Continuous Confined Strip Shearing Research Articles

The effect of continuous confined strip shearing deformation on the mechanical properties of AZ31 magnesium alloys

Continuous confined strip shearing deformation (CCSS) was conducted on AZ31 magnesium alloys. The microstructure and texture were modified and special inclined basal texture was obtained through different routes. The newly formed basal texture was favor for the basal slip which brought about lower micro-hardness and yield strength but higher elongation. The strong tensile-compression asymmetry in the base material was weakened because basal slip was the dominating deformation mechanism both in tensile and compression tests. Meanwhile, {10-12} twinning was suppressed because of easier activation of basal slip. The strain hardening behavior was also changed and the strain hardening rate almost decreased along the whole deformation process; and only a slight increase was found at the stage2 of route A in tensile test. The strain hardening exponents were scattered from different stages due to the specific deformation mechanism at each stage.

Influence of Rolling Reduction Ratio on Continuous Confined Strip Shearing Deformation Procedure Using Finite Element Analysis

The severe plastic deformation (SPD) procedure designated continuous confined strip shearing (CCSS/C2S2) technique based on rolling, equal channel angular pressing (ECAP) and Conform principle was simulated numerically by using finite element code DEFORM-3D. The influences of rolling reduction ratio on restoration ratio of work-piece geometry, effective strain, output velocity of processed work-piece, torque of rollers, and energy consumption feature for the C2S2 procedure were investigated. The results show that rolling reduction ratio has significant influences on C2S2 procedure. With the increase of rolling reduction ratios (5%, 10% and 20%), the restoration ratio of work-pieces geometry reduced, the magnitude of effective strain kept almost unchanged, the output velocity of processed work-piece increased, the total torque of rollers decreased, and the energy consumption used for making unit volume work-piece subjected to unit straining reduced considerably. It was found that the optimal rolling reduction ratio was about ~10 %, where the energy consumption reduced by 8.16 %, whereas the restoration ratio of work-piece geometry was almost the same as constrasting with the rolling reduction ratio of 5 %.

Stability against coarsening in ultra-fine grained aluminum alloy AA 3103 sheet fabricated by continuous confined strip shearing

The stability of ultra-fine grained Al–Mn alloy AA 3103 against coarsening at elevated temperature is analyzed. AA 3103 sheets were produced by means of continuous confined strip shearing (CCSS), which represents an adaptation of equal channel angular pressing to impose severe plastic deformation on sheet samples. With increasing number of CCSS passages, finer and more uniform grains with an increasing fraction of high-angle grain boundaries (HAGBs) were observed. In particular, the sample subjected to 12 passages of CCSS displayed fairly uniform equiaxed grains with an average size of 1.6 μm. During subsequent annealing at 300 and 350 °C, these grains were quite stable, exhibiting a rather low growth rate. This stability is explained in terms of Humphreys’ unified theory of the stability of cellular structures, which has shown that under conditions of very large strains when HAGBs prevail intrinsically stable microstructure will be formed.

Numerical investigation of aluminum deformation behavior in three-dimensional continuous confined strip shearing process

Bulk ultra-fine-grained materials can be obtained by equal channel angular pressing (ECAP) process. A new metal forming process called as continuous confined strip shearing (CCSS/C2S2) process based on ECAP and Conform process was introduced in this paper for fabricating aluminum alloy sheets with a high formability. The C2S2 process was simulated numerically by using DEFORM-3D and the deformation behavior of the pure aluminum sheets was studied. The influences of die geometric parameters such as the die channel angle and the die outer corner angle on the material deformation were given. In addition, the effect of the friction on the die–workpiece interface on the effective strain change in the C2S2 process was investigated. The obtained numerical simulation results provide valuable guidelines for C2S2's die design, determination of process parameters and process planning.

Evolution of textures and microstructures in IF-steel sheets during continuous confined strip shearing and subsequent recrystallization annealing

Interstitial free (IF) steel sheets were deformed by continuous confined strip shearing (CCSS) based on the equal channel angular pressing (ECAP). The samples were deformed by CCSS up to three passages and subsequently recrystallized at 700°C for 1 h. The strain history of IF steel sheets in the CCSS die-channel was tackled by finite element method (FEM) simulations. The deformation by CCSS led to the shear deformation and consequently the formation of shear texture components. With increasing number of CCSS passages, the intensity of the deformation texture was hardly increased. The recrystallization texture resembled the deformation texture. The orientation stability was discussed by mean of Taylor deformation model and the formation of recrystallization textures was discussed by occurrence of the discontinuous recrystallization. Observations by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) revealed the formation of ultra-fine grains in IF sheets deformed by CCSS.

Effect of accumulative strain on texture evolution in 1050 Al alloys processed by continuous confined strip shearing

Abstract The effect of the accumulative strain on texture evolutions in 1050 aluminum alloy processed by dissimilar channel angular pressing (DCAP) was investigated. Very high plastic strain ( e eff ∼ 19) were imparted into the materials via multiple passages ( N = 32) through the DCAP die. The intensities of the texture components after DCAP depended on the accumulative strain for low applied strain ( e eff e eff > 5.8), there was no significant change in intensity.

Formation of a random texture and ultrafine grains in AA 3003 aluminium alloy during the repeated shear deformation introduced by continuous confined strip shearing

To investigate the microstructural development and corresponding texture evolution during repeated shear deformation, specimens of AA 3003 Aluminium alloy were deformed by continuous confined strip shearing based on equal channel angular pressing. Strip specimens were deformed by the shear forming process during up to eight passes, equivalent to effective strains of ~4.8. Texture evolution in the AA 3003 strips during the shear deforming process was studied by comparing the experimentally measured textures with simulated ones. Electron backscattered diffraction was employed to investigate detailed changes in microtextures and microstructures during repeated shear deformation. Softening associated with deformation is believed to be responsible for the formation of ultrafine grains and the random texture resulting from repeated shear deformation.

Effect of initial textures on texture formation in AA 3004 sheets during continuous confined strip shearing and subsequent annealing

The effect of initial textures on the texture formation during continuous confined strip shearing (CCSS) and subsequent annealing was investigated in AA 3004 sheets. The CCSS tools were designed to provide a constant shear strain of the order of 0.5 per pass while preserving the original sheet shape. During the CCSS deformation, the initial texture disappeared, and shear texture components developed. However, the intensity of the shear texture components did not further develop with an increasing number of CCSS passes. The softer initial sample depicting the cube texture displayed the evolution of {111}//ND fiber orientations. Upon recrystallization annealing, the textures developed during CCSS were randomized through the suppression of oriented nucleation and selected growth which generally dominate the evolution of recrystallization texture in cold rolled aluminum alloy sheets.

Effect of initial texture on texture evolution in 1050 Al alloys under simple shear

The effect of the initial textures prior to dissimilar channel angular pressing (DCAP) on the texture evolution of the 1050 Al alloy sheets, processed by the continuous confined strip shearing (C2S2) process, were studied. The four different specimens, i.e., cold rolled, heat treated, warm rolled, and as-cast 1050 Al alloy sheets, having various initial textures were prepared using different thermomechanical routes. Although the major texture types were significantly affected by the initial textures prior to DCAP, DCAP always promoted both the 〈111〉//normal direction (ND) textures and the {001}〈110〉 rotated cube texture regardless of the initial texture status. Effects of the texture evolutions due to equal channel angular pressing (ECAP) on deep drawbility and planar anisotropy were analyzed based on the -r value and the Δr value determined from the measured pole figures. A feasibility for producing the 1050 Al alloy sheets having high deep drawbility and low planar anisotropy was demonstrated.

Microstructural evolutions of the Al strip prepared by cold rolling and continuous equal channel angular pressing

A new metal forming technique termed the continuous confined strip shearing (C2S2) process based on equal channel angular pressing (ECAP) is introduced. Unlike the conventional batch-type ECAP process dealt in the earlier studies, the developed technique enables sheet forming in a continuous mode and in a repeatable manner. Likewise rolling, the developed process is able to control the mechanical properties of the material through the multipass operation. Both hardening and softening mechanisms in ECAP were investigated by correlating the measured hardness with microstructural evolutions of the Al specimens using transmission electron microscopy. The process conditions required to produce the fine-grained structure were suggested in terms of the strain per passage and the total strain imparted to the specimens. The effect of the temperature on the accelerated grain refining during the continuous ECAP operation was discussed.

Texture evolution of the strip cast 1050 Al alloy processed by continuous confined strip shearing and its formability evaluation

Studies on texture evolutions were conducted on strip cast 1050 Al alloy sheets to assess the feasibility of equal channel angular pressing (ECAP) and subsequent heat treatments as a means for enhancing the formability while reducing the earing of the sheets. ODFs were calculated to investigate texture evolutions due to ECAP and subsequent heat treatments. The r ̄ -value and Δ r-value were determined based on the measured pole figures to judge the formability and the earing of the samples. Experiments showed that the production of the 1050 Al alloy sheets with high formability ( r ̄ =1.05) and low earing (Δ r=0.05) could be possible by ECAP and the heat treatment at appropriate temperature.

Controlling the textures of the metal strips via the continuous confined strip shearing(C2S2) process

A new concept process, a so-called as C2S2 process based on equal channel angular pressing, for fabricating the A1 alloy sheets with a high formability is introduced. The C2S2 machine was designed so that it can feed the metal strip in a continuous manner at a relatively high speed in the range of ∼20 m/min. A significant amount of the shear deformation could be achieved by passing the sample through the ECAP die with Φ = 120°. The pole figures were calculated both to demonstrate the evolution of the textures of the 1050 A1 alloy sheets and to elucidate the feasibility of the proposed process as a means for enhancing the formability of the metal strips.