Groove Pressing Research Articles

Finite element modeling and experimental validation of CGP classical and new cross routes for severe plastic deformation of an Al-Mg alloy

In this study, an Al-Mg alloy sheet (AA5052 series) is subjected to a newly modified severe plastic deformation (SPD) process named as constrained groove pressing (CGP). Two different routes of classical and cross are employed and compared for the first time in this research. Each pass of the classical route process is including four subsequent corrugating and straightening stages with a 180-degree rotation between them and imparted an equivalent plastic strain of ∼1.16. Meanwhile, the number of stages for cross route process is eight as well as a 90-degree rotation between the consequent passes and leads to the imposing of a strain ∼2.32. These processes are implemented up to two passes on the examined Al-Mg alloy. As the main objective of the present research, strain and hardness distributions along the main three directions (rolling, transverse, and normal) and from different sections (surface and thickness) during different stages and passes of classical and cross routes are simulated by using 3D non-linear finite element (FE) modeling. ABAQUS/Explicit software is used for this purpose. The effects of classical and cross routes on the strain distributions and homogeneities as well as the hardness profiles during different stages of the CGP process are compared. Also, the simulated results are validated with the experimentally measured hardness data and in accordance some good agreements noticed. Finally, a hardness-tensile strength relationship is established based on the microstructural details and imposed strain contours to predict the tensile strength of processed Al-Mg alloy with the classical and cross routes by the implementation of FE simulation.

Texture variations and mechanical properties of aluminum during severe plastic deformation and friction stir processing with SiC nanoparticles

Annealed 1050-aluminum sheets were severely deformed at the strain magnitude of 2.32 through constrained groove pressing (CGP) process. Texture variations and mechanical properties were investigated during CGP and subsequent friction stir processing (FSP) with different volume fractions of SiC nanoparticles. The results revealed that the predominant texture component in the annealed aluminum was {001}〈100〉 cube texture. After CGP, deformed and shear texture components developed while the cube texture was partially remained. In the specimen undergone FSP without nanoparticles, {001}〈110〉 rotated cube and nearly {001}〈110〉 shear texture component C were mainly pronounced, which was indicative of shear deformation of material in the stir zone. Orientation distribution function analysis from the stir zone demonstrated variations in the texture development with the incorporation of SiC nanoparticles. An increase in the fraction of nanoparticles changed the grain orientation in such a way that the {001}〈110〉 shear texture component C gradually developed from the rotated cube texture. However, the overall texture intensity became weaker by increasing the fraction of SiC nanoparticles due to the activation of particle stimulated nucleation mechanism forming randomly oriented grains. The incorporation of SiC nanoparticles in the stir zone also enhanced the yield strength, Young's modulus, and hardness of the stir zone without considerable reduction in the elongation. In such situation, Orowan strengthening was suggested as a dominant mechanism involved.

Structure and Mechanical Properties of Aluminum 1560 Alloy after Severe Plastic Deformation by Groove Pressing

The paper analyzes the structure and mechanical properties of sheet-rolled Al 1560 alloy after four cycles of groove pressing. The analysis shows that under quasi-static uniaxial tension at a strain rate of 1 s-1, the offset yield strength of the groove-pressed alloy and its ultimate strength are respectively 1.4 and 1.5 times higher than their values in the as-received state. The ultimate tensile strain of the alloy after pressing is 17% against 21% in the as-received state, and its microhardness is 2.7 times higher. According to an electron backscatter diffraction analysis, the groove-pressed alloy has a bimodal structure composed of elongated coarse grains and agglomerates of equiaxed grains of micron and submicron sizes. When pressed, the alloy increases the density of its grain boundaries with a misorientation angle of less than 15° and changes its texture from rolling to upsetting whose volume during pressing grows. Part of the grain orientations in both states corresponds to recrystallization. The research data suggest that groove pressing provides grain structure refinement via plastic distortion in Al 15 60 alloy and a considerable increase in its strength properties.

Interface sheet-constrained groove pressing as a modified severe plastic deformation process

ABSTRACTIn this paper, a new severe plastic deformation (SPD) process entitled interface sheet-constrained groove pressing (ISCGP) as a new variant of conventional CGP has been developed for producing ultrafine-grained metallic materials. In this process, repetitive shear deformation is imposed into the sheet material by utilising symmetrically grooved die along with two interface sheet on both sides. To study the applicability, mild steel sheets were processed by both ISCGP and CGP processes, and mechanical and microstructural properties of the processed samples were investigated. The results show a considerable improvement in mechanical properties including hardness, yield strength, and ultimate tensile strength, though the ductility sacrifice was reduced. Comparing ISCGP and conventional CGP revealed interesting results, which are shown that ISCGP can result in better surface quality and ductility.

Analysis of constrained groove pressing and constrained groove pressing-cross route process on AA5052 sheet for automotive body structure applications

In this paper, a hybrid experimental-numerical approach was developed to analyze the constrained groove pressing and constrained groove pressing–cross route process on AA5052 sheets which are comprehensively used to produce body in white and closure panels and beams of the automotive. The microstructure and mechanical properties were evaluated using scanning electron microscopy, tensile tests, and microhardness measurements. Then, the developed procedure was used to predict the mechanical properties of the sheets fabricated by constrained groove pressing process. This enabled the evaluation of the effects of the groove angle, width, and height of the die on strength and hardness of the processed sheets. To complete the conceptual design of the grooved dies, the Taguchi method was used to optimize the die design. The obtained results show that the inhomogeneity factor in the sheets processed by constrained groove pressing–cross route is less than those processed by constrained groove pressing. The analysis indicates that the developed procedure would result in an acceptable prediction of the material behavior of the processed sheets. The procedure could save a great deal of time and is economical in the matter of design. Finally, the procedure in conjunction with Taguchi method would lead to an optimum die design to enrich the processed sheets.

Experimental Investigation of Mechanical Behavior of a Polyamide before and after Constrained Groove Pressing Process

In this paper an experimental investigation of mechanical behavior of a thermoplastic polymer (polyamide PA 66) processed by constrained groove pressing (CGP) using several passes is presented. To this end, corrugating and straightening tools are designed and manufactured. The effects of the number of passes and the hold time on the mechanical behavior of the polyamide have been highlighted. The obtained results show that the material properties and the microstructure are significantly altered under CGP process. It has been found that the microhardness and the tensile properties have been progressed accordingly to the number of cycles, especially when the samples are processed using a hold time of five minutes. Hence, it can be concluded that this latter plays a very important role on the reorientation and stabilization of the microstructure when the processed material is a polymer.

Mechanistic insight into the role of severe plastic deformation and post-deformation annealing in fracture behavior of Al-Mn-Si alloy

Dual-straining by constrained groove pressing (CGP) (εeff = 2.32) and cold rolling (CR) (εr = 0.47, 0.8, and 12.7) under different routes (direct cold rolling (DCR) and cross cold rolling (CCR)) performed on Al-Mn-Si sheets. In the following, thermal treatments (Ta = 150, 250, and 350 °C) conducted as supplementary processing on deformed specimens. Microstructural investigations and mechanical examinations carried out to study straining path effects. It was revealed that further straining through DCR route was more influential in ultimate grain refinement and strength enhancement. Despite DCR, CCR displayed prominent role in elongation deterioration. By post-deformation annealing of dual-strained specimen at Ta = 350 °C through DCR, ductility enhancement more than 1000% was obtained. Fractography implicated fracture-angles ranged θf = 44.5–66° which had inverse correlation with contribution of post uniform deformation (PUD) in tensile tests. Diverse fracture morphologies (fibrous, slip, rupture, and shear) examined by SEM while area contribution of each fluctuated by εr and Ta. Increase in rupture fraction observed in more brittle fracture. Characterization of size, morphology and chemical composition of second-phase precipitates proved that they were fragmented, nucleated from matrix under dynamic precipitation and also enriched in alloying elements; however, just those had certain minimum size could find chance to contribute in dimple formation.

Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum

The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrained groove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at room and cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grain structure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattered diffraction. The annealed sample contained a large number of “recrystallized” grains and relatively large fraction (78%) of high-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grains with interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. The GOS map of the severely deformed specimen manifested the formation of 43% “distorted” and 51% “substructured” grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBs from 20 to 60%. Also, it gave rise to the formation of “recrystallized” grains with the average size of 13 μm, which were coarser than the grains predicted by Zener–Hollomon parameter. This was attributed to the occurrence of appreciable grain growth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain size was decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientation was the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensile tests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strength of the severely deformed aluminum.

On the role of applying groove pressing technique before friction stir processing of copper: microstructure and mechanical evaluation

The effect of prior constrained groove pressing on friction stir processing (FSP) of pure copper was investigated. The results illustrate the development of high strain and strength of FSP samples along with an increased strength base metal as a result of applying for a prior constrained groove pressing (CGP) pass. The influences of further FSP passes on the microstructures, and mechanical properties were also shown. The microstructural evaluation of the specimens indicated up to 10 times grain size reduction in FSP specimens as well as equiaxed microstructural morphology. Mechanical properties of the specimens were carried out through tensile and microhardness tests. It was demonstrated that the FSP could improve the strength and ductility of the specimens simultaneously through improved mechanical properties of the base metal resulting from prior CGP. The performed calculations show that values of dislocation density of the CGPed specimens experienced significant change after applying for FSP passes.

Deep Drawing of constrained groove pressed EDD steel sheets

Constrained groove pressing (CGP) is a severe plastic deformation process for producing ultra-fine grained sheet metal without any change in the initial dimensions. CGP works on the principle of repetitive shear deformation of the material by alternate pressing by using asymmetrically grooved die and flat die constrained tightly by boundaries of the die. In this study, CGP, up to two passes has been performed on Extra deep drawing (EDD) steel specimens. To study the formability, the CGPed steel specimens have been deep drawn using a typical deep drawing setup and the limiting draw ratio (LDR) has been calculated. This LDR of CGPed material has been compared to the LDR of cups drawn using as-received EDD steel blanks. The formability of the CGPed material is almost the same as that of the as-received material. Apart from this, micro-hardness study of the cups has also been done on a similar comparative basis. These investigations show a slight improvement in the hardness values. It is found that by doing two passes of CGP on EDD steel, stronger cups can be produced without sacrificing much of the formability.

Influence of Constrained Groove Pressing Passes and Annealing Characteristics on the Mechanical Properties of 6061 Aluminum Alloy

An ultra-fine grain (UFG) material exhibits a high strength without the degradation of toughness. Constrained groove pressing (CGP) is one of the severe plastic deformation techniques, which will be used to produce ultra-fine grained microstructures. The silicon series alloy of aluminum 6061 (AA6061), having larger grain size, is subjected to severe plastic deformation using CGP technique. The ultimate tensile strength and hardness of severely plastically deformed specimens were determined. In addition, thermal stability of the severely deformed microstructure was evaluated by exposing to temperature of 125 °C at exposure duration of 25, 50, 75, 100 and 125 minutes. The CGPed A6061 samples exhibited superior mechanical properties owing to its refined UFG microstructure. Results of annealed samples showed that the tensile strength and micro-hardness of CGPed was still higher than the unprocessed samples, demonstrating the reasonable thermal stability of CGPed AA 6061 samples. It is presumably due to the existence of extensive trident grain boundaries and obstruction of grain boundary movement due to pinning effect caused by dispersed precipitate phases in UFG.

Finite element analysis of the deformation behaviour of pure aluminium in repetitive corrugation-straightening and constrained groove pressing

Repetitive corrugation-straightening (RCS) and constrained groove pressing (CGP) are two promising severe plastic deformation techniques for sheet metallic materials. There are differences in amount of imposed plastic strain, hence, it is important to compare the deformation mode in these two techniques. In the present paper, the effect of RCS and CGP on the deformation behaviour of pure aluminium is studied. The effective parameters are analysed using finite element analysis (FEA) for one pass of deformation. The computer simulations are carried using DEFORM-3D and to verify the FEA results, a comparison with previous literatures is made. It is observed that filling ratio of the die is higher for CGP. Additionally, the deformed work-piece endured more plastic strain in CGP and the effective strain is more homogenously distributed in this technique.

Finite element analysis of the deformation behaviour of pure aluminium in repetitive corrugation-straightening and constrained groove pressing

Repetitive corrugation-straightening (RCS) and constrained groove pressing (CGP) are two promising severe plastic deformation techniques for sheet metallic materials. There are differences in amount of imposed plastic strain, hence, it is important to compare the deformation mode in these two techniques. In the present paper, the effect of RCS and CGP on the deformation behaviour of pure aluminium is studied. The effective parameters are analysed using finite element analysis (FEA) for one pass of deformation. The computer simulations are carried using DEFORM-3D and to verify the FEA results, a comparison with previous literatures is made. It is observed that filling ratio of the die is higher for CGP. Additionally, the deformed work-piece endured more plastic strain in CGP and the effective strain is more homogenously distributed in this technique.

Microstructures evolution and mechanical properties of 5052 aluminium alloy processed by constrained groove pressing

Commercial 5052 aluminium alloy sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP) at room temperature. The impact of repeated CGP, upon the microstructure refinement was investigated by polarised optical microscope as well as transmission electron microscope. Changes in mechanical properties, measured by tensile test and hardness test, were related to the evolution of microstructures. Moreover, the microhardness, measured on the polished cross-section of each as-pressed sheet, was plotted to provide a pictorial depiction of the homogeneity. The results show that the mechanical fragmentation dominates at grain refinement and a submicron grain size of about 300 nm was achieved in 5052 aluminium alloy sheets by imposing severe plastic strains of 4.64 utilising the CGP technique. The average microhardness increase dramatically after one pass and then slightly increases with increasing passes, but the homogeneous distribution of microhardness decreases after one pass and then recovers in subsequent passes result in the corresponding uniform distribution of microstructure. In addition, the ultimate tensile strength clearly increases with increasing passes and the elongation decreases after one pass and then remains reasonably constant with further passes.

Microstructures evolution and mechanical properties of 5052 aluminium alloy processed by constrained groove pressing

Commercial 5052 aluminium alloy sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP) at room temperature. The impact of repeated CGP, upon the microstructure refinement was investigated by polarised optical microscope as well as transmission electron microscope. Changes in mechanical properties, measured by tensile test and hardness test, were related to the evolution of microstructures. Moreover, the microhardness, measured on the polished cross-section of each as-pressed sheet, was plotted to provide a pictorial depiction of the homogeneity. The results show that the mechanical fragmentation dominates at grain refinement and a submicron grain size of about 300 nm was achieved in 5052 aluminium alloy sheets by imposing severe plastic strains of 4.64 utilising the CGP technique. The average microhardness increase dramatically after one pass and then slightly increases with increasing passes, but the homogeneous distribution of microhardness decreases after one pass and then recovers in subsequent passes result in the corresponding uniform distribution of microstructure. In addition, the ultimate tensile strength clearly increases with increasing passes and the elongation decreases after one pass and then remains reasonably constant with further passes.

Electrical annealing of severely deformed copper: microstructure and hardness

Commercial pure copper sheets were severely deformed after primary annealing to a strain magnitude of 2.32 through constrained groove pressing. After induction of an electrical current, the sheets were heated for 0.5, 1, 2, or 3 s up to maximum temperatures of 150, 200, 250, or 300°C. To compare the annealing process in the current-carrying system with that in the current-free system, four other samples were heated to 300°C at holding times of 60, 90, 120, or 150 s in a salt bath. The microstructural evolution and hardness values of the samples were then investigated. The results generally indicated that induction of an electrical current could accelerate the recrystallization process by decreasing the thermodynamic barriers for nucleation. In other words, the current effect, in addition to the thermal effect, enhanced the diffusion rate and dislocation climb velocity. During the primary stages of recrystallization, the grown nuclei of electrically annealed samples showed greater numbers and a more homogeneous distribution than those of the samples annealed in the salt bath. In the fully recrystallized condition, the grain size of electrically annealed samples was smaller than that of conventionally annealed samples. The hardness values and metallographic images obtained indicate that, unlike the conventional annealing process, which promotes restoration phenomena with increasing heating time, the electrical annealing process does not necessarily promote these phenomena. This difference is hypothesized to stem from conflicts between thermal and athermal effects during recrystallization.

Rapid annealing of severely deformed low carbon steel in subcritical temperature range

A low-carbon steel sheet containing 0.05 C, 0.203 Mn, and 0.0229 Si (all in wt%) was rapidly annealed in a temperature range of 300 °C to 600 °C after severe plastic deformation by using constrained groove pressing (CGP) technique. Microstructure evolution was investigated by scanning electron and optical microscopes. Mechanical properties were evaluated by hardness measurements and shear punch test. The results showed a thermal stability up to 400 °C where recrystallization did not occur in the specimens even after 7200 s. This thermal stability is in agreement with previously reported results of conventional annealing of the same steel after CGP. However, annealing at 500 °C and 600 °C led to recrystallization which started after holding times of 600 s and 20 s, respectively. Longer holding times resulted to grain growth and deterioration of strength and hardness, but the final strength and hardness were still higher than those of conventionally annealed specimens. The reason has been attributed to no abnormal grain growth in the present study, in contrast to that occurs after conventional annealing of CGPed low carbon steel. The kinetics of recrystallization at 600 °C was studied using the celebrated Johnson-Mehl-Avrami-Kolmogorov (JMAK) model; the results showed a bi-linear JMAK plot indicating two different stages of recrystallization rate before and after 70% recrystallization.

Microstructure, hardness homogeneity, and tensile properties of 1050 aluminum processed by constrained groove pressing

1050 commercial purity aluminum was subjected to severe plastic deformation through constrained groove pressing (CGP) at room temperature. Transmission electron microscope observations showed that after four CGP passes the majority of microstructure is composed of elongated grains/subgrains whose width/length average sizes are 506/1440 nm. This ultrafine-grained microstructure leads to a significant increase in yield strength of starting material from 93 to 182 MPa. At the same time, after four passes of CGP the material still displays a considerable ductility of 19%. Microhardness profiles reveal that average microhardness value in sample increases monotonically with increased straining during CGP. However, the degree of deformation homogeneity in samples remains almost unchanged at higher number passes. The latter was also confirmed by non-uniform distribution of imposed plastic strain in samples predicted by finite-element analysis.

The Effect of a Severe Plastic Deformation by Groove Pressing on the Grain Structure of the Al-Mg Alloy

In this article, the effect of a severe plastic deformation (SPD) achieved by groove pressing (GP) on the grain structure and mechanical properties of a rolled sheet Al-Mg alloy was investigated. The study of the microstructure of the samples before and after processing was carried out by means of electron backscattered diffraction (EBSD). The mechanical properties of the samples were experimentally studied under uniaxial tension in quasi-static conditions, and microhardness testing was implemented. It was found that the conventional yield strength and ultimate tensile strength increase by the factor of 1.4 and 1.5, respectively; and the microhardness increases by approximately 2.7 times after four machining sequences of the rolled sheet alloy. A bimodal grain structure, consisting of two grain types with particular features, is formed in the samples after four machining sequences of GP.

Groove pressing and its research progress

Groove pressing and its research progress