Equal Channel Angular Pressing Route Research Articles

Unraveling the mechanism for thermal stability of a high-strength Cu alloy produced by a novel cryogenic ECAP route

This investigation aimed to design a thermally stable microstructure of an ITER-grade Cu-0.7Cr-0.07Zr alloy. The chosen approach involved employing a novel Equal Channel Angular Pressing (ECAP) at cryogenic temperatures (CT), in which the temperature was strictly controlled, followed by subsequent ageing. Post-ECAP ageing at 400 °C for 15 min resulted in a substantial enhancement in yield strength in CT-processed specimens, with a remarkable increase of 22% in comparison to their pre-aged counterparts. Additionally, ageing under these conditions yielded a more stable microstructure at elevated temperatures, with average grain size variation below to 1 μm. The observed stability was attributed to the formation of fine Cr-rich precipitates during ageing that hinder grain boundary motion, thereby preventing grain growth and potential softening of the CuCrZr alloy. These findings elucidate a promising thermomechanical processing avenue for strengthening microstructures processed by cryogenic severe plastic deformation and/or exposure to elevated temperatures. Finally, the adopted processing route in this study not only facilitated but distinctly culminated in attaining the paramount strength/ductility relationship for CuCrZr alloys with a stable microstructure at medium-to-high temperature range.

Mechanical properties and microstructure of Al–Mg (5052) alloy processed by equal-channel angular pressing (ECAP) with variation of ECAP routes and heat treatment

Equal-Channel Angular Pressing (ECAP) has become an effective technique of severe plastic deformation designed to produce ultrafine grain metals with improved mechanical properties, such as a good combination of strength and ductility. A report on the effect of ECAP routes on the mechanical and microstructure of commercial 5052 aluminum alloy needs also to be included. This work has been undertaken, in order to obtain the results. In this work, several deformation routes were used to process the Al – Mg (5052) alloy, namely A, Ba, Bc and C. Deformation route A involved repeatedly pushing the sample into the ECAP die without rotation, route Ba was performed by rotating the sample through 90° in alternate directions between each pass, route Bc by rotating the sample 90° in the same sense between each pass and route C by rotating the sample 180° between passes. The addition of the pass number decreases the grain size of ECAP-processed samples when compared to the as-annealed sample. It also confirmed that the microstructure of the 8-pass samples shows a finer grain size than the as-annealed sample. Furthermore, the Bc route (samples rotated in the same sense by 90° between each pass) has been proven to be the most effective deformation route, in order to obtain equiaxed ultrafine grain structure when compared to other deformation routes. This phenomenon takes place due to the continuous deformation in all cubic planes. The restoration after the 4-pass number will lead to the rapid evolution of sub-grains to high-angle grain boundaries, forming equiaxed grains. The characterization of the hardness number also shows that the addition of the ECAP pass number increases the hardness number of 5052 aluminum alloy, where samples processed with the Bc route indicate the highest hardness number at 168.4 HB. Moreover, a similar phenomenon also suggests that the tensile strength of all ECAP deformation routes has comparable values. The effect of heat treatment for samples with the Bc route also shows that 200 °C annealed samples have the highest hardness number and tensile strength when compared to other samples.

Influence of ECAP Parameters on the Structural, Electrochemical and Mechanical Behavior of ZK30: A Combination of Experimental and Machine Learning Approaches

Several physics-based models have been utilized in material design for the simulation and prediction of material properties. In this study, several machine-learning (ML) approaches were used to construct a prediction model to analyze the influence of equal-channel angular pressing (ECAP) parameters on the microstructural, corrosion and mechanical behavior of the biodegradable magnesium alloy ZK30. The ML approaches employed were linear regression, the Gaussian process, and support vector regression. For the optimization of the alloy’s performance, experiments were conducted on ZK30 billets using different ECAP routes, channel angles, and number of passes. The adopted ML model is an adequate predictive model which agreed with the experimental results. ECAP die angles had an insignificant effect on grain refinement, compared to the route type. ECAP via four passes of route Bc (rotating the sample 90° on its longitudinal axis after each pass in the same direction) was the most effective condition producing homogenous ultrafine grain distribution of 1.92 µm. Processing via 4-Bc and 90° die angle produced the highest hardness (97-HV) coupled with the highest tensile strength (344 MPa). The optimum corrosion rate of 0.140 mils penetration per year (mpy) and the optimum corrosion resistance of 1101 Ω·cm2 resulted from processing through 1-pass using the 120°-die. Grain refinement resulted in reducing the corrosion rates and increased corrosion resistance, which agreed with the ML findings.

Eş Kanallı Açısal Presleme (EKAP) ile Deforme Edilen ETP Bakırın Mikroyapı ve Mekanik Özelliklerinin İncelenmesi

Severe plastic deformation (SPD), the plastic deformation of materials under high pressure, is used to improve the mechanical and structural properties of materials. Equal Channel Angular Pressing (ECAP) is one of these methods used to produce materials microstructure with submicron or nano-sized grains by applying high pressure to the sample passing through two angular intersecting channels with the same diameters. In recent years, studies on the production of nano-grained metallic materials have increased. The aim of this study is to examine the gradual change of the microstructure and mechanical properties of the material under high pressure and to determine the effect of ECAP on the improvement of these properties. This process is directly related to the internal structure and texture of the material. With the applied method, it is aimed to obtain a more durable material structure. Electrolytic Tough Pitch (ETP) copper material, which is one of the copper types commonly used in electrical applications, was chosen in the study. 12 mm diameter and 35 mm long ETP copper samples, which were not subjected to any heat treatment, processed on 2 mm/s pressing speed, 200°C mold temperature and Bc ECAP route using a 120 ton capacity hydraulic press, a precision machined mold which has 120° (Φ=120°, ψ=20°) channel angle. The changes in the crystal structure, microstructure and mechanical properties of the ECAP applied samples were investigated. According to the data obtained, it was observed that the 4 passes of ECAP application resulted in having finer grains in microstructure and improvement in mechanical properties.

Modeling of texture evolution in copper under equal channel angular pressing

Abstract Texture evolution was analyzed with the full-constraint Taylor model for an idealized perfectly plastic face-centered cubic material as well as for real, strain-hardening copper subjected to equal channel angular pressing (ECAP). For the idealized material, the stress in the plastically deformed part of the billet was shown to be uniform leading to complete filling of the die. Finite element simulations showed that plastic deformation is localized in a narrow shear zone and that the plastic strain and texture in the billet become uniform after ECAP. A simplified recipe for texture calculation akin to that proposed by Gholinia et al. was suggested: it reduces the deformation under ECAP to a combination of two rotations separated by tension-compression. For the case of copper, a strain hardening model based on dislocation density evolution was used. It was shown that due to significant strain hardening during the first ECAP pass, the flowing material does not fill the outside die corner and a strain and texture non-uniformity develops. A gradual decrease of the strain hardening in subsequent ECAP passes leads to a more uniform strain and texture across the billet. The simulated pole figures were shown to be in good agreement with the neutron diffraction data for copper deformed by ECAP (Routes A, Cr, Bγ and Bcr) suggesting that the model used provides a reliable modeling tool for simulating texture evolution under ECAP.

The mechanical property and electrical conductivity evolution of Al–Fe alloy between room temperature and elevated temperature ECAP

Ultra-fine grained Al–Fe alloy rods were manufactured by Equal-channel Angular Pressing (ECAP) at the two temperatures (room temperature (RT) and elevated temperature (ET)). Microstructure, mechanical properties, and electrical conductivity exhibited an abnormal evolution between RT-ECAP and ET-ECAP. A strong dissolution of micron Al3Fe and Al6Fe precipitations has been demonstrated in this immiscible Al–Fe alloy systems at such a few strains during the ET-ECAP. The Fe solid atoms dissolved back into the matrix, induced high-density dislocation and accelerated the grains refinement. It contributed to the finer grains, higher strength as well as dramatic decreased electrical conductivity in ET-ECAP. Meanwhile, the agglomeration and growth of nanoparticles decreased its dispersity in matrix distribution in RT-ECAP, leading to strength in RT-ECAP shown a stable or even decrease tendency, while strength constantly grew in ET-ECAP. Based on the feature of dissolution and precipitation, a high strength combined with a considerable electrical conductivity of this investigated Al–Fe alloy has been simultaneously achieved by the modified ECAP routes using 4 ECAP passes at room temperature and then another 4 passes at elevated temperature. The yield stress (~178.0 MPa) and electrical conductivity (~61.55%) are superior to the convention ECAP routes of 8 RT-ECAP passes and 8 ET-ECAP passes.

Optimization of Equal Channel Angular Pressing Parameters for Improving the Hardness and Microstructure Properties of Al–Zn–Mg Alloy by Using Taguchi Method

In this study, optimization of equal channel angular pressing (ECAP) parameters was aimed to improve the mechanical and microstructure properties of Al–Zn–Mg alloy using the Taguchi method with ANOVA analysis. Three different parameters (process temperature, processing route, and the number of passes) with three different levels were examined so L9 (33) orthogonal array was employed. The effects of these parameters on the microstructure properties of Al–Zn–Mg alloy were studied using X-ray diffractometer, optical microscopy, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy and mechanical properties were measured by Vickers micro-hardness experimental tests. Among the samples obtained, the sample that meets the desired hardness and grain size value was characterized. The results indicate that eight pass ECAP in route Bc at 100 °C is found as a more appropriate condition that meets the highest micro-hardness value and the lowest grain size value. Microstructural investigations showed that grain size was highly affected by the temperature, and is less affected by the number of passes and ECAP routes. The results showed that the increasing ECAP temperature leads to a decrease in the fraction of HABs, an increase in the grain size and an increase in the equiaxed of the grains.

Effects of different deformation routes of ECAP on AA6063 mechanical properties and microstructure

In order to investigate the influence of different deformation routes of equal channel angular pressing (ECAP) on mechanical properties and microstructure of AA6063 alloy at room temperature. The specimens were processed with angle of 120°regarding processing routes A, BA, BC, BC-UD2 and C. Then the macro morphology of specimens was analyzed, the strength and hardness were measured, and the microstructure was observed by SEM. The results show that, after four passes, the deformation of route A is the most inhomogeneity, while route BC-UD2 is the most homogeneity. Route BC deformation is relatively uniform and not easy to generate cracks on up-surface. The increase of tensile strength of route BC and route C is the most. The ductility of route BA and route BC keep best. Route BC can not only improve the strength of the material, but also maintain the plasticity of the material. The hardness improvement and the deformation uniformity show negative correlation under in all routes. The hardness improvement is most obvious after route BA, and the deformation is most homogeneous after route BC-UD2. The microstructure of route C and route BC is equiaxed grain. The average grain size of specimens is smaller after route C.

Friction stir extrusion to recycle aluminum alloys scraps: Energy efficiency characterization

Solid state recycling refers to a group of processes allowing direct recycling of metals scraps into semi-finished product. Their main advantage lies in avoiding the molten state of the material which badly affects the environmental performance of the conventional (remelting based) recycling routes. It is expected that such process category would lower the environmental performance of metals recycling. In this paper, the friction stir extrusion process for aluminum alloy AA 2050 wire production is analyzed under the primary energy demand perspective. The process electrical energy demand is quantified with varying process parameters. An empirical modelling approach was applied and an analytical model able to expresses the specific energy consumption as a function of the extrusion rate was carried out. Finally, the primary energy demand of the whole recycling route was quantified and compared with both conventional and Equal Channel Angular Pressing (ECAP) based routes. Results revealed that Friction Stir Extrusion approach allows substantial primary energy savings for the case of wire production. To be more specific, FSE allows a reduction in energy demand up to 74% and 63% with respect the conventional and the ECAP routes, respectively. This is mainly due to avoided permanent material losses as well as to the absence of intermediated process steps (wire drawing).

Can zinc alloys be strengthened by grain refinement? A critical evaluation of the processing of low-alloyed binary zinc alloys using ECAP

In this work, the effect of equal channel angular pressing (ECAP) on the microstructure and mechanical properties of zinc and zinc alloys with Ag, Cu, and Mn additions (0.5 at%) was investigated. Four passes of ECAP Route BC was performed at room temperature for each material. Properties of investigated materials after ECAP were compared to their coarse grained counterparts obtained via indirect hot extrusion at 300 °C. Highest strengthening effect was observed for alloy containing the Mn addition. Grain refinement in materials after ECAP was obtained, mean grain diameter is equal to 20 µm in the case of pure zinc, and less than 3.2 µm for alloys. Strain rate dependent plasticity increase was observed for all fine grained materials, with maximum elongation of 510% measured for Zn-Cu alloy after ECAP. Grain refinement did not result in increased yield and ultimate tensile strength of alloys after ECAP. In all investigated materials tensile properties after ECAP were 20 ~ 60% lower than in hot extruded samples. Based on the tensile properties, microstructure and texture analysis, the changes in the main deformation mechanisms were considered. It was presented that the crystallographic texture and grain size are the main factors affecting twinning, slip and non-slip deformation mechanisms resulting in large differences in observed mechanical properties.

Effect of the equal channel angular pressing route on the microstructural and mechanical behavior of Al-5086 alloy

The present paper analyzes the effect of the equal channel angular pressing (ECAP) routes A and Bc on the recrystallization conditions and mechanical properties of Al-5086 alloy. The specimens were processed up to 10 passes at 150 °C in a die with 120° inner angle. The recrystallized grains developed after the tenth pass in the route A. By increasing the number of passes the grains became finer and after the tenth pass, the average grain size became finer than 2 µm. The tensile and hardness tests results showed that in all passes, the route Bc had a stronger effect on the simultaneous improvement of strength and ductility. The fracture surfaces analyses showed that the local ductile behavior improves as increasing the number of passes. The textures analyses showed that the dominant component was altered from (111) to (200) and (220) plane by increasing the number of passes through both routes. Also, the dislocation density increased by increasing the number of passes.

Exploration of equal channel angular pressing routes for efficiently achieving ultrafine microstructure in magnesium

This research explored the equal channel angular pressing (ECAP) routes for efficient microstructure refinement of pure magnesium. The samples were processed for a series of numbers of ECAP passes through three different routes (i.e. A, Bc, and C routes). The utilized ECAP mold had a large channel angle of 142° and the processing temperature was 200 °C. The microstructure and texture of the processed samples were characterized using optical microscope and x-ray diffraction technique. The results show that tension twinning deformation mechanism during an ECAP pass led to the formation of profuse twins in magnesium and the twinning/detwinning dominated microstructure refinement mechanisms. After 8 ECAP passes, both Bc and C routes reduced the length and width of twins to ~ 13 µm and ~ 3 µm respectively. Bc and C routes can refine the microstructure of magnesium more efficiently than A route. Among the three studied routes, Bc route achieved the most homogeneous microstructure with uniformly distributed twins, while both A and C routes resulted in heterogeneous microstructure.

Effect of Different Processes on Hydrogen Storage Properties of AZ Magnesium Alloy

In this research, AZ31 and AZ91 magnesium alloys were used as hydrogen storage materials to compare the effects of equal channel angular pressing (ECAP) and high energy ball milling (HEBM) processes on the hydrogen storage properties. In addition, the effects of using different AZ magnesium alloys (AZ31 and AZ91) with the same processes and parameters on the hydrogen storage properties were investigated. The results show that the crystal size of AZ magnesium alloy has been decreased by both ECAP and HEBM processes. It was also revealed that AZ31 magnesium alloy processed by ECAP route BC with 8 passes has faster absorption and desorption rate than AZ31 magnesium alloy processed by HEBM ball material ratio 30:1 with 300rpm. The capacity of two samples is 7.0 and 6.8 wt.%. The AZ91 magnesium alloy processed by HEBM ball material ratio 30:1 with 300rpm has faster hydrogen absorption and desorption rate than that of AZ91 magnesium alloy processed by ECAP route BC with 8 passes at 375oc. The capacity of two samples is both 6.7 wt.%.

Workability Limits of Magnesium Alloy AZ31B Subjected to Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) is an important severe plastic deformation process to produce ultrafine grained microstructures in metals and alloys. Magnesium and its alloys generally possess poor workability at temperatures below 250 °C. This investigation examines the influence of different passes and processing routes of ECAP on improving the workability of Mg alloy AZ31B. ECAP was carried out for three passes using a die of angle 120° using processing routes Bc and C. The operating temperature was 523 K for the first pass and 423 K for the subsequent two passes. The resultant microstructure and mechanical properties were determined. Workability of the alloy at 423 K (150 °C) was determined using upsetting experiments on cylindrical specimens machined from the annealed and ECAPed samples. Workability limit diagrams have been constructed for the various processed conditions. The workability data generated were also analyzed using five different workability criteria (also referred to as ductile fracture models) and the material constants for these five models were evaluated. Specimens processed by two passes through route C (pass 2C) exhibits better workability compared to other passes since the workability limit line after this pass shows maximum safe working area and lies above the other workability lines. Among the five different workability criteria investigated, the Freudenthal workability criterion is more suitable for prediction of failure in this alloy.

Effect of equal channel angular pressing (ECAP) on hydrogen storage properties of commercial magnesium alloy AZ61

Cast commercial AZ61 magnesium alloys were processed through equal channel angular pressing (ECAP) and were comminuted into chips by filing with a rasp in order to measure their hydrogen storage properties. The effects of the number of ECAP passes and the processing route of ECAP on the hydrogen storage properties of AZ61 magnesium alloys were investigated. ECAP processing led to severe dynamic recrystallization and grain refinement of the AZ61 alloys. Of the analyzed samples, the AZ61 alloy processed via the Bc ECAP route with eight passes exhibited the smallest grain size, the fastest hydrogen absorption and desorption rates, and the highest gravimetric hydrogen storage capacity of 6.2 wt%.

Improving hydrogen storage performance of AZ31 Mg alloy by equal channel angular pressing and additives

In this study, commercial AZ31 Mg alloys were processed by equal channel angular pressing (ECAP) to study the effects of processing route and numbers of passes on hydrogen storage properties of AZ31 alloys. Furthermore, Mg-based metal matrix composites (MMCs) were fabricated by gravimetric casting of AZ31 alloy, activated carbon and Ni to investigate the effect of additives on hydrogen storage properties. The results indicated that kinetics of hydrogen uptake increased with the increasing number of pass. AZ31 processed by ECAP route Bc with 8 passes had hydrogen capacity of 7.0 wt%, and demonstrated the highest grain refinement and the fastest hydrogen absorption kinetics. With the addition of 5 wt% of activated carbon and 0.5 wt% Ni, the hydrogen sorption kinetics of MMCs was enhanced and was comparable to that of the AZ31 processed by ECAP with 8 passes; however, in exchange for the improved kinetics, the hydrogen storage capacity was lowered to 6.3 wt%. To enhance hydrogen absorption kinetics, adding catalysts in the casting process could be more efficient than post-casting ECAP treatment if saving processing time is the priority.

Combined effects of ECAP and subsequent heating parameters on semi-solid microstructure of 7075 aluminum alloy

The combined effects of equal channel angular pressing (ECAP) and subsequent heating to a semi-solid temperature on the microstructural characteristics of the 7075 aluminum alloy were investigated. The microstructure is influenced by several parameters including the number of ECAP passes, ECAP route, consequent heating temperature, and holding time. The effects of these parameters on the microstructural characteristics including grain size and shape factor of the 7075 aluminum alloy were studied using experimental tests and Taguchi method. The results indicate that five-pass ECAP in route BA and subsequent isothermal holding at 630 °C for 15 min are more appropriate for achieving a semi-solid microstructure. The processing route and holding time have the highest impact on the grain size while the number of ECAP passes and heating temperature have the least impact on the grain size. Meanwhile, the shape factor is significantly influenced by the processing route, holding time and heating temperature while it is less influenced by the number of ECAP passes.

Influence of equal channel angular pressing routes on texture, microstructure and mechanical properties of extruded AX41 magnesium alloy

The influence of three different equal channel angular pressing (ECAP) routes (A, Bc and C) on the grain size, texture, dislocation structure and mechanical properties in pre-extruded AX41 magnesium alloy was investigated. It was found that during the first passes, the rate of grain fragmentation strongly depends on the processing route. After 8 passes, despite the almost identical values of the dislocation density (0.7×1014m−2), the average grain size varied in the range of 2.0–4.5μm for the individual ECAP routes. Macroscopic texture measurements revealed a gradual formation of very strong textures, which were significantly different for the various processing routes. The strength and the ductility of the samples were investigated by tensile test carried out parallel to the outgoing channel axis. Route A was found to be the most effective processing route for grain refinement. In tensile tests carried out at room and elevated temperatures, the highest strength was observed for the sample processed via route A for 8 passes, due to the highest texture hardening and the smallest grain size.

Study on structure homogeneity of plate sample with large dimension during equal channel angular pressing (ECAP)

Abstract

Effect of Processing Parameters on the Magnetic Properties and Macrotexture of a Nd13.5Fe73.8Co6.7B5.6Ga0.4Alloy Processed by Equal Channel Angular Pressing With Back Pressure

Equal channel angular pressing (ECAP) is a well-established thermo-mechanical processing technique, which could induce the $c$ -axis texture of Nd2Fe14B in a melt-spun Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy. However, the effects of ECAP processing parameters, such as temperature, back pressure (BP), and multiple-pass ECAP routes, remain unknown for this alloy. In this paper, we have investigated the effects of these processing parameters on the $c$ -axis texture formation. It is found by X-ray diffraction macrotexture analysis that the maximum intensity of (001) pole figures for the tetragonal-Nd2Fe14B phase ( $I_{\max }$ ) shows an increase from 2.7 to 4.1 m.r.d. (multiples of random distribution) by increasing the ECAP temperature from 723 to 823 K, while the difference in remanent magnetization between easy and hard directions ( $\Delta M_{r}$ ) rises from 24.0 to 41.5 Am2/kg. When the BP was increased from 0.25 to 0.5 GPa at 823 K, $I_{\max }$ showed an increase from 2.8 to 4.1 m.r.d. However, $I_{\max }$ saturated for BPs above 0.5 GPa, suggesting that BP has limited effect on the texture formation, although it is necessary for the compaction of the alloy powders. Two multiple-pass ECAP routes conventionally known as routes A and C were employed for two-pass ECAP at 823 K. It is found that route A processing is effective in enhancing the texture formation, while the texture is lost by a subsequent pressing when adopting route C. Therefore, the compaction of Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy powder using route A ECAP passes with 0.5 GPa BP at 823 K results in pronounced texture, which is beneficial for anisotropic hard magnetic properties.