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CoCuFeMnNi complex concentrated alloy was subjected to hot compression at different temperatures and strain rates. Texture evolution for four representative samples was studied using electron backscatter diffraction, neutron diffraction and viscoplastic self-consistent simulations. EBSD revealed highest low angle grain boundaries and high angle grain boundaries for sample C (1273 K, 1 s−1) indicating deformation and recrystallization, respectively, and highest very low angle grain boundaries for sample D (1273 K, 0.001 s−1) indicating recovery. The bulk texture shows < 110 > compression texture, with dominance of partial slip over octahedral slip. Zener–Hollomon parameter was found to increase in the order D < B < C < A, with sample A (1073 K, 1 s−1) exhibiting lowest crystallite size and sample D (1273 K, 0.001 s−1) with highest crystallite size, consistent with the microstructural data. The texture analysis shows a partial slip-dominated dynamically recovered microstructure for sample A (1073 K, 1 s−1) and discontinuous dynamically recrystallized microstructure for sample D (1273 K, 0.001 s−1). [ABSTRACT FROM AUTHOR]

Mechanical responses of cold pilgered Zircaloy-4 (Zr-4) tubes are measured under different uniaxial (tension/compression) loading directions. Tensile tests were carried out along three directions: rolling direction (RD), transverse direction (TD) and 45° to the rolling direction (45RD) at quasi static strain rate. Compression test was also performed in the RD. Texture was characterized at intermediate strains with electron backscattered diffraction method. For different uniaxial loading conditions, anisotropic yield stress and strain hardening behavior can be observed. Such complex mechanical behavior is well explained with the variations in activation of deformation mechanisms predicted by the Schmid factor distribution and visco-plastic self-consistent (VPSC) model. In order to calibrate the VPSC model's parameters more accurately, both mechanical responses and texture changes for four different directional tests are compared with VPSC simulations. The calculated Lankford coefficients are also calibrated with anisotropic tensile results. Furthermore, a deepening understanding of the texture evolution under different loading directions were disclosed based on VPSC method. The results indicate that the activity of deformation mechanisms changes significantly with different uniaxial loading directions. Non-prismatic slips with higher critical resolved shear stress, e.g. basal and pyramidal slip, make larger contributions to the yield and strengthening stress resulting in the highest stress in TD compared with RD and 45RD. Compression test along RD prefers the activation for tensile twinning (TTW). Meanwhile, TTW can be detected in 45RD and TD tension owing to the spread distribution of initial texture towards TD. [ABSTRACT FROM AUTHOR]

The strain hardening is an effective mode of enhancing mechanical properties in alloys. In this work, the strain hardening behaviors of Mg- x Y (x = 1, 2, and 3 wt%) after extrusion process was investigated using uniaxial tensile tests. Results suggest that the Mg– x Y alloys are composed of α-Mg with a little amount of Mg 24 Y 5 phase. The average grain size reduces from 19.8 µm to 12.2 µm as the Y content adds from 1 wt% to 2 wt%. Nevertheless, when Y content reaches 3 wt%, the grain size reaches to 12.9 µm, which is close to that of Mg–2Y. The strain hardening rate decreases from 883 MPa to 798 MPa at (σ – σ 0.2) = 40 MPa, and Mg–2Y and Mg–3Y have the similar strain hardening response. Moreover, Mg–1Y shows an obvious ascending stage after the steep decreasing stage, which is mainly caused by the activation of twinning. The strain hardening behavior of Mg– x Y is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent (VPSC) model. The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture. [ABSTRACT FROM AUTHOR]

Based on the stress characteristics of the instantaneous cross-section deformation of the wall reducing section during the cold rolling of two-roll Pilger pipes, the rectangular samples with 0° and 90° to the extrusion direction (ED) were cut from the extruded AZ31 magnesium alloy bar for 3% pre-deformation test to simulate its stress state equivalently. The sample was then cut from the pre-deformed sample by wire cutting for secondary compression, and the sample that is not pre-deformed is selected. The mechanical behavior and texture evolution of AZ31 magnesium alloy under different loading conditions were respectively studied by EBSD experiment and VPSC simulation. Results show that the true stress–strain curve and texture evolution characteristics of AZ31 magnesium alloy during the secondary compression process are in good agreement with the prediction of the VPSC model. The secondary compression behavior can be effectively explained by the relative activity of the deformation modes. The pre-deformation in the ∥ED (⊥ED) direction is conducive to the shift of the pole density of the {0001} basal surface texture to the positive and negative directions of the ED (TD). The pre-deformed sample exhibits a higher yield strength than the non-pre-deformed sample in the same loading direction. The high ductility of magnesium alloys can be achieved by activating pyramidal 〈c + a〉 slippage.

Severe plastic deformation is a technical method to produce functional material with special properties such as high strength and specific physical properties. Selection of an efficient severe plastic deformation for grain refinement is a challenging field of study and using a modeling technique to predict the refinement efficiency has gained a lot of attentions. A comparative study was carried out on the grain refinement ability of two severe plastic deformation techniques. Accordingly, beta-tin samples were processed for almost the same strain level by the equal channel angular extrusion (ECAE) and the newly developed multi-axial incremental forging and shearing (MAIFS). Optical microscope and tensile tests were used to investigate the microstructure and mechanical properties. It was found that the MAIFS process is more efficient in grain refinement than ECAE by help of crystal plasticity analysis and experimental observation. This was ascribed to the more activated slip systems in MAIFS than ECAE and activation of secondary modes of deformation in MAIFS. The conclusion was supported by the finer grains that was observed in the sample processed by MAIFS and compared with grain size of the sample processed by ECAE. Finally, these observations were related to materials flow for beta-Tin during tensile test.

In the present work, Ca-induced plasticity of AZ31 magnesium alloy was studied using electron backscattered diffraction (EBSD) measurements supported by viscoplastic self-consistent (VPSC) calculations. For this purpose, alloy samples were stretched to various strains (5%, 10%, and 15%) at room temperature and a strain rate of 10−3 s−1. The EBSD measurements showed a higher activity of non-basal slip system (prismatic slip) as compared to that of tension twins. The VPSC confirmed the EBSD results, where it was found that the critical resolved shear stress of the various slip systems and their corresponding activities changed during the stretching of the alloy samples.

There is currently a significant scientific and industrial interest in developing material models for the simulation of plastic deformation of aluminum extrusions relevant to their forming and their response during in service events such as vehicle crash. The objective of this work is to evaluate the effect of through thickness crystallographic texture gradients on material mechanical behaviour. This has been studied using a combination of experiments (i.e. pilot scale extrusions and stress-strain curves with the R-value to characterize plastic anisotropy for different loading directions) and the visco-plastic self-consistent (VPSC) polycrystal plasticity simulations on a model alloy system. Two limiting conditions were examined, i.e. unrecrystallized and fully recrystallized conditions. The results of electron backscatter diffraction (EBSD) characterization show that there is a significant through thickness variation in texture for both cases. However, the implications of the texture gradient on the macroscopic plastic response were relatively minor for the unrecrystallized case but quite significant for the recrystallized case. This was manifested as a strong difference in the contraction of the surface layer compared to the centre of the extrudate, particularly in the case of tests at 45° and 90° to the extrusion direction. This was rationalized in terms of the differences in texture between the surface and the centre using VPSC simulations. Finally, it was proposed that this effect will be explored in future work as it may have important implications on the surface stress state which could affect damage initiation, growth and coalescence, particularly in bending situations. [ABSTRACT FROM AUTHOR]

In the present investigation, the dependence of deformation mechanisms on quaternary alloying addition has been investigated for medium Mn austenitic steel. A steel with composition Fe-12Mn-0.5C-X (X: Ni and Al), a medium Mn austenite steel was deformed up to 60% by cold reduction to investigate the deformation mechanisms and texture evolution. Electron Back-scattered Diffraction (EBSD) and X-ray bulk texture measurement have been performed to study the deformation behaviour. Deformed microstructure with increasing strain was systematically analyzed with respect to the alloying addition. SFE of the alloy can be tailored by the addition of alloying elements. In the present investigation, SFE has been tailored by addition of Carbon, Aluminium and Nickel. The highest deformation twin fraction has been observed in Ni added sample and the lowest in the Al-added sample. Visco plastic self-consistent (VPSC) simulation has been performed to understand the contribution of slip and twin activity during deformation. [ABSTRACT FROM AUTHOR]

A combination of electron back–scattering diffraction and visco–plastic self–consistent (VPSC) –based dynamic recrystallisation (DRX) modelling was used to investigate the texture evolution in a Ni–30Fe–Nb–C model alloy subjected to hot plane strain compression to a true strain of 1.2 at temperatures of 925 °C and 1075 °C. Typical of hot rolled face centred cubic materials (in the absence of DRX), deformation at 925 °C led to the development of β–fibre orientations along with a weaker Cube ({001}〈100〉) component. This Cube orientation intensifies and dominates the final texture with the occurrence of DRX during deformation at 1075 °C. The VPSC model successfully predicted the experimental textures at 925 °C (without DRX) and 1075 °C (with DRX), by accounting for non–octahedral {011}〈110〉 slip activity at high temperatures and by using a physically more realistic grain–matrix interaction scheme intermediate between the Taylor and Sachs models. Our simulations show that the dominance of the Cube orientation in the DRX texture at 1075 °C can be ascribed to its higher stored energy and subsequently higher probability of nucleation, combined with its stabilisation due to the activation of non–octahedral {011}〈110〉 slip. [ABSTRACT FROM AUTHOR]

Formability and viscoplastic self-consistent simulations of Mg-4Zn-X-Ca alloys were carried out in an effort to understand the relationship between deformation behaviors and room-temperature formability. The microstructural, textural and mechanical properties of Mg-4Zn-X-Ca alloys were also investigated. All of the alloys showed a sound twin roll cast microstructure without the occurrence of inverse segregation. Annealed Z4 and ZSX400 alloys exhibited strong basal textures; however, the other Mg alloys showed weaker basal textures with splitting in the transverse direction resulting from their different types of static recrystallization. Among the Mg-4Zn-X-Ca alloys, the ZAX400 alloy exhibited a high yield strength value of 189.3 MPa and excellent formability of 7.5 mm with enhanced yield isotropy, comparable to those of Al alloys. The higher formability values of the Mg-4Zn-X-Ca alloys were closely related to the modified deformation behaviors resulting from the texture evolution. The ZX40, ZAX400, ZWX400 and ZCX400 alloys, which were more formable, had higher relative activity of the basal slip upon compression deformation, thus improving the yield isotropy. However, the Z4 and ZSX400 alloys in this study, had relatively low activity of the basal slip in compression modes, as caused by their different CRSS ratios (tension twin/basal slip). [ABSTRACT FROM AUTHOR]

Modeling the effect of deformation twinning and the ensuing twin-twin- and slip-twin-induced hardening is a long-standing problem in computational mechanical metallurgy of materials that deform by both slip and twinning. In this work, we address this effect using the twin volume transfer method, which obviates the need of any cumbersome criterion for twin variant selection. Additionally, this method is capable of capturing, at the same time, secondary or double twinning, which is particularly important for modeling in large strain regimes. We validate our modeling methodology by simulating the behavior of an Fe-23Mn-1.5Al-0.3C twinning-induced plasticity (TWIP) steel under large strain conditions, experimentally achieved in this work through equal-channel angular pressing (ECAP) for up to two passes in a 90° die following route BC at 300 °C. Each possible twin variant, whether nucleating inside the parent grain or inside a potential primary twin variant was predefined in the initial list of orientations as possible grain of the polycrystal with zero initial volume fraction. A novelty of our approach is to take into account the loss of coherency of the twins with their parent matrix under large strains, obstructing progressively their further growth. This effect has been captured by attenuating growth rates of twins as a function of their rotation away from their perfect twin orientation, dubbed here as “disorientation” with respect to the mother grain’s lattice. The simulated textures and the hardening under tensile strain showed very good agreement with experimental characterization and mechanical testing results. Furthermore, upper-bound Taylor deformation was found to be operational for the TWIP steel deformation when all the above ingredients of twinning are captured, indicating that self-consistent schemes can be bypassed.

In this study, the solidification and deformation behaviors in twin roll cast (TRC) Mg-6Al-X alloys have been investigated. The TRC simulation results showed that the AX60 alloy tended to have lower segregation while the AZ60 had the highest segregation due to the different solidification behavior and thermal properties. Compared to the as-cast microstructure, the segregation area was well matched with the melt to roll nip distance predicted in simulation. Mg alloys with Ca or Sr elements showed weaker textures when compared to A6 alloys rolled at 350 °C. In addition, there was a significant change in (0002) pole figures from strong basal textures to random textures when the rolling temperature increased from 350 °C to 450 °C. This may be attributed to the non-basal slip system activity at high temperatures. The results of visco-plastic self-consistent simulation revealed that critical resolved shear stress of the tension twin increased with increasing rolling temperature. This led to tension twin suppression in compression, which were associated with enhancing the yield isotropy of Mg alloys. Furthermore, the relative activities of basal slip in AX60 alloy were higher than the other Mg alloys. This means they were responsible for enhancing the formability and yield isotropy of Mg alloys. [ABSTRACT FROM AUTHOR]

• Acousto-plasticity was modeled considering nonuniform softening among slip systems. • The model implemented in VPSC was validated on micro-tensile tests of pure copper. • Model suggests softening is not homogenous and is dependent on grain orientation. • Higher stress reduction is predicted in grains with high Taylor factor. In this study, a novel approach to modeling the ultrasonic softening effect during metal plasticity is developed, where the slip systems experience differential softening depending on their orientation relative to the ultrasonic direction. The directional softening model was implemented within a Visco-Plastic Self-Consistent (VPSC) model, where the material and ultrasonic softening parameters are calibrated based on micro-tensile test data of pure copper with tension along the rolling direction of sheet. The model is then validated against the stress-strain response of the samples with tension along transverse direction. The VPSC modeling results provide new insights into ultrasonic softening, particularly that the stress reduction is not homogeneous in the whole aggregate. The degree of softening shows a strong dependence on grain orientation. A higher level of stress reduction is observed in plastically hard, high Taylor factor grains. A decrease in Taylor factor is predicted, especially in the grain subset with higher stress reduction, which agrees with experimental data. Although a traditional isotropic softening model is also capable in predicting the ultrasonically softened stress-strain response for different texture inputs, this decrease in Taylor factor cannot be captured. [ABSTRACT FROM AUTHOR]

X-ray diffraction was used to track the evolution of texture in a fully recrystallized Fe-24Mn-3Al-2Si-1Ni-0.06C TWinning Induced Plasticity steel subjected to uniaxial tensile testing. The bulk texture measurements returned the characteristic double fiber for fcc materials with a relatively stronger 〈111〉 fiber and a weaker 〈100〉 fiber parallel to the tensile axis. The Visco-Plastic Self-Consistent model was used to simulate the macroscopic stress-strain response as well as to track the evolution of the bulk crystallographic texture by detailing the contribution of slip and twinning when latent hardening effects are excluded or included. The simulations revealed the dominant role of slip and the limited volume effect of twinning on the overall development of the bulk texture. The correlation between the latent hardening effects and the employed grain interaction scheme is highlighted. [ABSTRACT FROM AUTHOR]

Abstract: A combination of X-ray diffraction and visco-plastic self-consistent (VPSC) modelling was used to track the texture evolution in an Fe–28Mn–0.28C twinning-induced plasticity steel subjected to cold-rolling between 12% and 80% thickness reduction. Texture measurements returned the characteristic α-fibre for low stacking fault energy face-centred-cubic materials along with a weaker γ-fibre. VPSC modelling has been used to simulate real-world rolling conditions by simultaneously approximating the composite deformation pattern in heavily twinned and untwinned (or sparsely twinned) grains and empirically accounting for the usually overlooked, redundant shear effect. When the above two factors are combined with a grain–matrix interaction scheme that approaches a Sachs-type model, the evolution of the Goss and Brass orientations on the α-fibre is well captured and for the first time, the F orientation along the γ-fibre is successfully predicted. [Copyright &y& Elsevier]

Abstract: An additional length scale is introduced which is not considered by the existing Taylor or viscoplastic self-consistent (VPSC) models. In these models, a macroscopic deformation is imposed on a representative volume element (RVE) of the macroscopic length scale (∼1000 grains). Each grain constitutes a RVE at what will be called the “mesoscopic-1” length scale. Here an additional intermediate length scale is introduced, called “mesoscopic-2”. Its RVE is a “cluster” of several grains. Within each cluster, the algorithm of the Neffect-VPSC model is employed to treat grain interactions. The average deformation of each cluster is the macroscopic deformation. This model gives texture predictions as good as, or better than, the Neffect-VPSC or the ALAMEL models for several tested materials and kinds of tests. The Taylor, VPSC and the ALAMEL models can be seen as special versions of such cluster-type model. The Taylor and the VPSC models were then tested to give two bounds of the predicted total slip rate in the aggregate for rolling. The total slip rate is proportional to the predicted von Mises equivalent stress of the aggregate. The difference among these model predictions was studied statistically by plotting the x-value distribution as defined and discussed in this paper. It seems that according to a cluster model simulation for rolling, statistically the strain rates of the hard grains defined in this paper tend to reduce less than the increase in the strain rate of soft grains in the direction of the imposed strain rate; gradually this diminution/increase reduces for both hard and soft grains as deformation increases. We call these diminution/increase “relaxations”. Relaxations projected on the five bases in the 5-D plastic strain rate space for rolling indicate that different numbers of grains in each cluster correspond to different levels of relaxations. [Copyright &y& Elsevier]

Abstract: Two micro–macro scale transition models, namely the ALAMEL and visco-plastic self-consistent (VPSC) models (both predict the evolution of grain shape and texture), were used to study the effect of the initial grain shape. The evolution of plastic anisotropy was characterized by the q-value and was simulated in three directions for three low carbon steels assuming either equiaxed (hypothetical one) or a pancake (measured one) grain shape. In addition, texture evolution during rolling was investigated for one of the materials. Comparisons between the model predictions and the measured values demonstrate that the grain shape effect can be predicted well by both models. In most cases, the initial q-value can be nicely estimated by both models. VPSC is better than ALAMEL on q-value evolution prediction for simulations which consider the measured aspect ratios. For texture evolution of rolling, the effect of initial grain shape is only significant at large deformation. [Copyright &y& Elsevier]

Abstract: A combination of electron back-scattering diffraction and X-ray diffraction was used to track the evolution of the microstructure and texture of a fully recrystallized Fe–24 Mn–3 Al–2 Si–1 Ni–0.06 C twinning-induced-plasticity steel during interrupted uniaxial tensile testing. Texture measurements returned the characteristic double fibre texture for face-centred cubic materials, with a relatively stronger 〈111〉 and a weaker 〈100〉 partial fibre parallel to the tensile axis. The interaction with the stable 〈111〉 oriented grains results in preferential plastic flow in the unstable 〈110〉 oriented grains. Consequently, the grains oriented along the 〈110〉 and 〈100〉 fibres record the highest and lowest values of intragranular local misorientation, respectively. The viscoplastic self-consistent model was used to simulate the macroscopic stress–strain response as well as track the evolution of bulk crystallographic texture by detailing the contributions of perfect and/or partial slip, twinning and latent hardening. The simulations revealed the dominant role of perfect slip and the limited volume effect of twinning on the texture development. The effects of initial orientation and grain interaction on the overall orientation stability during uniaxial tension showed that while the 〈100〉 fibre remains stable and does not affect the unstable orientations along the 〈110〉 fibre, the orientations along the stable 〈111〉 fibre strongly affect the unstable 〈110〉 orientations. [Copyright &y& Elsevier]

Abstract: The effects of initial texture and strain path (tension and compression) on the work hardening and texture evolution have been studied in an AZ80 alloy deformed at 77K and 293K. Crystal plasticity simulations have been used to interpret slip and twinning activity based on these experiments and a systematic and physically based approach has been used to fix the adjustable slip and twinning system parameters. These combined experiments and simulations indicate that the work hardening rate is significantly affected by temperature, the high hardening rate at 77K being interpreted as resulting from a combination of texture hardening and reduced dynamic recovery. For conditions where slip is expected to be the dominant deformation mechanism, simulations and experiments are in excellent agreement, while agreement with twinning dominated test conditions are hindered by the ability to predict accurately the twinning kinetics. [Copyright &y& Elsevier]

Abstract: The stress–strain curves of drawn tungsten wires exhibit a strong tension–compression asymmetry, which is demonstrated experimentally for a series of wires drawn to different diameters. The phenomenon is explained as a consequence of crystallographic texture. Texture evolution is modelled using a visco-plastic self-consistent (VPSC) model. In a tensile test, the straining direction remains the same as during wire drawing, and therefore the 〈011〉 fibre texture continues to evolve. In the compression test, on the other hand, the straining direction is reversed and the fibre texture is transformed into a 〈111〉 texture. This is accompanied by transient softening or at least reduced hardening during compression, a prediction which qualitatively agrees with the experiments. The influence of latent hardening on the amount of softening during strain reversal is also investigated. [Copyright &y& Elsevier]

The article evaluates the two different approaches of twin modeling in self-consistent texture simulation of twinning induced plasticity steels. According to the authors, the twinning models have been implemented within the framework of the viscoplastic self-consistent model. The salient features of the predominant twin reorientation scheme and the Kalidindi model are described.

Abstract: At near ambient conditions, CaIrO3 is isostructural with the high-pressure polymorph MgSiO3 “post-perovskite” (pPv). MgSiO3 pPv is thought to be a major phase in the earth''s lowermost mantle. CaIrO3 can thus serve as an analog for studying deformation of the pPv phase under conditions achievable with a multi-anvil deformation apparatus. Here we study the rheologic behavior of CaIrO3 pPv at a variety of pressure and temperature conditions from 2 GPa to 6 GPa and 300 K to 1300 K and various strain rates. Sintered, polycrystalline CaIrO3 pPv, cylindrical in shape, was deformed in the D-DIA multi-anvil press in several shortening cycles up to 20% axial strain at each temperature and pressure. Shortening cycles were followed by lengthening back to 0% strain. Quantitative texture information was obtained using in-situ synchrotron X-ray diffraction and the Rietveld method to analyze images. In all cases we find that (010) lattice planes align perpendicular to the compression direction upon shortening, and that there is little change in texture with temperature or pressure. This texture pattern is consistent with slip on (010)[100]. The texture observed here is different from that produced in room temperature diamond anvil cell (DAC) experiments on MgGeO3 and MgSiO3 pPv which both display textures of (100) and {110} lattice planes at high angles to the compression direction. This implies that CaIrO3 pPv may not be a good analog for the plastic behavior of MgSiO3 pPv. [Copyright &y& Elsevier]

In the present work, Ca-induced plasticity of AZ31 magnesium alloy was studied using electron backscattered diffraction (EBSD) measurements supported by viscoplastic self-consistent (VPSC) calculations. For this purpose, alloy samples were stretched to various strains (5%, 10%, and 15%) at room temperature and a strain rate of 10−3 s−1. The EBSD measurements showed a higher activity of non-basal slip system (prismatic slip) as compared to that of tension twins. The VPSC confirmed the EBSD results, where it was found that the critical resolved shear stress of the various slip systems and their corresponding activities changed during the stretching of the alloy samples. [ABSTRACT FROM AUTHOR]

Modeling the effect of deformation twinning and the ensuing twin-twin- and slip-twin-induced hardening is a long-standing problem in computational mechanical metallurgy of materials that deform by both slip and twinning. In this work, we address this effect using the twin volume transfer method, which obviates the need of any cumbersome criterion for twin variant selection. Additionally, this method is capable of capturing, at the same time, secondary or double twinning, which is particularly important for modeling in large strain regimes. We validate our modeling methodology by simulating the behavior of an Fe-23Mn-1.5Al-0.3C twinning-induced plasticity (TWIP) steel under large strain conditions, experimentally achieved in this work through equal-channel angular pressing (ECAP) for up to two passes in a 90° die following route BC at 300 °C. Each possible twin variant, whether nucleating inside the parent grain or inside a potential primary twin variant was predefined in the initial list of orientations as possible grain of the polycrystal with zero initial volume fraction. A novelty of our approach is to take into account the loss of coherency of the twins with their parent matrix under large strains, obstructing progressively their further growth. This effect has been captured by attenuating growth rates of twins as a function of their rotation away from their perfect twin orientation, dubbed here as “disorientation” with respect to the mother grain’s lattice. The simulated textures and the hardening under tensile strain showed very good agreement with experimental characterization and mechanical testing results. Furthermore, upper-bound Taylor deformation was found to be operational for the TWIP steel deformation when all the above ingredients of twinning are captured, indicating that self-consistent schemes can be bypassed. [ABSTRACT FROM AUTHOR]