Search

The main goal of this research is to scrutinize the effect of texture and grain size on the biological response of hierarchical structured pure titanium (Ti), examining the interrelation between grain refinement mechanisms with texture variation. The hierarchical structure was produced using two methods of severe plastic deformation (SPD). The Ti specimens were first processed up to six passes by equal channel angular pressing (ECAP) and subsequently treated at the top surface using surface mechanical attrition treatment (SMAT). Microstructure examination by Electron backscatter diffraction (EBSD) indicates that the SMAT-treated surface was categorized into three distinct microstructural regions based on the type of grain refinement process involved during SPD: twin induced dynamic recrystallization (TDRX) and geometric dynamic recrystallization (GDRX) in the topmost surface, and continuous (CDRX) and discontinuous dynamic recrystallization (DDRX) in the lower regions of the sample. The biological experiments showed meaningful improvement in the cellular response of SMATed and ECAPed samples. It was demonstrated that grain refinement could have the capability of improving the biological response of Ti surface. In this regard, SMATed + 2ECAPed sample showed the best result although it has not the smallest grain size and the highest texture intensity. It was observed that texture and grain orientation of planes have an important impact on the biological response of pure Ti and dominance of prismatic (1010) texture can improve the cell viability, adhesion and its differentiation. Therefore, microstructure and texture tailoring through combined SPD methods could be a promising strategy for the improvement of the next generation of medical implants.

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure, mechanical, and erosion-corrosion behavior of commercial pure (CP) titanium was investigated through experimental work. Four passes of ECAP processing at 400 ℃ was performed on CP titanium. The results showed that the homogeneous structure and coarse equiaxed grains of the initial annealed sample are transformed into the combination of UFG and NS with an average size of 750 nm and 85 nm, respectively. Also, ECAP pass numbers increase the fraction of high angle grain boundaries which improves the ductility of the processed sample. The highest hardness and strength improvement rate was observed after the first pass. Furthermore, the increasing rate of hardness and strength is gradually decreased at the subsequent passes and reached the steady-state level at the 4th pass. This is due to the balance between hardening by dislocations and twinnings accumulation and softening by recovery mechanisms. As a result, a uniform hardness distribution on both the cross-sectional and longitudinal planes is achieved. It was confirmed that erosion-corrosion resistance of the processed sample is enhanced due to the grain refinement, material homogeneity, and quick formation of a strong oxide bond layer on the surface.

Titanium and its alloys are used in several industries, especially in medical and dental applications. In the present study, the surface properties of nanostructured commercially pure titanium (CP-Ti) and its erosion–corrosion (E–C) behavior in simulated body fluid were studied. Equal-channel angular pressing (ECAP) was performed at a high temperature (400 °C) to produce nanostructured grain samples of CP-Ti. Then, the effects of ECAP passes on the E–C resistance under various conditions were investigated via weight loss measurements. Optical microscopy and transmission electron microscopy observations were performed to investigate the microstructural changes of the material. The surface roughness of the CP-Ti samples was evaluated using an optical profiling system. Mathematical equations of the modified Finnie model were employed for the analytical analysis of the E–C behavior. Additionally, computational fluid dynamics was utilized to model the E–C behavior of CP-Ti. Overall, the results showed that the ECAP process improved the E–C resistance of CP-Ti. A difference of 12 pct was observed between the experimental and numerical results of E–C resistance, which is acceptable for practical applications

In this study, the flow-forming process for fabricating seamless thin-wall tubes is experimentally investigated on a commercially pure titanium sample. For this purpose, the influence of three processing parameters including feed rate, mandrel revolution, and thickness reduction is studied on the surface quality and geometrical accuracy of flow-formed tube. It is found that the feed rate increment results in more longitudinal displacement of the roller on the tube sample. This intern results in, more area of the material to be in contact with the roller during the tube revolution; hence, higher tube surface roughness. Also, surface finish and dimensional precision of spun tube are lessened by increment of the mandrel revolution due to the intensification of machine vibration. Additionally, increased reduction of wall thickness leads to the enlargement of diametral growth and the loss of roundness. Also, it will increase the resistance of the material flow, which results in the wave creation at the tube surface, thereby decreasing the surface quality of the spun sample.

Improvement of equal channel angular pressing (ECAP) efficiency is an important challenge for industrialization of this technique. The reduction of pressing load and improvement of material mechanical properties are among the most challengeable subjects during this process. In this research, commercial pure aluminum has been ECAPed at room temperature using conventional and ultrasonic vibration techniques to investigate the influence of ultrasonic wave on the pressing load and mechanical characteristics of deformed samples. The results showed that the superimposing ultrasonic vibration on the ECAP process not only decreases the required punch load, but also improves the mechanical properties of the material as compared to the conventional condition. Interestingly, the ultrasonic vibration assisted process leads to about 16%, 10% and 12% increments at the yield strength, ultimate tensile strength and hardness value respectively and also, 9% reduction at the punch load. Furthermore, the dislocation density of the sample produced by ultrasonic assisted ECAP is about 35% more than the achieved conventional sample.

To date, ECAP technique have been successfully employed to produce Ultra-fine/Nanostructure grain materials, but some materials such as hexagonal closed-packed (HCP) alloys are difficult to process by ECAP at room temperature. In this work, Transmission Electron Microscopy (TEM), Vickers hardness test and Torsion test were employed to confirm the attainment of ultrafine/nanostructured grain (UFG/NSG) commercial pure titanium (CP-Ti) Titanium fabricated by ECAP as a sever plastic deformation process. The samples were pressed by ECAP (route BC) up to four passes at elevated temperature (400° C). Finally, the Erosion-Corrosion (E-C) behavior of ultrafine/nanostructured grain (UFG/NSG) Titanium in a simulated body fluid were investigated through weight loss measurement.

To overcome some possible deficiencies of pure copper, dilute alloying and employment of equal channel angular pressing seem the cost-effective solutions. In this work, dilute copper alloys with the tin amount of 0.18, 0.3, and 0.5 wt.% were obtained with continuous casting and subsequently, they were subjected to ECAP process up to four passes. It was shown that integrated treatment by dilute alloying and ECAP lead to 182% improvement of the corrosion resistance as compared to the as-received condition due to the grain refinement. Meanwhile, the alloying impact on current density is decreased with the ECAP process which may result from the changes at the distribution of Sn atoms in Cu. The difference in measured corrosion current density of unprocessed and ECAPed samples for the alloys Cu-0.3%Sn and Cu-0.5%Sn are 15% and 2%, respectively. The corrosion improvement by means of current density reduction due to the alloying before the ECAP process is about 45% while this value after the ECAP diminishes to 35%. Microstructure analysis showed that four passes of ECAP process cause the average grain size of the pure copper to less than 700 nm and the Cu-0.5%Sn to about 550 nm. Also, the HAGBs fraction of the ECAPed pure Cu is 74%, while the corresponding magnitude for the Cu-0.5%Sn is 78%. © 2019 Politechnika Wrocławska

The last decade has witnessed considerable advancements in nanostructured material synthesis and property characterization. However, there still exists some deficiency in the mechanical and surface property characterization of these materials. In this paper, the erosion corrosion (E-C) behavior of nanostructured copper was studied. The nanostructured copper was produced through severe plastic deformation (SPD) by applying four passes of equal channel angular pressing (ECAP). The combined effects of the testing time, impact velocity, and concentration of erosive solid particles (i.e., sand concentration) on the E-C behavior of nanostructured copper were then examined. Based on a defined domain for the testing time, impact velocity, and sand concentration, E-C tests were performed for numerous combinations of test points via the slurry pot method. The test points were selected using the face-centered center composite design of experiments to enable visualization of the test results through surface plots. The extent of E-C on the test specimens was determined by measuring the mass loss. Polynomial regression and Kriging were used to fit surfaces to the experimental data, which were subsequently used to generate surface plots. The results showed that the E-C of nanostructured copper is best described by a quadratic function of testing time, velocity, and erosive solid particle concentration. The results also revealed that E-C increases with an increasing testing time, impact velocity, and erosive solid particle concentration. In addition, it was observed that the effect of the erosive solid particles on E-C is further intensified by an increased impact velocity.

Among severe plastic deformation methods, groove pressing is one of the prominent techniques for producing ultra-fine grained sheet materials. This process consists of imposing repetitive severe plastic deformation on the plate or sheet metals through alternate pressing. In the current study, a 2 mm pure Cu sheet has been subjected to repetitive shear deformation up to two passes. Hardness and tensile yield and ultimate stress were obtained after groove pressing. Fracture toughness tests have been performed and compared for three conditions of sheet material namely as received (initial annealed state), after one and two passes of groove pressing. Results of experiments indicate that a decrease in the values of fracture toughness attains as the number of constrained groove pressing (CGP) passes increase.

Ultrafine Grained (UFG) and Nano-Structured (NS) materials have experienced a rapid development during the last decade and made profound impact on every field of materials science and engineering. The present study has been undertaken to develop ultrafine grained pure copper by severe plastic deformation method and to examine the impact property by different characterizing tools. For this aim, equal channel angular pressing die with the channel angle, outer corner angle and channel diameter of 90°, 17° and 20 mm, respectively had been designed and manufactured. Commercial pure copper billets were ECAPed up to four passes by route B C at the ambient temperature. The results indicated that there is a great improvement at the hardness measurement, yield strength and ultimate tensile strength after ECAP process. It is found that the magnitudes of HV reach 136 from 52 HV after the final pass. Also, about 285 and 125% enhancement at the YS and UTS values have been obtained after the fourth pass as compared to the as-received conditions, respectively. On the other hand, the elongation to failure and impact energy have been reduced by imposing ECAP process and pass numbers. It is needed to say that about 56% reductions in the impact energy have been attained for the samples as contrasted to annealed specimens. Furthermore, the grain size of the final pass is 800 nm for Cu sample. Finally, fracture surfaces of billets after impact test have been investigated using Scanning Electron Microscope (SEM).

A new development of equal channel angular pressing method to fabricate wire-formed samples has been proposed and experimented. In this approach, wire-formed specimen, which is inserted inside a polyurethane rubber pad material, has been pressed using conventional equal channel angular pressing die. Commercial pure copper samples in the shape of wire have been equal channel angular pressed up to 12 passes by route BC, and then hardness behavior, electrical conductivity and microstructure observation of deformed samples have been examined. The results indicate that about 77% and 66% enhancements at the hardness value (HV) magnitudes have been obtained after 8th and 12th passes, respectively, as compared to the unequal channel angular pressed state. Reductions of about 92% and 95% at the grain size of pure copper have been observed after 8th and 12th passes, respectively, in comparison with the annealed condition. Also, the first pass of equal channel angular pressed wire has both the worst hardness distribution homogeneity and the lowest electrical resistivity. On the other hand, the final pass of pressed wire has both the best hardness dispersal uniformity and the highest electrical resistivity.

Commercially pure titanium was processed by equal channel angular pressing (ECAP) and surface mechanical attrition treatment (SMAT) for the purpose of developing functionally graded titanium used for implants and a gradient structure including nanostructured, deformed and undeformed zones were produced on the samples. In particular, it was aimed to design the gradient-structure in the titanium with enhanced properties by applying 4 ECAP passes to form bulk structure of ultrafine-grains and subsequently subjecting SMAT to the surface of ECAPed samples to produce nanostructured surface region. Microstructural examination was made by electron back scatter diffraction (EBSD). Also, microhardness, nanoindentation, topography, roughness and wettability were evaluated. To examine the biological response, human osteosarcoma cells were cultured in contact with the samples in various time periods and morphology change, cell viability and alkaline phosphate activity were conducted also cell morphology was monitored. EBSD showed development of ultrafine-grained structure after 4 passes of ECAP with an average grain size of 500 nm. Applying SMAT resulted in additional refinement in the ECAP samples, particularly in the subsurface regions to a depth of 112 μm. Furthermore, the SMATed samples showed an enhancement in roughness, wettability and hardness magnitudes. Viability enhanced up to 7% in SMATed + ECAPed sample, although the acceptable cell adhesion, improved cell differentiation and mineralization were seen. The combined use of ECAP and SMAT has shown a good potential for optimizing the design of modern functionally graded medical devices and implants.

A new technique to produce ultra-fine grained tubular specimen has been proposed, and the experiments have been performed using equal channel angular pressing (ECAP) with an angle of 90° between two intersecting channels and also the use of rubber pad as a mandrel during process. Commercial purity copper tubes have been pressed up to three passes through four different fundamental routes (A, BA, BC, and C) directions of which are identified in the text below. The influence of each route on the value, distribution, and homogeneity of hardness has been investigated by applying Vickers micro-hardness measurements at various locations of the tube’s transverse planes. Significant enhancement of the hardness is observed after the first pass ECAP. Also, routes C and BC show, respectively, better average hardness magnitude and hardness distribution uniformity. In addition, the results indicate that there is about 50% and 62% reduction of the grain size, compared to the annealed condition, following ECAP process of the copper tube sample after the first and the third pass via route BC.

Constrained groove pressing (CGP) process is one of the favorable severe plastic deformation methods to fabricate ultra-fine grain sheet materials. In this paper, commercial pure aluminum sheet was subjected to CGP process using conventional and covered sheet casing (CSC) methods. Three dies with different groove lengths and angles ( t = 1 mm and θ = 45°; t = 1.8 mm and θ = 45°; t = 1 mm and θ = 53°) were designed and manufactured. Mechanical properties including strength, elongation to failure and hardness are obtained and discussed. The influences of these two methods and die groove angle on specimen strain behavior and required force value are analyzed by the finite element method in plain strain condition. The results show that the CSC method leads to better hardness distribution, uniform strain dispersal and finer surface quality as compared to conventional method. Moreover, the new method is a good candidate for substituting the conventional CGP process.

Suitability of AA2024-T3 and AA5083-H111 aluminium sheet alloys for forming operations in room temperature were examined by using forming limit diagrams with different strain paths. In the experimental part, circular bulge, non-grooved tensile as well as grooved tensile specimens were used. This was done to simulate the following: (a) biaxial stretching region (positive range of minor strain), (b) uni-axial strain path and (c) strain path from uni-axial tension to plane strain region of the forming limit diagram, respectively. The effects of combined strain paths coupled with material anisotropy were taken into account in each stage. Tensile properties as well as formability parameters were correlated in accordance with the attained forming limit diagrams. Average plastic strain ratio and planar anisotropy, in addition to work hardening exponents of the samples, were calculated from the test data and the effects on the forming limit diagrams were discussed. Moreover, comparisons were made between experimental and theoretical forming limit diagrams. It is shown that experimental forming limit diagrams are in very good agreement with the theoretical predictions, particularly when BBC2000 yield criteria are used for the M–K model. In addition, theoretical prediction by using the Hill93–Swift model showed small deviation with the experimental forming limit diagrams. Finally, finite element simulations were carried out to investigate the numerical forming limit diagrams through an industrial sheet metal forming simulation software. It was consequently shown that, due to frictional effects resulting from hemispherical-shaped punch, the finite element results depicted small deviation compared to the experimental data.

Equal channel angular pressing as a material processing technique imposes high but in-homogeneous strain at the cross-section of the workpiece. In this research, cylindrical shaped commercial pure aluminum undergoes ECAP process up to four passes by route A using the conventional and covered tube casing (CTC) methods. The influence of CTC on strain distribution in the region of uniform longitudinal strain field was investigated experimentally and numerically. The Vickers hardness measurement at the cross-section of the aluminum samples indicated that there is more uniformity in the deformation during a single-pass ECAP in the CTC method compared with the conventional method and matched the simulated effective strain distributions. Moreover, based on volume fraction rule, an analysis has been developed to predict the required pressing force for CTC method.

A simplified sheet hydroforming tooling was designed, fabricated, and tested. The advantage of the new tooling is its simplification of the tools, its requirement of lower hydraulic pressure for forming and decreasing the cost of the process. In this article, a new method of hydroforming deep drawing assisted by floating disk is proposed and investigated through experiments and simulation. Moreover, its advantages, such as simplifying the tools, decreasing the required medium pressure of the forming process, and elimination of some wrinkle due to ironing effect, have been discussed. An aluminum alloy, Al6061-T6, is formed successfully, and the influence of process parameters including the punch nose radius and friction are studied. It is determined that decreasing punch radii and friction, lead to a decrease in initial pressure and an increased safe zone, respectively. Working pressure curves, which guarantee sound workpieces, have been founded by series of experimental results. Wrinkling and fracture mod...

Microhardness homogeneity was assessed on commercial pure titanium processed by equal channel angular extrusion (ECAE). The operation was performed with die channel angle of 90° and processing temperature of 450 °C by route BC up to six passes. The Vickers microhardness measurements were investigated on both cross-sectional and longitudinal planes of the annealed, one-, two-, four-, and six-pass ECAEed titanium. It was found that the application of the process and the addition of pass numbers lead to the improvement of hardness magnitude. It was shown that there are some areas of microhardness heterogeneity in surrounding and bottom regions of the one-pass and two-pass specimens at the cross-sectional plane which is slightly disappeared by adding the pass numbers. Furthermore, there is a suitable amount of hardness homogeneity in the longitudinal plane, irrespective of the specimen condition. It can be concluded that a desirable homogeneity of hardness can be attained after imposing six passes of ECAE process on both cross-sectional and longitudinal planes of titanium.

The forming limit diagram (FLD) is a useful concept for characterizing the formability of sheet metal. In this work, the formability, fracture mode and strain distribution during forming of Ti6Al4V titanium alloy and Al6061-T6 aluminum alloy sheets has been investigated experimentally using a special process of hydroforming deep drawing assisted by floating disc. The selected sheet material has been photo-girded for strain measurements. The effects of process parameters on FLD have been evaluated and simulated using ABAQUS/Standard. Hill-swift and NADDRG theoretical forming limit diagram models are used to specify fracture initiation in the finite element model (FEM) and it is shown that the Hill-swift model gives a better prediction. The simulated results are in good agreement with the experiment.

Equal channel angular pressing (ECAP) was successfully performed on commercial pure aluminum, aluminum 6061 alloy and commercial pure copper by route BC. Tensile and fatigue (under constant stress) tests shows a significant enhancement in mechanical properties consisting of hardness, yield strength, ultimate tensile strength and endurance limit, but the ductility of the alloys reduced with employing this process. Two fatigue design factors Kl and Kh has been suggested to co-related fatigue data from coarse grained (CG) to ultra-fine grained (UFG) materials.

Flow forming technology is widely used in the production of the axisymmetric industrial parts. The advantage of flow forming process over other manufacturing methods such as press forming is use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical and surface quality of finished parts. In this study, the effects of thickness reduction on the mechanical properties and spinning accuracy are experimentally investigated on 7075-O aluminum tube. A prototype spinning machine has been designed and manufactured. The effects of spinning accuracy, surface roughness, percentage of elongation, yield strength, and the ultimate strength as a function of thickness reduction are experimentally examined. The experimental results show that with increment of thickness reduction, the yield strength, ultimate strength, surface hardness, and crystal refining increase, and on the other hand, it has adverse effect on diameter growth, geometrical accuracy, surface roughness, and percentage elongation of spun tube.

In this study, deformation behavior of commercial pure aluminum in the equal channel angular pressing (ECAP) is analyzed successfully using three dimensional (3D) simulation by finite element methods (FEM). The investigations include the effects of various die channel angles, low-friction and high-friction conditions and the application of the back punch pressure. It is observed that the level of the strain and homogeneity of strain distribution increase with decreasing the die channel angle or increasing the friction coefficient or imposing the back punch pressure in the outlet channel. Also, increasing the magnitude of the strain causes high punch pressure and higher press pressure for processing should be applied.

During the past few decades, ultrafine-grained materials (UFG) have experienced rapid development. Enhanced mechanical and surface properties, such as strength, ductility and erosion-corrosion (E-C) resistance by refining the grain to ultra-fine/nanometer size has been achieved. The equal channel angular pressing (ECAP) is a popular severe plastic deformation (SPD) method to fabricate UFG bulk materials. In this research, the E-C behavior of commercial annealed pure copper subject to four passes of ECAP have been investigated. Hardness measurement of the copper specimen after four passes of ECAP showed an increase of 200% on the hardness value as compared with annealed condition. Simulated seawater was used as an E-C medium. The effect of different E-C parameters such as time, slurry flow velocity, impact angle, and solid particle concentration on ECAP process is studied. The results showed that ECAP enhances the E-C resistance of copper, and this behavior improves with increasing the pass number. Generally, a 30% rise in resistance to E-C was achieved after four ECAP passes as compared to coarse grain copper for the parameters studied in this work. Optical microscopy was used to examine the microstructure and material removal mechanism of the annealed copper. Scanning electron microscopy (SEM) was used to validate the reduction of grain size due to ECAP process. Furthermore, examination of the surface roughness of the copper at different ECAP passes showed that for the same E-C condition the increment of ECAP passes leads to a smoother surface.

Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°. © 2014, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Equal channel forward extrusion (ECFE) is a new method for producing Ultra-Fine Grained (UFG) materials. In this paper, material deformation of pure aluminum in the ECFE process is studied. To this end, firstly, the process is applied to the material and some results such as experimental force and is extracted. Then, the experimental result are used to verify the numerical method which is utilized to evaluate the effect of ECFE die parameters such as main deformation zone height and length to width ratio on the strain and stress distribution, as significant parameters on the die design. To analyze the stress and strain distribution, two planes of the pressed sample, during the ECFE process have been considered. Finally, effect of ECFE parameters on the pressing force as a driving factor has been presented. The results show that effective strain is increased about 300% by increasing length to width ratio about 85.7%. In addition, the lower the length to width ratio applied in ECFE process, the more strain homogeneity is observed.

Equal channel angular pressing (ECAP) is one of the most prominent procedures for achieving ultra-fine grain (UFG) structures among the various severe plastic deformation (SPD) techniques. In this study, the effect of ultrasonic vibration on deformation behavior of commercial pure aluminum in the ECAP process is analyzed successfully using three dimensional (3D) by finite element methods (FEMs). The investigation includes the effects of die geometry, billet length, friction factor, ram speed, ultrasonic amplitude and ultrasonic frequency. Conventional as well as ultrasonic ECAP has been performed on aluminium 1070 alloy and the obtained data were used for validating simulations. It is observed that a 13% reduction in the average force was achieved when ultrasonic vibration with amplitude of 2.5 μm at 20 kHz is applied. Also, further reduction in ECAP forming forces are obtained with increase of vibration amplitude, vibration frequency, friction factor, billet length and die channel angle.

In this paper, a new severe plastic deformation method called equal channel forward extrusion (ECFE) process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength, ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa, 204 MPa and 68 HV as the annealed condition to 269 MPa, 285 MPa and 126 HV after the fourth pass of ECFE process, respectively. In addition, scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1, the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet.

Equal Channel Angular Pressing (ECAP) is currently one of the most popular methods for fabricating Ultra-Fine Grained (UFG) materials. In this work, ECAP process has been performed on commercial pure aluminum up to 8 passes by route A . After verification of FEM work, the influences of four die channel angles, three outer corner angles and pass number up to 8 have been analyzed to investigate strain distribution behavior of ECAPed material. Two methods for quantifying the strain homogeneity namely inhomogeneity index ( C i ) and standard deviation (S.D.) are compared. It is shown that C i is not a good candidate for examining the strain distribution uniformity. Moreover, it is suggested that designing of ECAP die geometry to achieve optimum strain distribution homogeneity is more suitable than the optimum effective strain magnitude. The best strain distribution uniformity in the transverse plane is obtained with Φ =60° and Ψ =15° and for the bulk of the sample, Φ =120° and Ψ =15° or 60°, gives the highest strain dispersal uniformity.