Constrained Groove Pressing Research Articles

A profound study of damage behavior for Al 2024-T3 alloy worksheet produced by constrained groove pressing in the superior practical condition

Constrained groove pressing (CGP) process is one of the most efficient and novel methods of severe plastic deformation to manufacture ultra-fine sheet metal. The present research work is related to the study of CGP process of 2024-T3 Aluminum alloy sheet. The empirical and numerical simulation of CGPed- specimens have been examined at both room and elevated temperatures. In order to simulate the constrained groove pressing process in Abaqus software, the Johnson–Cook material model has been employed. The geometrical variables of the CGP process include the teeth number, teeth angle, and sheet thickness, and the criterion for the superiority of the numerical test is the maximum reduction of two equivalent strain and equivalent force factors, simultaneously. To determine the weight’s coefficients of the target factors and select the superior test, the Shannon’s Entropy and Simple Additive Weighting (SAW) methods have been used, respectively. After validating the numerical findings, the variation of damage parameter, stress triaxiality and the equivalent plastic strain distribution in the superior practical condition have been evaluated in detail. Based on the Entropy-SAW hybrid technique, the weight’s coefficients of equivalent strain and equivalent force target factors were computed to, in turn, 0.38 and 0.62. Also, the results revealed that the CGP process could not be performed at room temperature based on high damage evolution. But, at elevated temperature, the damage parameter (D) doesn't exceed 0.26. Also, the maximum stress triaxiality and equivalent plastic strain (PEEQ) at this process temperature reached to 0.5 and 0.1, respectively.

Friction stir welding of constrained groove pressed Al1050 using Al2O3 nanoparticles

In this investigation, two passes Constrained Groove Pressed (CGPed) Al1050 sheets went through Friction Stir Welding (FSW) by adding nano-sized Al2O3 particles. Then, the microstructure and mechanical properties of the welded joints, undergone various pass numbers and rotational to traverse speed (ω/ν) ratios, were presented. Findings showed all joints were fractured from the SZ, although HAZ softening happened due to grain growth in this region. The presence of the Al2O3 particles in the stir zone led to a fine and equiaxed grain structure, resulting from continuous dynamic recrystallization (CDRX) during the high-temperature welding process. This grain refinement contributed to an improvement in the mechanical properties of the joints, such as strength and microhardness. Employing two different ω/ν ratios resulted in a variety of thermal cycles during the welding procedure such that the peak temperature in the ω/ν of 70 and 25 r/mm reached ∼423 °C and ∼285 °C, respectively. Microstructure studies via optical observation and EBSD analysis illustrated that employing a higher ω/ν ratio and weld pass number resulted in more uniform particle distribution in the stir zone thanks to facilitating materials flow and incorporation during FSW. As a result, the three passes FSWed sample at the higher ω/ν ratio of 70 r/mm showed the most homogeneous particle distribution and finest grain structure in the SZ. This microstructure evolution was in reliable agreement with the mechanical performance of the joints. The three passes FSWed sample at the higher ω/ν ratio of 70 r/mm demonstrated the highest weld strength, microhardness, and %elongation compared to other FSWed joints. This sample showed an ultimate tensile strength (UTS) of ∼97 MPa and a %elongation of ∼16%, and its mean microhardness value had a ∼3.5% increase compared to the CGPed base metal. Conversely, the one pass FSWed sample at the lower ω/ν ratio of 25 r/mm represented the weakest mechanical properties due to cavities, defects, and agglomerated Al2O3 nanoparticles. The presence of nanoparticles was a decisive factor in microstructural evolution during the welding, thereby increasing the mechanical quality of the joints dependent upon their uniform dispersion, obtained by increasing the pass number and ω/ν ratio.

Constrained groove uniform pressing process for achieving homogeneously improved properties in copper

Constrained groove pressing (CGP) is a popular method to produce an ultrafine-grained microstructure and thus enhanced mechanical properties in the metal sheet. CGP is a severe plastic deformation technique that simultaneously presses the metal sheet with flat and grooved dies to subject it to large shear strain without changing the dimensions. The inherent inhomogeneity of the processed sheet may be a drawback of the CGP process. According to published research, this is caused by the sharp edges of the grooved dies responsible for additional bending strain along with shear strain. Moreover, even if the grooves are made circular, it can impart constant bending strain, but the shear strain varies. In this research, a new die has been designed to impart constant combined bending and shear strain in the metal sheet using constrained groove uniform pressing. Hence, the process is changed as the number of presses required for 1 pass are changed and named constrained groove unform pressing. C101 was used as the material for the new process. Properties of the copper sheet observed to be improved homogeneously as it was processed through the new die and process. The uniformity of the imposed strain was verified by theoretical, experimental, and simulation results.

Optimal Constrained Groove Pressing Process Parameters Applying Modified Taguchi Technique and Multi-Objective Optimization

Most engineering problems are complicated, and developing mathematical models for such problems requires understanding the phenomena through experiments. It is well known that as processing parameters with assigned levels increase, so does the number of experiments. By minimizing the number of experiments, Taguchi’s method of experimental design will help to furnish the idea of full factorial experimental design. Taguchi’s method is more appropriate for single-objective optimization problems and needs modifications while dealing with multi-objective optimization problems. Aluminum alloys are in great demand in today’s automotive and aerospace sectors due to their low density, good corrosion resistance, and excellent machinability. The material is subjected to a constrained groove pressing (CGP) process to obtain microstructural grain refinement with enhanced mechanical behavior. This paper considers AA6061 material having major alloys such as silicon and magnesium. For this work, 3 CGP process parameters (viz., displacement rate, plate thickness and number of passes) are assigned 3 levels to each parameter, acquired the test data, viz., grain size (gs), micro hardness (hs), and tensile strength (ult) based on L9 orthogonal array of Taguchi. Using a modified version of Taguchi’s methodology, it is possible to estimate the range of grain size (gs), micro hardness (hs), and tensile strength (σult) for effective combinations of the CGP processing parameters and validate the results with existing test data. A more dependable and simpler multi-objective optimization procedure is used to choose the optimal CGP processing parameters.

Near Net Shape Manufacturing of Sheets from Al-Cu-Li-Mg-Sc-Zr Alloy.

Thin twin-roll cast strips from a model Al-Cu-Mg-Li-Zr alloy with a small addition of Sc were prepared. A combination of a fast solidification rate and a favorable effect of Sc microalloying refines the grain size and the size of primary phase particles and reduces eutectic cell dimensions to 10-15 μm. Long-term homogenization annealings used in conventionally cast materials lasting several tens of hours followed by a necessary dimension reduction through rolling/extruding could be substituted by energy and material-saving procedure. It consists of two-step short annealings at 300 °C/30 min and 450 °C/30 min, followed by the refinement and hardening of the structure using constrained groove pressing. A dense dispersion of 10-20 nm spherical Al3(Sc,Zr) precipitates intensively forms during this treatment and effectively stabilizes the structure and inhibits the grain growth during subsequent solution treatment at 530 °C/30 min. Small (3%) pre-straining after quenching assures more uniform precipitation of strengthening Al2Cu (θ'), Al2CuMg (S'), and Al2CuLi (T1) particles during subsequent age-hardening annealing at 180 °C/14 h. The material does not contain a directional and anisotropic structure unavoidable in rolled or extruded sheets. The proposed procedure thus represents a model near net shape processing strategy for manufacturing lightweight high-strength sheets for cryogenic applications in aeronautics.

Constrained Constant Radius Pressing (CCRP) process to improve mechanical properties and microstructural homogeneity of pure copper sheet

Constrained groove pressing (CGP) is a well-known severe plastic deformation (SPD) process used to improve the mechanical properties of metallic sheets by forming the ultrafine grain (UFG) structure. The conventional CGP process employs 45° grooved dies to impart good amount of plastic strain on the specimen without altering the specimen's initial dimensions. The literature indicates that conventional CGP-processed sheets have inherent strain inhomogeneity. In the present investigation, an effort was made to minimize the inherent strain inhomogeneity by modifying conventional CGP dies into symmetric constrained constant radius pressing (CCRP) dies. Three distinct CCRP dies with varying radius of curvature and die parameters were designed to attain the optimal combination of mechanical properties. It was found that metal sheets processed by new modified dies (CCRP) exhibit improved ductility and significantly enhanced toughness, in contrast to the sheets processed by conventional CGP dies. The improvement in mechanical properties could be attributed primarily to homogeneous grain refinement. In addition, the finite element analysis (FEA) was used to simulate the influence of different die designs on the strain distribution across the sheet, and it showed that lower die angle of CCRP lead to more homogeneous distribution of strain across the arc of the CCRP die.

Mechanical and microstructural characterization of Nimonic 263 superalloy after constrained groove pressing at elevated temperatures

Nimonic 263 superalloy is primarily being used in gas turbines, high-pressure pipelines, steam heaters, etc. due to its capability to withstand high temperatures and pressure for a longer duration. In this work, an experimental investigation on Nimonic 263 alloy has been carried out to improve its mechanical and microstructural properties using constrained groove pressing (CGP) at various temperatures. CGPed specimens have been characterized through mechanical tests (tensile test and hardness test) and microstructural studies (XRD, SEM fractography, and optical microscope). The results demonstrated that the CGP process had a significant impact on the alloy's properties. Compared to the as-received material, the CGPed specimens exhibited substantial improvements in yield strength (YS), ultimate tensile strength (UTS), and micro hardness, with average values of 234.58%, 43.79%, and 110.31%, respectively. The average grain size gets reduced due to CGP from 220.70 μm for the as-received material to 106.02 μm, 117.09 μm and 94.01 μm for CGP at room temperature, 250o C, and 450o C, respectively. An increase in the peak intensity is observed in the XRD after the CGP process due to a decrease in crystal size and an improvement in dislocation density with an average value of 31.68%. Fractography studies have revealed a mixed-mode (ductile and brittle) failure for the CGPed specimens compared to the ductile failure mode in the as-received material. Using Abaqus 6.14 software, the finite element analysis of the CGP process has been performed and the results have been found in good agreement with the analytical results. Thus, the CGP process can effectively improve the mechanical and microstructural properties of Nimonic 263 alloy for high-temperature applications.

Superior combined strength and elongation by conducting elevated temperature constrained groove pressing on Al–Mg–Mn sheets

Al 5083 alloy has widely been employed in marine and offshore engineering as well as production of various types of superplastically formed parts in aerospace and automotive industries. The constrained groove pressing (CGP) is also one of important sheet severe plastic deformation (SPD) technique. In this study, The CGP process has been performed on Al 5083 sheets at an elevated temperature and up to three cycles. Complementary experiments, namely metallography, precipitation evolution, hardness and tensile tests as well as fractography were conducted for various deformed and undeformed sheets. The 1-passed workpiece represented the minimum average grain size (AGS) 8 μm due to huge strain induction. By computing the inhomogeneity factor (IF), it was also found that the 2-passed sample was the most inhomogeneous worksheet with an IF of 6.3. By performing three CGP cycles, superior elongation of 56.2% combined with UTS of 309 MPa were achieved for the 3-passed sample, making this workpiece very suitable for conducting any subsequent metal forming process. This was mainly due to the precipitation evolutions of Al6(Fe,Mn) and Al3Mg2 particles. Moreover, fractography of various specimens showed that by performing greater number of CGP cycles, the fracture mechanisms changed to a ductile mode due to creation of tiny and deep dimples.

Strength enhancement and uniform strain distribution through cross route-constrained groove pressing

Constrained groove pressing (CGP) is one of the severe plastic deformation techniques for sheet metals to impose large plastic strain and produce ultrafine-grained (UFG) structures without any change in dimensions. Cross route-constrained groove pressing (Cross-CGP), an advanced version of the conventional CGP process, involves two CGP cycles with an equivalent strain of 2.32 per cycle where the square sample is rotated by 90° after performing every cycle of CGP. The strain path in the sheet during conventional CGP and cross-CGP significantly affects the homogenization of mechanical properties. Sheets of low carbon steel are processed through conventional-CGP and cross-CGP routes. The ability to sustain the maximum strain has been increased in the cross-CGP process due to uniform strain distribution. The tensile strength and hardness in the sheet processed through cross-CGP are higher than that of conventional CGP, especially at higher pass numbers. Tensile behavior and hardness in two different orientations (parallel and perpendicular to the groove direction) have been found to be almost the same in the cross-CGP processed sheet.

Microstructure evolution, mechanical properties, and strengthening mechanisms of 6061 aluminum alloy processed via corrugated constrained groove pressing

In this study, a corrugated constrained groove pressing (CCGP) technology based on a semicircle groove was proposed, improving the uniformity of strain accumulation in deformed metal sheets through staggered groove pressing. First, 6061-O aluminum alloy was processed at room temperature via conventional CCGP (Conv-CCGP) and 90° cross CCGP (Cross-CCGP). The effects of strain route and deformation pass on the microstructure evolution of the CCGPed alloy were investigated and correlated with mechanical properties. Changes in the mechanical properties of the CCGPed alloy at room temperature measured via tensile in different directions and hardness tests were studied. Results showed that the strength and hardness of the CCGPed sheet in both routes were considerably improved, but ductility was decreased. Cross-CCGP can effectively alleviate the anisotropy of the deformed sheet and achieve optimal strength in roll direction (RD) and transverse direction (TD) at two passes. Yield strength (YS) and ultimate tensile strength (UTS) along RD were increased by 190.2% and 15.5% relative to the initial alloy, reaching 119 MPa and 134 MPa, respectively. Along TD, YS and UTS were increased by 255.0% and 36.0%, reaching 142 MPa and 151 MPa, respectively. Characterization techniques, including electron backscatter diffraction and high-resolution transmission electron microscopy, were used to establish comprehensive models of dynamic recovery-based substructure evolution and dynamic recrystallization-dominated grain refinement. Meanwhile, the integrated microstructural changes and theoretical calculations identified dislocation strengthening and local grain refinement as the major contributors to the strengthening of the CCGPed alloy. In addition, tensile fracture surface analysis showed that the CCGPed alloy still underwent plastic fracture, but the fracture mode shifted from tension fracture into shear fracture.

Re-examination and comparison of activation volume, strain rate sensitivity, and dislocation density for coarse grain and CGP-processed UFG materials

The frequently used metallurgical parameters such as activation volume, internal stress, strain rate sensitivity, and dislocation density are identified in ultrafine-grained (UFG) materials through erudite analytical relations. It is difficult to analyze such parameters optically since the material consists of highly distorted and inhomogeneous microstructure due to the large strain imposed during the constrained groove pressing (CGP) process. Hence, transient tests like stress relaxation tests are advantageous over the optical to use. Apart from the identification of parameters in low-carbon steel materials using uniaxial loading and stress relaxation tests, the relationship between the parameters is nobly investigated in as-received and UFG structure samples produced through the CGP process. In the relationship, the exponential-power law constitutive to describe the accurate stress–strain curves, identification of mobile and forest dislocation density during strain hardening, and exponential variation between grain size and activation volume are proposed. The replenishment or exhaustion of mobile and forest dislocation density significantly affects the metallurgical parameters during uniaxial tensile loading followed by stress relaxation testing. In this experimental and analytical work, the CGP process produces a UFG material that has lower activation volume and higher stress drop, mobile dislocation density, forest dislocations density, strain rate sensitivity, and internal stress.

Utilisation of fuzzy logic and genetic algorithm to seek optimal corrugated die design for CGP of AZ31 magnesium alloy

ABSTRACT Magnesium alloys are the first choice among other lightweight structural metals like aluminium, titanium and beryllium due to low density and excellent corrosion resistance. However, low slip and cold plastic processing ability limits its applications. Constrained groove pressing (CGP), one among the SPD techniques, is well suited for improving the material properties. Corrugated dies are designed to investigate the deformation behaviour of AZ31 Mg alloy samples. To minimise the number of numerical simulations, Taguchi’s L9 orthogonal array is selected for the grooved die dimensions (viz. groove angle, groove width and coefficient of friction). Elasto-plastic finite element analysis is performed by implementing a multi-criterion-based genetic algorithm optimisation tool for obtaining the optimal die geometry. Reduction in total deformation, increase in the equivalent stress and elastic strain of AZ31 sheet were possible with 50° groove angle, 3 mm groove width and 0.22 friction coefficient. Mamdani-based fuzzy logic soft computing tool is implemented for the model to examine the deformation behaviour of AZ31 Mg alloy. 7.86 % deviation is observed in the fuzzy logic model predictions in comparison with simulation results. The suggested die design is well suitable for multiple CGP passes, to improve the grain refinement in the processed sheet.

Directional fretting wear behaviour of constrained groove pressed aluminium sheet

Wear behavior of the constrained groove pressed (CGP) aluminium (Al) sheet was examined along both the longitudinal as well as transverse direction using fretting wear tester. The results unequivocally showed a significant diminution (up to 1.2 times for one pass) in the coefficient of friction (COF) which leads to significant improvement in the wear resistance after each pass of CGP when compared to the as-received (AR) sample. Subsequently, wear rate in the CGP processed sample was found to be lower along the transverse direction (∼ 0.38 ± 0.08 ×102 µm3/N.mm) compared to that in the longitudinal direction (∼ 0.87 ± 0.12 ×102 µm3/N.mm) for one pass sample. Along longitudinal direction the major wear mechanism is discerned to be severe abrasion followed by crater formation in the samples with lower strain (i.e. 1 pass), however, it is delamination followed by dense tribolayer formation in the highly strained sample along transverse direction. Increasing fraction of oxygen content in energy dispersive spectroscopy result support the formation of dense tribolayer along transverse direction which attribute to formation of protective layer in the wear scar. The substantial decrement in the wear volume and hence wear rate after severe deformation is credited to the significant strain imposed in the sample, which leads to significant hardness up to ∼ 1.5 times for 3 pass CGP (44.5 VHN) due to the grain refinement from AR to 3 pass CGP i.e., ∼ 21.64 µm to ∼ 5.60 µm. Therefore, effect of grain refinement on the mechanical as well as wear properties with CGP on Al substrate has also been established.

Inclusive anisotropy and texture analyses of AZ91 Mg sheets subjected to various passes of elevated-temperature constrained groove pressing

Constrained groove pressing (CGP) is a kind of sheet severe plastic deformation method suitable for enhancing the strengths of light alloys for various applications such as aerospace and automotive industries. In this research, the annealed AZ91 Mg alloy sheets were subjected to three CGP cycles at 300°C. Subsequently, optical microscopy, scanning electron microscopy, x-ray diffraction, and tensile tests for various directions were performed. Initially, there was a basal texture with a maximum intensity of 3.4 multiple random distribution and several β-Mg17Al12 particles as the second phase in the annealed sheet. As an important achievement of employing the CGP operation, the 1-passed sample represented a superior elongation of 35.7%, maximum yield strength of 141.0 MPa, and maximum ultimate tensile strength of 231.0 MPa in the rolling direction. These were mainly due to, the grain refinement, enhancing the fiber texture in the transverse direction, and controlling the basal texture. However, the experimental results revealed that the basal texture during the second and third passes of the operation could not be controlled. The main preferred orientation was changed from [Formula: see text] fiber for the annealed sheet to [Formula: see text] fiber for the CGPed sheets. It is also interesting to note that based on an anisotropy analysis, the 1-passed sample was the most isotropic worksheet, making this specimen a suitable blank for secondary metal forming processes, in comparison with the other CGPed samples. Fractography also indicated that the fracture mechanism varied among ductile, brittle, and mixed modes for workpieces subjected to different passes of the process.

Effects of constrained groove pressing and temperature-assisted ultrasonic shot peening on microstructure and mechanical properties of a two-phase Mg–Li alloy

Two passes of constrained groove pressing (CGP) were conducted on a two-phase Mg–Li alloy followed by temperature-assisted ultrasonic shot peening (TA-USP) with different peening durations and temperatures. The effects of TA-USP and CGP on microstructural evolution and mechanical properties were investigated in details. Surface gradient microstructure including nanocrystalline and partial amorphization is introduced by TA-USP. Grain refinement is more significant with longer durations and lower temperatures. Pretreatment by CGP before TA-USP introduces fine and homogeneous microstructure in the alloy due to severe plastic deformation. The average grain sizes of α-Mg and β-Li are refined from the as-annealed 31.6 μm and 12.9 μm to 2.5 μm and 2.2 μm, respectively. The depth of USP-affected region increases with the increase of peening duration and temperature, and a depth of about 300 μm is achieved by direct TA-USP at room temperature with 400 s. The microstructure gradient is reduced at elevated temperatures. The hardness and strength increase while the ductility decreases with the increase of peening duration. The decrease in hardness with the increase of peening temperature is more significant than peening duration. Compared with direct TA-USP, pretreatment by CGP before TA-USP can obviously enhance the surface strengthening. When processed by TA-USP at 200 °C with 100 s, the tensile strength and yield strength increase from 141.9 MPa and 106.2 MPa to 158.3 MPa and 134.7 MPa, respectively. The elongation to failure decreases from 29.1% to an acceptable value of about 16.1%.

Developing methods of constrained groove pressing technique: A review

Among various severe plastic deformation (SPD) techniques, constrained groove pressing (CGP) has arisen as a famous technique for fabricating ultrafine-grained sheet metals and alloys in recent times. The severe strain is applied to improve the mechanical performance and properties. However, inhomogeneous grain refinement, lower formability, surface unevenness, and microcracks are the common limitations of conventional CGP-processed samples. Therefore, this review inspects the latest progress through modifications of the CGP process and compares the process efficacy with the conventional process. Advanced CGP processing techniques, such as modification of die design, annealing of the processed sample, cross CGP, ring CGP, hybrid SPD, covered sheet casing CGP, and rubber pad CGP, are emerging techniques to up-scale the procedure and improve the grain refinement and thereby produce superior mechanical properties. In this review paper, the historic research of conventional CGP and its effect on grain refinement and mechanical properties is initially briefed and then recent progress through different advanced techniques is highlighted, especially in alloys. Albeit significant progress has been observed in CGP, the future scope and successful usage of CGP-processed samples in actual practice are discussed in the last stage.

Numerical-experimental study of die geometry in the constrained groove pressing of 6061 aluminum sheets

Nowadays, in line with the need of different industries to the materials with high strength to weight ratio, researchers have drawn attention to the processes of severe plastic deformation. The constrained groove pressing (CGP) is one of the most effective methods of severe plastic deformation to produce high-strength sheet metal using two dies with different shapes (grooved and flat). Despite the advantages of CGP in creating high accumulative plastic strain, this process leads to non-uniformity in mechanical properties of the sheet. This non-uniformity is one of the limitations of the CGP process which is considered in this study. Experimental and numerical studies were performed to investigate CGP process on 6061 aluminum alloy sheet up to two complete passes and the mechanical properties of the sheets were studied. Hardness testing was conducted on the worked material and the increase in the hardness of tested material in both longitudinal and thickness directions were observed. Also, it was shown that the non-uniformity in hardness distribution is correlated to the non-uniformity in the strain distribution. So, validated numerical model was used to develop the response surface method (RSM) and consequently to investigate the effect of geometric parameters in the grooved die on the strain uniformity. Finally, die geometry was optimized using the developed RSM model to produce a sample with more uniformity in strain and hardness distribution.

Friction stir welding of severely plastic deformed aluminum using (Al2O3 + graphite) hybrid powders: grain structure stability and mechanical performance

Welding of severely plastic deformed aluminum sheets, with high stored strain energy, faces a serious concern, which is decrease in strength of weld and heat-affected zone (HAZ) due to instability in microstructure and related grain growth. In this work, two-passes constrained groove pressed (CGPed) Al-1050 sheets were welded via friction stir welding (FSW), without and with addition of a hybrid powder including 50 vol.% α-Al2O3 nanoparticles+50 vol.% graphite micrometric powders (∼1 vol.% of hybrid powders in stir zone). Al2O3 nanoparticles may result in grain refinement in stir zone by grain boundary pinning. Lubricating nature of graphite may reduce welding heat input resulting in lower degree of HAZ softening. Addition of hybrid powders improved thermal stability of grain structure and increased hardness of stir zone and strength of weld after three passes of FSW and at high rotation speed (ω) to traverse speed (v) ratio. With one-pass FSW, a sound weld was not achieved. However, higher weld efficiency (with transition of failure location from stir zone to HAZ) was obtained when three-pass FSW was carried out due to better material flow, superior distribution of powders, and elimination of cavities. Due to presence of graphite, effect of increase in pass number was negligible on HAZ softening. Finer distribution of hybrid powder was achieved at high ω/v ratios. Weld efficiency was improved from ∼50% (strength of 62 MPa) in one-pass FSW at ω/v = 25 r/mm to a maximum of ∼80% (strength of 101 MPa) after conducting three-pass FSW at ω/v = 70 r/mm.

Friction stir welding of severely deformed copper sheets: microstructure and mechanical properties

Friction stir welding (FSW) was performed at different tool rotation speeds of 1250 and 1600 rev min−1 on both annealed, and severely plastic deformed copper sheets via constrained groove pressing (CGP). Also, the effects of water cooling during FSW on weld properties of CGP-treated samples were investigated. It is found that the heat-affected zone (HAZ) has a lower hardness value than the corresponding base metal due to the large grain growth. While the stir zone (SZ) shows a finer grain size with a higher hardness. Moreover, the results proved that in-process water cooling can effectively reduce grain growth in HAZ of CGPed samples and improve the weld strength by increasing the minimum hardness to about SZ hardness of the annealed sample.

Microstructural evolution during short heat treatment of constrained groove pressed Cu‐5%Zn alloy

Severe plastic deformation (SPD) is a widely used technique to obtain superior material properties specially mechanical properties. Constrained groove pressing (CGP) is found to be the most attractive SPD technique for the deformation of sheets and plates. However, this technique results in microstructural inhomogeneity during processing. The microstructural inhomogeneity can be alleviated by employing a thermal cycle, which assists in controlled recovery and recrystallisation. The current work focuses on, the microstructure evolution of one pass as-deform CGP sample followed by a short heat-treated (SHT). A correlative imaging technique of transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM) showed the presence of dislocation cell structure in an as-deformed condition. The short heat treatment resulted in the transformation of the dislocation cell wall to high-angle boundaries, with a further increase in heat-treatment time resulting in grain growth.