Equal Channel Angular Processing Research Articles

DEVELOPMENT OF MICROSTRUCTURE, MECHANICAL AND WEAR CHARACTERISTICS OF THE BRASS ALLOY PROCESSED BY ECAP

In the present study, the microstructure, mechanical and wear characteristics of commercial Cu-30Zn brass alloy were developed by an equal channel-angular process (ECAP) using a particular die in constant dimensions. The ECAP process was experimentally conducted at room temperature using (1-4) passes in route C with lubricating conditions. Also, the post-annealing treatment at 350 oC has been done for some brass samples, which were deformed with four passes. Findings revealed that by conducting the ECAP, a significant reduction in the grain size of the deformed brass samples is achieved compared to the as-received alloy. The grain refinement increased with the increasing number of ECAP passes. However, the post-annealing treatment increased the grain size of the deformed brass alloy, but still it was lower than the as-received alloy. Moreover, the mechanical performance, i.e. micro-hardness and strength, was significantly enhanced after the ECAP. The samples processed with three passes presented the highest hardness value (237 HV) and mechanical strength (UTS= 692 MPa, and YS= 542 MPa) due to the homogeneous strain hardening and substantial grain refinement throughout the ECAP process. However, the micro-hardness and mechanical strength of brass alloy decreased after post-annealing treatment compared to those of the ECAP deformed samples. The elongation to failure also decreased greatly with increasing the number of passes of ECAP. Additionally, the wear resistance of the investigated samples increased significantly after increasing the number of ECAP passes compared to the as-received alloy. The highest wear resistance has been achieved for samples deformed by three and four passes of ECAP due to the considerable grain size refinement and higher hardness. However, a slight increase in the wear rate occurred after post-annealing treatment on a brass alloy sample processed with four passes due to the increase in grain size.

The impact of precipitation on recrystallization in a severely plastically deformed CoCrFeMnNi multi–principal element alloy

The present study investigated the rate-controlling mechanism for recrystallization kinetics in a severely plastically deformed (SPD) multi–principal element alloy. For this purpose, an equiatomic Cantor alloy (CoCrFeMnNi) was subjected to equal channel angular processing (ECAP) at room temperature and annealed at 773–973 K. The major recovery process was found to be concurrent recrystallization with precipitation. The recrystallization kinetics, investigated in the frame of the Johnson–Mehl–Avrami (JMAK) theory, gives a retarded recrystallization with a high recrystallization temperature of above 0.54Tm and an anomalous low JMAK exponent value of 1.1–1.8. The measured apparent activation energy for recrystallization exhibited a steady increase over the duration, with initial values of 220.8 ± 7.5 kJ/mol rising to 313.9 ± 23.8 kJ/mol towards the end. The systematic analysis leads to the conclusion that the rate-controlling mechanism for recrystallization in ECAP processed CoCrFeMnNi MPEA is the grain boundary migration-determined grain growth instead of nucleation. During this process, the Zener pinning effect exerted by precipitates from the concurrent precipitation with recrystallization plays the dominant role.

Study of Backpressure on the Composition and Characteristics of the AA5083 Alloy During ECAPed

Equal Channel Angular Processing Process at room temperature along varying backpressure level and numbers of passes produced hefty billets of 25 mm×25 mm×100 mm industrial alloy AA5083 with an ultrafinegrained microstructure. Supersaturated solid iron in an aluminium matrix was treated in brittle cast AA5083 during Equal Channel Angular Processing with Sixteen passes and a 285 MPa backpressure. The Equal Channel Angular Processing alloy’s strength, ductility, and microhardness were all greatly improved. Increased backpressure improves ductility of Equal Channel Angular Processing alloys, the workability and delays the craking of intermetallic particles. Alloys treated by Equal Channel Angular Processing have improved workability due to backpressure. The AA5083 alloy’s strength and microhardness were greatly improved. When an initially coarse-grained alloy undergoes 3 passes of Equal Channel Angular Processing with a 220 MPa backpressure, its microhardness and room strength (185 HV, UTS = 327 MPa) are significantly higher than their typical values following conventional processing with cold rolling or hot pressing. In Equal Channel Angular Processing, a super saturated solution was generated with a peak soluble of 0.6 wt.% of iron allow the ageing of the usually non-hardenable metal. The cast alloy treated using the Multi-pass approach has positively impacted toughness, elasticity, and microhardness.

Effect of CaO Addition on Microstructural Evolution Due to the Annealing of AZ31 Alloys Processed by Equal-Channel Angular Pressing (ECAP)

This study demonstrated the application of equal-channel angular processing (ECAP), which was performed via the BC route, to determine the effect of the addition of CaO on the microstructural evolution of an AZ31 alloy due to annealing. Compression tests were performed to evaluate the mechanical properties of the alloy, and the corresponding microstructures were observed to elucidate the flow behavior. Ca-bearing second-phase particles were fragmented with the increase in the number of ECAP passes. The increase in the yield strength and flow stress with the addition of CaO was attributed to the dispersion of the Ca-bearing second-phase particles. When the CaO-added AZ31 and commercial AZ31 alloys were subjected to annealing, their flow stress decreased owing to the grain growth. However, the extent of the decrease in the flow stress for the CaO-added AZ31 alloy was lower than that for the commercial AZ31 alloy.

Mechanical characterisation and microstructure study of Al-Zn alloy processed by equal channel angular pressing combined with heat treatment

ABSTRACT In the present investigation the mechanical properties and microstructural studies of heat treated and severely plastic deformed in equal channel angular processed by route ‘A’ of Al-Zn alloys were studied. The alloys were heated to a temperature of 550°C for two hours to achieve solid solution temperature before Equal Channel Angular Processing (ECAP), which improved the grain refinement. The ageing treatment at a temperature of 190°C up to 20 hours improved the precipitates which will obstruct the motions of dislocation. The experimental results revealed that yield strength and microhardness increased with increasing holding time up to 16 hr with reduced elongation due to the precipitation of GP zones and dispersion of η, ή, T and E within the Aluminium matrix. The microstructural structures revealed the three strengthening mechanisms namely dislocation strengthening, precipitation strengthening and grain refinement.

A brief overview of the equal channel angular processing approach

A possible method to create an ultra-fine grain microstructure and enhance the material's characteristics is equal channel angular pressing (ECAP). The number of variables, including the processing route, die angle, number of passes, and operation temperature, are critical in order to analyze the mechanical behaviour and microstructure of the material deformed by the ECAP process. The development of the Mg alloy microstructure and its mechanical characteristics following the ECAP approach have received particular attention. It was found that producing finer microstructure with superior mechanical properties at lower temperatures, more passes, and a smaller die angle is possible. The impact of equal channel angular pressing parameters on the mechanical characteristics and microstructure of Mg alloys is thus briefly summarised in this review paper.

Deformation mechanism finite element analysis and die geometry optimization of magnesium alloys by equal channel angular processing

Magnesium alloys are one of the highly promising structural metals. hcp structure makes it less plastic at room temperature, which greatly limits the development of magnesium alloys. The problem of poor plastic deformation of magnesium alloy can be solved by grain refinement methods, and equal channel angle pressing is one of the more effective methods in grain refinement. In this paper, two-dimensional dynamic simulation of equal channel angle pressing of magnesium alloy is carried out by using finite element software DEFORM F2™. The deformation of magnesium alloy with different of die angles and die corner angles was analyzed. The results show that in the main deformation zone, when the die angles are different, the deformation of the workpiece in the horizontal direction is very uniform. However, in the longitudinal direction of the workpiece, the larger the die angle is, the more uniform the workpiece deformation is. The die corner angle has no significant effect on the uniformity of workpiece deformation in the longitudinal direction, but it has an effect on the dead zone area and workpiece warpage. The dead zone area and workpiece warpage increase with the increase of die angle.

A study of the mechanical properties of AZ61 magnesium composite after equal channel angular processing in conjunction with machine learning

Machine-learning technique was employed in this study to investigate AZ61 magnesium alloy and its composites, in terms of predicting their microstructure and mechanical properties. This study found that, equal channel angular processing (ECAP) deformation decreases grain size and increases phase homogeneity as the number of ECAP passes increases. Microstructure observations revealed that dynamic recovery decreased with the addition of the reinforcement. The hardness values increased from 59.02 Hv at homogenized conditions to 68.9Hv following four passes of ECAP. It was also observed that hardness increased when particle reinforcement was increased. Since hardness is related to the grain size and strength, it was concluded that a decrease in the grain size improves the strength of the alloy. As a result of particle reinforcement, the composites' 0.2% yield strength and elastic modulus improved from 90.206 MPa to 94.285 MPa and from 9.499 GPa to 10.634 GPa, respectively. Using a machine learning model, it was determined that the elastic modulus and yield strength increase as the particle reinforcement ratio increases. • Interdendritic structure is formed along the grain boundaries due to the co-existence of Mg and Mg 17 Al 12. A ternary Mg 32 (Al,Zn) 49 is formed as a minor phase. • Machine learning has been used to predict mechanical properties. • Linear Regression model shows that Yield strength and Elastic moduli increase with increasing particle-reinforcement. • ECAP-deformed samples displays better mechanical properties compared to the composite (non-deformed) • Pure AZ61 Mg undergo ductile fracture while its MMCs fail by brittle-ductile fracture

Influence of Ultrafine-Grained Microstructure and Texture Evolution of ECAPed ZK30 Magnesium Alloy on the Corrosion Behavior in Different Corrosive Agents.

Magnesium-Zinc-Zirconium (Mg-Zn-Zr) alloys have caught considerable attention in medical applications where biodegradability is critical. The combination of their good biocompatibility, improved strength, and low cytotoxicity makes them great candidates for medical implants. This research investigation is focused on providing further insight into the effects of equal channel angular processing (ECAP) on the corrosion behavior, microstructure evolution, and mechanical properties of a biodegradable ZK30 alloy. Billets of Mg-3Zn-0.6 Zr (ZK30) alloy were processed through ECAP up to 4 passes of route Bc (rotating the billets 90° in the same direction between the subsequent passes) at 250 °C. Electron back-scatter diffraction (EBSD) was utilized to investigate the microstructural evolution as well as the crystallographic texture. Several electrochemical measurements were carried out on both a simulated body fluid and a 3.5% sodium chloride (NaCl) solution. Mechanical properties such as Vicker’s hardness and tensile properties were also assessed. The as-annealed (AA) microstructure was dominated by equiaxed coarse recrystallized grains with an average grain size of 26.69 µm. After processing, a geometric grain subdivision took place due to the severe plastic deformation. Processed samples were characterized by grain refinement and high density of substructures. The 4-passes sample experienced a reduction in the grain size by 92.8% compared with its AA counterpart. The fraction of high-angle grain boundaries increased significantly after 4-passes compared to the 1-pass processed sample. With regards to the crystallographic texture, the AA condition had its {0001} basal planes mostly oriented parallel to the transversal direction. On the other hand, ECAP processing resulted in crystallographic texture changes, such as the shifting of the ZK30 shear plane to be aligned at 45° relative to the extrusion direction (ED). Furthermore, the maximum texture intensity was reduced from 14 times random (AA billets) to 8 times random after ECAP processing through 4-passes. The corrosion rate of the 4-passes sample was tremendously reduced by 99% and 45.25% compared with its AA counterpart in the simulated body fluid and the NaCl solution, respectively. The pitting corrosion resistance of ZK30 showed notable improvements in the simulated body fluid by 471.66% and 352% during processing through 1-pass and 4-passes, respectively, compared with the 3.5% NaCl findings. Finally, significant improvements in the tensile strength, hardness, and ductility were also achieved.

The Role of Mandrel Rotation during CSET Processing Demonstrated on a 3003 Aluminium Alloy

Recently, the complex shearing of extruded tube (CSET) technique was proposed representing a new way of processing tubes from a bulk billet as a combination of extrusion with two passes of equal channel angular processing and possible mandrel rotation. In the present paper, the influence of mandrel rotation on the final microstructure and mechanical properties of the tube fabricated of a 3003 aluminium alloy was investigated. Electron back scatter diffraction (EBSD) revealed differences in grain size and misorientation angles between tubes processed with stationary and rotating mandrel. Kernel average misorientation maps obtained from EBSD experiments and ASTAR analysis performed in transmission electron microscopy proved differences in the dislocation density and arrangement. The tube processed using a stationary mandrel showed a recovered microstructure with elongated grains separated by low-angle grain boundaries into subgrains. The microstructure of the tube processed with a rotating mandrel was dynamically recrystallized with the grain size in submicrometer range. Vickers microhardness measurements revealed only a 40% HV increase in the sample prepared using stationary mandrel as compared with the initial billet. The mandrel rotation resulted in a much higher HV increase up to 200% as a result of substantial grain refinement.

Enhancement of strength-ductility synergy in ultrafine-grained Cu-Zn alloy prepared by ECAP and subsequent annealing

A homogeneously ultrafine-grained (UFG) Cu-38 Zn alloy with an average grain size of 0.64 μm is successfully fabricated by equal channel angular processing (ECAP), which exhibits a significantly enhanced strength-ductility synergy. The strength enhancement can be attributed to grain refinement and dislocation strengthening. After annealing the ECAP processed alloy at 300 °C for 30 min, a further enhanced strength with almost unchanged ductility was achieved. This unusual annealing strengthens is associated with the solute/impurity segregation and precipitations inside the grains.

Equal channel angular processing on aluminium and its alloys – A review

Severe Plastic Deformation is a revolutionary process for achieving ultrafine grain (UFG) material with high strength and enhanced properties. This property is acquired due to material undergoing high strain deformation without changing its shape and size. Equal-Channel Angular Pressing (ECAP) is a suggested process for SPD. Because of its versatility, Aluminium and its alloys are the most commonly used materials for a wide range of applications. This review article investigates the effects of processing Aluminium and its alloys with various ECAP die process parameters to determine their properties.

Effect of equal channel angular pressing on microstructure and mechanical performance of innovative nano MgO-added Mg-Zn-Ca composite as a biomaterial

Here, in order to implant the components in the human body, a novel composite biomaterial, the Mg-3Zn-0.2Ca composite with 0.6wt.%MgO, was processed by equal channel angular process (ECAP) with the route BC at 300℃. The evolutions of microstructure after ECAP significantly homogenized the grains. The results exhibit that the compressive strain at fracture (CSF) of the composites increased from 14.1% to 34.18% without sacrificing strength nearly. As the pass number for ECAP increasing, the added MgO and second phases turned smaller and distributed more evenly in the matrix. Meanwhile, the plastic deformation caused preferred orientation for recrystallized grains. The refinement of second phases and the variation of grain orientation by ECAP help to improve the mechanical properties of obtained composites. Furthermore, the ECAP method decreased texture density and activated more slip systems, hence the plasticity was also improved. In this study, the effects of grain refinement, microstructure homogenization, second phase distribution and grain orientation on microstructure evolution and mechanical performance during ECAP were investigated.

Development of Hot Equal Channel Angular Processing (ECAP) Consolidation Technique in the Production of Boron Carbide(B4C)-Reinforced Aluminium Chip (AA6061)-Based Composite

The production of metal matrix composites (MMCs) through recycled materials is a cost-saving process. However, the improvement of the mechanical and physical properties is another challenge to be concerned. In this study, recycled aluminium 6061 (AA6061) chips reinforced with different volumetric fractions of boron carbide (B4C) were produced through hot equal channel angular processing (ECAP). Response surface methodology (RSM) was carried out to investigate the dependent response (compressive strength) with independent parameters such as different volumetric fractions (5-15%) of added contents of B4C and preheating temperature (450 – 550°C). Also, the number of passes were examined to check the effect on the mechanical and physical properties of the developed recycled AA6061/B4C composite. The results show that maximum compressive strength and hardness of recycled AA6061/B4C were 59.2 MPa and 69 HV respectively at 5% of B4C contents. Likewise, the density and number of pores increased, which were confirmed through scanning electron microscope (SEM) and atomic force microscopes (AFM) analysis. However, the number of passes enhanced the mechanical and physical properties of the recycled AA6061/B4C composite. Therefore, the maximum compressive strength and hardness achieved were 158 MPa and 74.95 HV for the 4th pass. Moreover, the physical properties of recycled AA6061/B4C composite become denser of 2.62 g/cm3 at the 1st pass and 2.67 g/cm3 for the 4th pass. Thus, it can be concluded that the B4C volumetric fraction and number of passes have a significant effect on recycled AA6061 chips.

Evolution of microstructural deformation mechanisms under equal-channel angular extrusion loading conditions: a molecular dynamics case study of single crystal titanium

ABSTRACT Classical molecular dynamics simulations have been performed to investigate the microstructural evolution of single crystal titanium under equal channel angular extrusion process (ECAE). The ECAE loading condition has been simulated by constraining deformation along two directions and applying shear along one direction. We find that for the case where shear is applied along direction, the material yields at higher value of stress in comparison to the case where shear is applied along direction. The and twins activate for the case where shear is applied along direction and the deformation is primarily accommodated by twinning, dislocation slip and structural phase transformation. The ω-phase volume fraction increases, reaches a peak and then decreases. The decrease in ω-phase volume fraction indicates that the ω-phase is not stable. For the case where shear is applied along direction, no twinning occurs and the deformation is primarily accommodated by the dislocation slip.

Equal channel angular pressing and mechanical investigation of magnesium composite with aluminium oxide and silicon carbide as reinforcements

In this experimental analysis pure magnesium based aluminium oxide and silicon carbide reinforced hybrid composite was prepared by stir casting process. The mechanical and metallurgical properties of magnesium composite before and after equal channel angular processing (ECAP) were analysed. The scanned electron microscopy (SEM) investigation reveals about the uniform distribution of aluminium oxide and silicon carbide reinforcement particles in the magnesium matrix composite. The results show that the tensile strength of magnesium matrix composite was improved drastically by the effect of ECAP process. Further the hardness property was also increased by the incorporation of silicon carbide reinforcement particle. All these results depicts that the hybrid magnesium composite can be developed as the best material where homogeneous mixture, improved hardness and ultimate tensile strength are of primary importance in automotive and aerospace applications.

Numerical and Experimental Analyses of Equal Channel Angular Processing of Pure Aluminum

Nowadays, Equal Channel Angular Processing (ECAP) is one of the most appealing and potentially efficient Severe Plastic Deformation techniques (SPD) for fabricating Ultrafine Grained (UFG) and Nanostructured materials (NS) with sufficiently improved mechanical properties which has enabled this technique to be used in industrial applications. In this study, commercially pure aluminum was processed by ECAP through route A for up to 4 passes. A Finite Element (FE) analysis was carried out and compared to the experimental findings in order to investigate the effects of the geometric and the process’ parameters on the plastic deformation behavior of the work-piece during the ECAP process. The number of passes was selected as an input factor, while hardness values and compressive properties were modeled as the response. The total imposed stresses and strain as a function of the number of passes were examined. The FE analysis were carried out, yielding favorable results, concurring perfectly with the experimental findings and the microstructural evolution.

Optimization of ECAP—RAP process for preparing semisolid billet of 6061 aluminum alloy

6061 aluminum alloy semisolid billet was prepared by the equal-channel angular processing (ECAP)—recrystallization and partial (RAP) process (a combination of equal-channel angular processing and recrystallization and partial remelting). The effects of different process parameters on the alloy microstructure were studied and the quantitative relationship between the process parameters and microstructure was established by response surface methodology (RSM) to optimize the process parameters. According to the orthogonal test, the holding temperature and holding time of the four ECAP—RAP process parameters were found to have the greatest impact on the microstructural characteristics, including average grain size and average shape factor. Through RSM, it was also found that when the average grain size or the average shape factor is optimized separately, another will be degraded. When the two indexes were simultaneously considered, the optimal process parameters were found to be a holding temperature of 623°C and holding time of 13 min, and the corresponding average grain size and average shape factor were 35.97 µm and 0.8535, respectively. Moreover, comparing the experimental and predicted values, the reliability of the established response surface model was verified.

A Computational Investigation into the Effect of Equal Channel Angular Processing on the Mechanical Properties of Severely Deformed ZK 60 Alloy Validated by Experiments

In this study, the response surface method and finite-element analysis were employed to model the ECAP processing for biodegradable magnesium alloy ZK 60 behavior at 250°C. Using Finite-Element (FE) analysis data was extracted and compared to the what was found by experimenting in order to investigate the effects of the ECAP processing parameters on the plastic deformation behavior of the ECAPed samples. The effective strain and stresses as a function of the number of passes were investigated. Hardness contour maps perpendicular to ECAP direction were plotted. Compressive properties of the billets were also examined. The FE analysis revealed that the maximum stresses were displayed at the corner and peripheral areas compared to the central areas. Moreover, straining through two passes of route Bc displayed maximum effective strain of 2.75 recorded in the top peripheral regions, whereas the central regions displayed 1.25. In addition, ECAP processing via 2-Bc correlated with rises in Hv values in the samples peripheries by 125.4% respectively, when compared with the as-annealed conditions. The compression findings showed also significant enhancement of the compressive strength compared to the as-annealed counterparts.

Dynamic Strength of AZ31B-4E and AMX602 Magnesium Alloys Under Shock Loading

Free surface velocity histories for two magnesium (Mg) alloys are obtained from planar shock compression experiments. Symmetric plate impacts at velocities of approximately 400, 600, 800, and 1000 m/s are reported, where axisymmetric cylindrical specimens (flat-faced discs) are launched in single stage light gas guns. The studied specimens have been produced from an equal channel angular extrusion process for Mg AZ31B-4E and from a hot extrusion of consolidated powder prepared via a spinning water atomization process for Mg AMX602. The present studies focus on the region of the velocity profiles spanning the Hugoniot elastic limit through the plastic rise up to the Hugoniot state, as opposed to wave reflection, release and spall studied previously in these materials. A semi-analytical method is invoked to extract inelastic constitutive response information from particle velocity histories. The only parameters entering the procedure are fundamental thermoelastic properties—notably including elastic constants up to order three—and the ratio of plastic work to energy storage of defects generated in the crystal lattice. Plastic shock velocities are not available from the present data; these are estimated from the initial bulk modulus, its pressure derivative, and known shock velocities in conventional Mg AZ31B. Shear stress, plastic strain, plastic strain rate, temperature, and dislocation density are computed outcomes. Results demonstrate similar trends in extracted behaviors for the two alloys, whereby maximum strength in the plastic shock front increases with increasing impact velocity in each material. Strain rate sensitivity appears to be greater in AZ31B-4E than AMX602. Flow stress on the Hugoniot is calculated as 295 to 336 MPa for AZ31B-4E and 163 to 293 MPa for AMX602. Maximum flow stress in the plastic rise, as extracted from tests with maximum impact velocity, is on the order of 700 MPa for each alloy.