processed by Cyclic Extrusion Compression

Background The severe plastic deformation approach and its well-known cyclic extrusion compression (CEC) method have been established as a powerful tool for fabricating bulk ultrafine-grained metals and alloys with improved properties. Objective This study focused on the microstructure evolution, hardness behavior, and corrosion properties of the CEC-processed Al5052 up to four passes compared to the initial annealed state. Methods The initial and CEC-processed Al5052 samples at different pass numbers were examined experimentally by EBSD analyses, hardness measurements, and corrosion resistance. Results Substantial grain refinement was attained from ~23 μm for the annealed sample to ~0.8 μm in the four passes sample. In addition, the hardness values considerably increased up to 75.7% after four passes from the initial value of 80 HV. In addition, the increment of pass numbers led to a more uniform dispersion of hardness values. Furthermore, the production of more stable protective oxide layers on the UFG structure of the CEC-processed sample led to the improvement in electrochemical response with a corrosion rate reduction from 1.49 to 1.02 mpy, respectively, in the annealed and final pass CEC-processed samples. In fact, the annealed sample manifested more large-sized and deeper pits than the CECed samples due to the increment of potential values and electrochemical attack of chlorine ions that finally deteriorates the corrosion performance. Conclusions CEC is an efficient method to improve the mechanical properties of materials due to substantial microstructural changes along with enhancement of electrochemical behavior because of the presence of small-sized and shallow pits.

Perspectives of Microstructure Refinement of Aluminum and Its Alloys by the Reciprocating Extrusion (Cyclic Extrusion Compression-CEC).

This paper presents a study on the perspectives of structure refinement of aluminum and its alloys by reciprocating extrusion (cyclic extrusion compression—CEC). The study included Al99.5 and Al99.992 aluminum and AlMg5 and AlCu4Zr alloy. Aluminum and alloys were deformed by reciprocating extrusion (CEC) in the strain range ϕ = 0.42 (1 CEC cycle) to ϕ = 59.8 (67 CEC cycles). After deformation, the structure of the specimens was investigated by optical microscopy (OM) and transmission electron microscopy (TEM), which revealed that the primary mechanism of hardening, over the range of applied strains, was the result of the propagation of shear bands throughout the specimens. The intersection of shear bands was found to divide the volume of the specimens into nano and microvolumes with dimensions limited by the width of the microbands. Due to structure renewal processes such as polygonization and dynamic geometric recrystallization, the formed micro and nano volumes were transformed into nano and micrograins with large misorientation angles. In terms of the occurrence of grain microstructure, a sustained uniform level of hardening was found, which was defined as steady-state flow. The research has shown that the steady state of flow is a result of the competitive interaction between the processes of hardening and structure renewal. The higher the metal purity, the higher the intensity of the structure renewal processes was. The formation of new grains and their growth under dynamic and post-dynamic recrystallization was observed in Al99.992 aluminum, in which high purity of the metal and high strain accumulation caused the growth of new grains at room temperature.

Hydrostatic Tube Cyclic Extrusion Compression as a Novel Severe Plastic Deformation Method for Fabricating Long Nanostructured Tubes

Hydrostatic Tube Cyclic Extrusion Compression as a Novel Severe Plastic Deformation Method for Fabricating Long Nanostructured Tubes

Processing of commercially pure copper tubes by hydrostatic tube cyclic extrusion–compression (HTCEC) as a new SPD method

Processing of commercially pure copper tubes by hydrostatic tube cyclic extrusion–compression (HTCEC) as a new SPD method

Processing and characterization of AZ91 magnesium alloys via a novel severe plastic deformation method: Hydrostatic cyclic extrusion compression (HCEC)

Capability of a novel severe plastic deformation (SPD) method of hydrostatic cyclic extrusion compression (HCEC) for processing of hcp metallic rods with high length to diameter ratios was investigated. The process was conducted in two consecutive cycles on the AZ91 magnesium alloy, and microstructural evolution, mechanical properties and corrosion behavior were investigated. The results showed that the HCEC process was successively capable of producing ultrafine-grained long magnesium rods. Its ability in improving strength and ductility simultaneously was also shown. The ultimate tensile strength and elongation to failure of the sample after the second cycle of the process were improved to be 2.46 and 3.8 times those of the as-cast specimen, respectively. Distribution of the microhardness after the second cycle was uniform and its average value was increased by 116%. The potentials derived from the polarization curves were high and the currents were much low for the processed samples. Also, the diameter of the capacitive arcs derived from the Nyquist curves was large in the HCEC processed samples. The finite element analysis indicated the independency of HCEC load from the length in comparison to the conventional CEC. HCEC is a unique SPD method, which can produce long ultrafine-grained rods with a combination of superior mechanical and corrosion properties.

Effect of grain refining by cyclic extrusion compression (CEC) of Al-6061 and Al-6061/SiC on wear behavior

Cyclic extrusion compression (CEC) is an effective fabrication process for producing fine, ultrafine grains with superior physical and mechanical properties.In the present work, CEC process was applied on Al alloy 6061 and its silicon carbide (SiCp) composite containing 5 and 10 wt. % SiCp. . The specimens were pressed at room temperature up to 6 cycles for Al alloy 6061, 5 cycles for Al 6061 5 wt. % and 4 cycles for Al 6061 10 wt. % SiC corresponding to plastic strains of 3.72, 3.1 and 2.48 respectively. The evolution of microstructure, hardness and dry sliding wear tests were conducted. The samples were investigated before and after the CEC process by optical microscope, and the worn surfaces were investigated by Scanning Electron Microscope (SEM) and (EDX) analysis. The CEC cycles reduced the grain size, porosity % and SiC particle size. These microstructural parameters were reflected on the increase in hardness and reduction in wear rate and a slight reduction in coefficient of friction. In general, this improvement in properties is associated with the following parameters; grain refining, reinforcement volume fraction, size and distribution of SiCp as well as the number of CEC cycles. Regarding the composite samples, a significant improvement in wear resistance was obtained and the Al 6061 10 wt. % SiC, showed the best performance. The wear mechanism was also affected by the CEC process.

Properties inhomogeneity of AM60 magnesium alloy processed by cyclic extrusion compression angular pressing followed by extrusion

A new severe plastic deformation (SPD) technique for improvement of the metallurgical properties of the magnesium alloys is presented. In this process, a cyclic extrusion compression angular pressing (CECAP) process is followed by an extrusion step in the outlet playing the role of additional back pressure. Therefore, more uniform and enhanced mechanical properties are expected in comparison with equal channel angular pressing (ECAP). In order to evaluate the effectiveness and capabilities of this new method, an AM60 magnesium alloy was processed. Finite element results exhibited a significant increase in strain values as well as uniform strain distribution for the new method. In addition, ~110% increase in compressive stress was observed in new method compared to the conventional ECAP. Experimental results revealed a noticeable increase in the hardness and strength of the specimens processed by the new technique as a result of the formation of finer grains and more homogeneous microstructure with good distribution of refined β-phase along the boundaries. It may be concluded that the new process is very promising for future magnesium alloy products.

Processing ultrafine grained non-circular cross-section profiles via severe plastic deformation

In this study, a new technique is presented for processing ultrafine-grained noncircular thin section profiles via severe plastic deformation. For the first time, a noncircular thin section profiles can be severe plastic deformation processed by this method entitled the noncircular thin section cyclic extrusion–compression (NCTS-CEC). In this technique, the whole length of the profile is passed through a neck zone while it is fully enclosed by the tools set. Therefore, the whole length of the specimen experiences a cyclic extrusion and compression, which accumulates a high level of strain in the material. The feasibility of the NCTS-CEC was successfully examined on aluminum profiles with L, U, and hollow square cross-sections. The microstructure evolution of the processed specimens was investigated by metallographic observations and X-ray diffraction analysis, which demonstrate the formation of a ultrafine-grained microstructure after processing by two cycles of the NCTS-CEC. Moreover, evaluations of the mechanical properties of the processed profiles show remarkable improvements in the yield and ultimate strengths. The microhardness of the processed specimens was also increased after the second cycle to ∼55 Hv from the initial value of 30 Hv. The deformation behavior of the material during processing by the NCTS-CEC method was also numerically simulated by the commercial finite element software DEFORM TM-3D V11.

Hydrostatic cyclic extrusion compression (HCEC) process; a new CEC counterpart for processing long ultrafine-grained metals

Hydrostatic cyclic extrusion–compression as a novel severe plastic deformation method in the processing of the rods is introduced and used for refining ultrafine-grained commercial pure aluminum. HCEC is solving the limitation of the conventional CEC in producing long-length samples by utilizing pressurized hydraulic fluid and eliminating the frictional effects. An increase in the length of the processable sample, a reduction in the processing loads, an intensification in the hydrostatic stress, and improvement in the strain distribution are the novel achievements of the HCEC. The capability of HCEC in grain refinement of the commercial pure aluminum was investigated by transmission electron microscopy analysis. The processed samples showed the grain sizes of 780 nm and 400 nm after the first and second passes of the HCEC, respectively. Furthermore, tensile and shear punch tests were utilized for investigation of the mechanical properties of the unprocessed and HCEC processed rods. An increase in the tensile and shear yield and ultimate strengths after the process confirmed the decreases in grain sizes. The tensile yield and ultimate strengths of the rod after the second cycle of the process reached 170 and 196 MPa, respectively. The same increasing trend as strength was shown in the microhardness after the HCEC. FEM analysis depicted the homogenous distribution of strain along the length of the sample. Also, the independency of the processing force to the length of the sample was shown by the FEM. The implementation of this novel technique looks very interesting for the industrial utilization of SPD techniques, especially in automotive and aerospace industries, which suffer from the limited size of the processing specimens.

Processing characterization of binary Mg-Zn alloys fabricated by a new powder consolidation combined severe plastic deformation method

Abstract In this paper, a new powder consolidation combined severe plastic deformation method including integrated cyclic extrusion compression (CEC), equal channel angular pressing (ECAP) and conventional extrusion was presented for processing of binary Mg-Zn alloys for biomedical applications. This research shall strive to analyze the microstructure, mechanical and corrosion properties of binary magnesium-zinc alloys with 3, 7 and then 15 wt%Zn. Upon mixing Mg and Zn powders with a variety of Zn contents, the proposed combined method was used to consolidate the mixture of powders. All alloys were thoroughly examined and demonstrated areas of partial recrystallization and high deformation. The results indicate that adding zinc to magnesium improves the mechanical properties, but these properties are deteriorated with the zinc content of over 3 wt%. The corrosion behavior of the alloy in a bio-environment was examined by immersion test, mass loss and polarization tests in Hank’s solution. The results indicate that Mg-3Zn exhibits the best corrosion resistance and the corrosion rate increases when the Zn content is more than 3 wt%. Furthermore, the samples produced through the proposed method in this work indicates better corrosion resistance in comparison with the cast and extruded pure Mg.

The Cyclic Extrusion Behavior of Severe Plastic Deformation (CEC) of Aluminum Alloy 6061

Cyclic extrusion compression (CEC) is one of the well-known techniques in metal forming processes under the severe plastic deformation process (SPD) in which an ultra-large plastic strain is imposed on a bulk material in order to make ultra-fine grained (UFG) metals, alloys and composites. In this work, the mechanical properties of the aluminum alloy (6061) before and after CEC process were examined. A special CEC die was design and fabricated for the present work which achieved an effective plastic strain of about 0.62 after each separate cycle of CEC. The microstructure was effectively refined with increasing the number of CEC cycles as the grain size was reduced from ≈250μm to ≈30 μm after 6 cycles of CEC. The mechanical properties were tremendously increased in comparison with those of as cast and annealed condition. The micro-hardness increased from 25 Hv to 56 Hv, while the yield and the ultimate tensile strengths increased from 60 MPa to 198 MPa and 85 MPa to 204 MPa respectively, the ductility increased from 2.97% to 4.6% with the number of CEC cycles increasing up to six cycles.

Processing and properties of ultrafine-grained Mg-3Al-1Zn magnesium alloy microtubes fabricated via isothermal hot microforming of SPD processed precursors

Abstract In the present paper, a new method for producing ultrafine grained microtubes of AZ31 magnesium alloy is proposed. The method consists of performing isothermal hot micro-backward extrusion on severe plastic deformation processed samples. One-pass equal channel angular pressing (ECAP) and cyclic extrusion compression angular pressing forward extrusion (CECAP-FE) were performed on an as-cast coarse-grained Mg-3Al-1Zn magnesium alloy before microtube fabrication. Microstructure and microhardness of the samples before and after micro-backward extrusion and deformation force during the fabrication process were studied. As a result, it was revealed that the proposed method performed on CECAP-FEed precursors could effectively produce ultrafine grained AZ31 magnesium alloy microtubes with excellent microhardness, good uniformity in shape, microstructure, and microhardness.

Microstructure, mechanical properties and bio-corrosion properties of Mg-HA bionanocomposites fabricated by a novel severe plastic deformation process

This research investigates the alterations in microstructure, mechanical properties, and corrosion behavior of binary magnesium-hydroxyapatite bionanocomposites with 2, 5, and 10 wt%HA. By mixing Mg and HA powders with different percentages of HA contents, a combined method of cyclic extrusion compression (CEC), equal channel angular pressing (ECAP) and conventional extrusion were employed to consolidate the mixture of powders. All composites were examined. The results indicate that the addition of hydroxyapatite to magnesium improves the mechanical properties, but these properties are deteriorated with the hydroxyapatite content of over 5 wt%. The corrosion behavior of the composites was examined by immersion test, mass loss and polarization tests in Hank’s solution. The results indicate that Mg-5HA exhibits the best corrosion resistance and the corrosion rate increases when the HA content rises to more than 5 wt%. In addition, the specimen produced through the proposed method in this work indicates better corrosion resistance in comparison with cast and extruded pure Mg.