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In directional forming processes, such as rolling and extrusion, the grains can develop preferred crystal orientations. These preferred orientations—the texture—are the main cause for material anisotropy. This anisotropy leads to phenomena such as earing, which occur during further forming processes, e.g., during the deep drawing of sheet metal. Considering anisotropic properties in numerical simulations allows us to investigate the effects of texture-dependent defects in forming processes and the development of possible solutions. Purely phenomenological models for modeling anisotropy work by fitting material parameters or applying measured anisotropy properties to all elements of the part, which remain constant over the duration of the simulation. In contrast, crystal plasticity methods, such as the visco-plastic self-consistent (VPSC) model, provide a deeper insight into the development of the material microstructure. By experimentally measuring the initial texture and using it as an initial condition for the simulations, it is possible to predict the evolution of the microstructure and the resulting effect on the mechanical properties during forming operations. The results of the simulations with the VPSC model show a good agreement with corresponding compression tests and the earing phenomenon, which is typical for cup deep drawing. [ABSTRACT FROM AUTHOR]

The anisotropy of rare earth magnesium (Mg-RE) alloys has attracted significant attention. In this study, the room-temperature compression anisotropy of the extruded Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy was investigated utilizing techniques such as optical microscope (OM), electron backscatter diffraction (EBSD), and viscoplastic self-consistent (VPSC) modeling. The results show that the C0 (with the axis parallel to the extrusion direction) sample exhibited the greatest yield strength of 290 MPa, while the C45 (with the axis inclined at a 45° angle to the extrusion direction) and C90 (with the axis perpendicular to the extrusion direction) samples had yield strengths of 223 MPa and 250 MPa, respectively. The VPSC hardening parameters were significantly adjusted in this study based on the Schmid factor of deformation modes in Mg-RE alloy, particularly increasing the τ0 (Critical Resolved Shear Stress, CRSS) for basal slip. The ratios of CRSS for other deformation modes to basal slip were approximately as follows: CRSSTwin/CRSSBas = 2, CRSSPri/CRSSBas = 2.7 and CRSSPyr/CRSSBas = 3.3, while these ratios in non-rare earth magnesium alloys typically ranged between 0.8 and 3, 5–10 and 8–20. The stress-strain curves and pole figures obtained from the VPSC model exhibited a good agreement with experimental results. Based on the VPSC simulation results, the disparity in the activation level of basal slip was identified as the primary cause of mechanical anisotropy. Twinning only played a significant role in the early phases of deformation, which was not the most primary factor on yield anisotropy.

The high-velocity impact of powder particles in cold-spray additively manufactured (CSAM) parts creates intersplat boundaries with regions of high dislocation densities and sub-grain structures. Upon microstructure and mechanical characterization, CSAM Aluminum 6061 showed non-uniformity with spatial variation in the microstructure and mechanical properties, affecting the overall response of the additively manufactured parts. Post-processing treatments are conducted in as-printed samples to improve particle bonding, relieve residual stresses, and improve mechanical properties. In this work, we attempt to implement the effects of grain size and distribution of smaller grains along the intersplat boundaries using the grain size distribution function and powder size information to accurately predict the deformation response of cold-sprayed material using a mean-field viscoplastic self-consistent (VPSC) model. The incorporation of an intersplat boundary term in the VPSC model resulted in a stress–strain response closely matching the experimental findings, preventing the superficially high stresses observed due to Hall–Petch effects from ultra-fine-grain structures. Likewise, the results from the grain analysis showed the combined effects of grain size, orientation, and intersplat mechanisms that captured the stresses experienced and strain accommodated by individual grains. [ABSTRACT FROM AUTHOR]

The differences in the deformation mechanisms during uniaxial tension of cast and extruded Mg–2Y-0.5Zr (wt%) alloys have been investigated by using EBSD-based slip trace analysis and VPSC simulation methods, and a novel method for counting the activity of slip/twinning using grain area has been proposed. Slip trace analysis reveals that enhanced ductility and reduced tensile-compressive asymmetry observed in the Mg–2Y-0.5Zr (wt%) alloy can be attributed to the addition of the Y element, which modified the texture, and promoted pyramidal slip and suppressed prismatic slip. The extruded alloy exhibits a distinctive pseudo-fiber bimodal microstructure, which contributes to its superior ductility. The VPSC results indicate that the CRSSnon-basal/CRSSbasal ratio of the extruded alloys decreases, whereas the CRSStwinning/CRSSbasal ratio increases, which is attributed to the different effects of the grain refinement on the different deformation modes. In addition, both the VPSC results and the slip trace analysis results indicate that the extruded alloy exhibits reduced non-basal slip activity compared to the cast alloy at similar strain levels. The work-hardening rate curves and VPSC parameters give a reasonable explanation that the key to the increase in the ductility of Mg–Y–Zr alloys after extrusion is the decrease in the basal hardening rate rather than the non-basal slip activity. The refinement of grain size leads to a significant decrease in basal slip hardening rate, primarily due to the decrease in the additional hardening effect caused by tensile twinning and the generation of an additional GBS mechanism in the pseudo fiber microstructure.

Improving both the magnetic properties and strength of non-oriented electrical steel used in driving motors of new energy vehicles is a great challenge. In this study, a 4.5 wt% Si non-oriented electrical steel that had a strong {114} texture and exhibited excellent magnetic and high strength, was produced via hot rolling, cold rolling and annealing. The texture evolution of hot-rolled plate with strong Goss and medium strength λ-fiber ({100}) was investigated in detail during rolling and annealing. The VPSC model was used to simulate the texture evolution during the rolling process, of which the neff model could satisfactorily explain the classical rotation route of Goss and Cube. At the initial stage of recrystallization, the orientation of the recrystallized grains, characterized by electron backscatter diffraction (EBSD), was closely related to the orientation of the hot-rolled plate and rotation path during the rolling process. This clear evidence indicated that the initial recrystallized grains were oriented nucleation. During the recrystallization process, the characterization of specific orientations by quasi-in-situ EBSD revealed that the unusual {114} was formed by an oriented growth mechanism. Texture evolution during the recrystallization indicated oriented nucleation as an inherent property responsible for the initial recrystallization texture, while oriented growth was influenced by deformed grain size and grain boundary characteristics.

Deformation twins act as one of the deformation characteristics of hexagonal close packed (HCP) materials and occur during machining of Ti–6Al–4V alloy. To clarify the hardening mechanisms of deformation twins in Ti–6Al–4V machined surface, work-hardening effects induced by grain refinement in meso scale as well as deformation twins in micro scale were investigated. A 2D cutting finite element (FE) model was established to predict grain refinement in multi-scales and its hardening behavior during machining of Ti–6Al–4V. A visco-plastic self consistent model (VPSC) coupled with predominant twin reorientation (PTR) scheme was also used to simulate stress variation with considering the activations of twin systems. The results show that different grain refinement degrees in meso scale are observed with the increasing of cutting speeds (100–500 m/min). {101¯1} compression nano twins generate at higher cutting speeds, and the twin volume fraction is relatively small (20%). The hardening behaviors of grain refinement in meso scale as well as nano twins predicted with FE model and VPSC model are similar, and the generation of nano twins cause inhomogeneous hardening in Ti–6Al–4V machined surface. Nano-indentation tests further prove the accuracy of the prediction results for the hardening effect induced by nano twins in Ti–6Al–4V machined surface. The results provide two explanations and quantitative evaluations for the hardening effects of deformation twins from the macroscopic stress and the microscopic deformation of slip and twinning modes.

In directional forming processes, such as rolling and extrusion, the grains can develop preferred crystal orientations. These preferred orientations—the texture—are the main cause for material anisotropy. This anisotropy leads to phenomena such as earing, which occur during further forming processes, e.g., during the deep drawing of sheet metal. Considering anisotropic properties in numerical simulations allows us to investigate the effects of texture-dependent defects in forming processes and the development of possible solutions. Purely phenomenological models for modeling anisotropy work by fitting material parameters or applying measured anisotropy properties to all elements of the part, which remain constant over the duration of the simulation. In contrast, crystal plasticity methods, such as the visco-plastic self-consistent (VPSC) model, provide a deeper insight into the development of the material microstructure. By experimentally measuring the initial texture and using it as an initial condition for the simulations, it is possible to predict the evolution of the microstructure and the resulting effect on the mechanical properties during forming operations. The results of the simulations with the VPSC model show a good agreement with corresponding compression tests and the earing phenomenon, which is typical for cup deep drawing.

The high-velocity impact of powder particles in cold-spray additively manufactured (CSAM) parts creates intersplat boundaries with regions of high dislocation densities and sub-grain structures. Upon microstructure and mechanical characterization, CSAM Aluminum 6061 showed non-uniformity with spatial variation in the microstructure and mechanical properties, affecting the overall response of the additively manufactured parts. Post-processing treatments are conducted in as-printed samples to improve particle bonding, relieve residual stresses, and improve mechanical properties. In this work, we attempt to implement the effects of grain size and distribution of smaller grains along the intersplat boundaries using the grain size distribution function and powder size information to accurately predict the deformation response of cold-sprayed material using a mean-field viscoplastic self-consistent (VPSC) model. The incorporation of an intersplat boundary term in the VPSC model resulted in a stress–strain response closely matching the experimental findings, preventing the superficially high stresses observed due to Hall–Petch effects from ultra-fine-grain structures. Likewise, the results from the grain analysis showed the combined effects of grain size, orientation, and intersplat mechanisms that captured the stresses experienced and strain accommodated by individual grains.

The predictions of mechanical responses (stress–strain variations) in the machining of Ti-6Al-4V alloy are important to analyze the deformation conditions of machining to optimize the machining parameters and investigate the generation of a machined surface. The selection of a constitutive model is an essential factor that determines the deformation behavior in the machining simulation model. In this paper, two constitutive models of a modified Johnson–Cook (JC) equation and visco-plastic self-consistent (VPSC) model were used to investigate the stress–strain evolutions in the machining process of Ti-6Al-4V. A finite element (FE) machining model was established, considering the influences of grain refinement and deformation twins, based on a modified JC equation. The VPSC model was fitted based on the macro-strain rate sensitivity of the JC equation. The prediction results of the stress–strain curves of two models were compared, and their validities were further proved. The results show that flow stress hardening and inhomogeneities are caused by multi-scale grain refinement during the machining process of Ti-6Al-4V. Five slip deformation modes and one compressive twinning mode were activated in the VPSC model to be consistent with the macro-deformation behavior predicted with the FE model. The validations show the effectiveness of the modified JC equation, considering microstructural changes and the fitted VPSC model, in predicting dynamic behavior in the machining process of Ti-6Al-4V. The results provide two aspects of macro-deformation and polycrystal plasticity to elucidate the stress variations that occur during the machining of Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

In this study, the microstructure evolution and deformation behavior of the extruded Mg-5Al-0.6Sc (AS51) alloy during tensile testing at room temperature (RT) and 250 °C were investigated by electron backscattered diffraction (EBSD) characterization and Visco Plastic Self Consistent (VPSC) simulation. The results showed that a continuous hardening behavior of the alloy occurred during the deformation at RT, and a certain softening was caused by the occurrence of dynamic recovery (DRV) and dynamic recrystallization (DRX) in the late stage of deformation at 250 °C. The primary deformation mechanism at both RT and 250 °C was dislocation slip, with prismatic slip being the dominant deformation mode, and no significant changes in grain size or texture type occurred. By identifying the activated twin variants, the results indicated that the selection of twin variants was closely related to the local stress concentration. The relatively low activation frequency of extension twinning at 250 °C is partly attributed to the fact that the consumption of dislocations by DRV and DRX can effectively relax the local stress concentration. Meanwhile, the DRX mechanism during the deformation of the alloy at 250 °C was mainly discontinuous dynamic recrystallization (DDRX), with a low recrystallization fraction. [ABSTRACT FROM AUTHOR]

Parsing the effect of slip-twin interactions on the strain rate and thermal sensitivities of Magnesium (Mg) alloys has been a challenging endeavor for scientists preoccupied with the mechanical behavior of hexagonal close-packed alloys, especially those with great latent economic potential such as Mg. One of the main barriers is the travail entailed in fitting the various stress–strain behaviors at different temperatures, strain rates, loading directions applied to different starting textures. Taking on this task for two different Mg alloys presenting different textures and as such various levels of slip-twin interactions were modeled using visco-plastic self-consistent (VPSC) code. A recently developed routine that captures dislocation transmutation by twinning interfaces on strain hardening within the twin lamellae was employed. While the strong texture was exemplified by traditional rolled AZ31 Mg alloys, the weak texture was represented by ZEK100 Mg alloy sheets. The transmutation model incorporated within a dislocation density based hardening model showed enhanced flexibility in predicting the complex strain rate and thermal sensitive behavior of Mg textures' response to various mechanical loading schemes. [ABSTRACT FROM AUTHOR]

The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction (EBSD) measurement and visco-plastic self-consistent (VPSC) modeling. These results show that except basal slip and prismatic slip, {101¯2} extension twin (ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction (RD) of sheet, the activity of {101¯2} ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When {101¯2} ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component (c-axis//ND, normal direction). By comparison, when the role of {101¯2} ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component (c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal slip, the smaller separation is between these two tilted basal poles. Besides, VPSC modeling overestimates volume fractions of {101¯2} ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of {101¯2} ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.

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]

The predictions of mechanical responses (stress–strain variations) in the machining of Ti-6Al-4V alloy are important to analyze the deformation conditions of machining to optimize the machining parameters and investigate the generation of a machined surface. The selection of a constitutive model is an essential factor that determines the deformation behavior in the machining simulation model. In this paper, two constitutive models of a modified Johnson–Cook (JC) equation and visco-plastic self-consistent (VPSC) model were used to investigate the stress–strain evolutions in the machining process of Ti-6Al-4V. A finite element (FE) machining model was established, considering the influences of grain refinement and deformation twins, based on a modified JC equation. The VPSC model was fitted based on the macro-strain rate sensitivity of the JC equation. The prediction results of the stress–strain curves of two models were compared, and their validities were further proved. The results show that flow stress hardening and inhomogeneities are caused by multi-scale grain refinement during the machining process of Ti-6Al-4V. Five slip deformation modes and one compressive twinning mode were activated in the VPSC model to be consistent with the macro-deformation behavior predicted with the FE model. The validations show the effectiveness of the modified JC equation, considering microstructural changes and the fitted VPSC model, in predicting dynamic behavior in the machining process of Ti-6Al-4V. The results provide two aspects of macro-deformation and polycrystal plasticity to elucidate the stress variations that occur during the machining of Ti-6Al-4V.

In this study, the microstructure evolution and deformation behavior of the extruded Mg-5Al-0.6Sc (AS51) alloy during tensile testing at room temperature (RT) and 250 °C were investigated by electron backscattered diffraction (EBSD) characterization and Visco Plastic Self Consistent (VPSC) simulation. The results showed that a continuous hardening behavior of the alloy occurred during the deformation at RT, and a certain softening was caused by the occurrence of dynamic recovery (DRV) and dynamic recrystallization (DRX) in the late stage of deformation at 250 °C. The primary deformation mechanism at both RT and 250 °C was dislocation slip, with prismatic slip being the dominant deformation mode, and no significant changes in grain size or texture type occurred. By identifying the activated twin variants, the results indicated that the selection of twin variants was closely related to the local stress concentration. The relatively low activation frequency of extension twinning at 250 °C is partly attributed to the fact that the consumption of dislocations by DRV and DRX can effectively relax the local stress concentration. Meanwhile, the DRX mechanism during the deformation of the alloy at 250 °C was mainly discontinuous dynamic recrystallization (DDRX), with a low recrystallization fraction.

Magnesium–lithium alloy is the lightest metal alloy material so far, and the ultra-thin plate is also one of the main trends in the future development of Mg-Li alloy. In order to explore how to prepare LZ91 ultra-thin Mg-Li alloy, this topic adopts the combination of the finite element method (FEM) and visco-plastic self-consistent (VPSC) calculation, electron back-scattered diffraction (EBSD) and tensile experiment, and uses the asymmetric warm rolling process to realize the processing of ultra-thin LZ91 Mg-Li alloy plate with a thickness of 0.25 mm. The experimental results show that the maximum basal texture strengths of 1 mm initial plate and 0.25 mm ultra-thin rolled plate are 36.02 mud and 29.19 mud, respectively. The asymmetric warm rolling process not only reduces the basal texture strength but also significantly refines the grains. The tensile strength and yield strength of 0.25 mm ultra-thin rolled plate along the rolling direction reached 206.8 MPa and 138.4 MPa, respectively. This has a positive effect on the mechanical properties of subsequent materials. VPSC results show that the base slip is the main factor in Mg-Li alloy asymmetric warm rolling, and a large number of tensile twinning are initiated due to the coordinated deformation of the body-centered cubic (BCC) phase, which is beneficial to improve the plastic deformation capacity of Mg-Li alloy. [ABSTRACT FROM AUTHOR]

The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction (EBSD) measurement and visco-plastic self-consistent (VPSC) modeling. These results show that except basal slip and prismatic slip, { 10 1 ¯ 2 } extension twin (ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction (RD) of sheet, the activity of { 10 1 ¯ 2 } ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When { 10 1 ¯ 2 } ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component (c -axis//ND, normal direction). By comparison, when the role of { 10 1 ¯ 2 } ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component (c -axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal slip, the smaller separation is between these two tilted basal poles. Besides, VPSC modeling overestimates volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results. [ABSTRACT FROM AUTHOR]

Parsing the effect of slip-twin interactions on the strain rate and thermal sensitivities of Magnesium (Mg) alloys has been a challenging endeavor for scientists preoccupied with the mechanical behavior of hexagonal close-packed alloys, especially those with great latent economic potential such as Mg. One of the main barriers is the travail entailed in fitting the various stress–strain behaviors at different temperatures, strain rates, loading directions applied to different starting textures. Taking on this task for two different Mg alloys presenting different textures and as such various levels of slip-twin interactions were modeled using visco-plastic self-consistent (VPSC) code. A recently developed routine that captures dislocation transmutation by twinning interfaces on strain hardening within the twin lamellae was employed. While the strong texture was exemplified by traditional rolled AZ31 Mg alloys, the weak texture was represented by ZEK100 Mg alloy sheets. The transmutation model incorporated within a dislocation density based hardening model showed enhanced flexibility in predicting the complex strain rate and thermal sensitive behavior of Mg textures’ response to various mechanical loading schemes.

Modeling of metals deforming by twinning requires reorienting the matrix into twin orientation. In twinning models like the Predominant Twin Reorientation scheme (PTR), a threshold volume fraction is defined with an empiric equation to reorient the parent grain into the dominant twin variant. This equation contains two parameters which are first investigated in the present study, showing their effect on simulated flow stress and twin volume fraction evolution. Magnesium, with a tension and a compression twinning modes, is taken as an example to compare the expected experimental behavior and the modeled behavior. Complex deformations such as strain path change and multiple twinning are modeled with the PTR, and simulated stress, twin volume fraction and texture are correlated with the expected behavior. The PTR shows a good agreement with experiments when the twin volume fraction corresponds to the fraction of grains reoriented into twins, but limited predictability when the twinned grains are not reoriented.

The microstructure and texture of different rolling processes in situ Cu–15Cr sheets are studied. The results show that the second phase Cr in the material gradually become broken, flattened, merged and homogenized from dendritic state to oriented thin lath. Meanwhile, the texture in distributed copper matrix grains finally forms Brass {110}<112>, Goss {001}<110> and Copper {112}<111> textures along with Cr phase texture of randomly distributed α-fiber (<110> fiber) and γ-fiber (<111> fiber) texture. Based on VPSC (visco-plastic self-consistent model), the texture of cold rolled Cu–15Cr composite is simulated, and the simulation result indicates that obvious twinning effect in the copper matrix appears with a feature of a special texture evolution law of Goss. [ABSTRACT FROM AUTHOR]

Featured Application: We study the mechanical deformation and formability of multi-phase high-strength steels in basis to microstructural data. This work presents an advanced crystal plasticity model for the simulation of the mechanical behavior of multiphase advanced high-strength steels. The model is based on the Visco-Plastic Self-Consistent (VPSC) model and uses information about the material's crystallographic texture and grain morphology together with a grain constitutive law. The law used here, based on the work of Pantleon, considers how dislocations are created and annihilated, as well as how they interact with obstacles such as grain boundaries and inclusions (carbides). Additionally, strain rate sensitivity is implemented using a phenomenological expression derived from literature data that does not require any fitting parameter. The model is applied to the study of two bainitic steels obtained by applying different heat treatments. After fitting the required parameters using tensile experiments in different directions at quasi-static and high strain rates, formability properties are determined using the model for the performance of virtual experiments: uniaxial tests are used to determine r-values and stress levels and biaxial tests are used for the calculation of yield surfaces and forming limit curves. [ABSTRACT FROM AUTHOR]

Microstructure and texture evolution of β-quenched Zr-xNb-0.4Mo (x = 0, 0.4, 0.6 and 1.0 wt %) alloys during the cold rolling process were systematically investigated. The Zr-xNb-0.4Mo alloys exhibit the area fractions of the martensitic structure are 33.2%, 69.4%, 100% and 100% with an increase in Nb content. Under the same rolling gap (1.2 mm), the rolling reductions are 24%, 28%, 29.7% and 30%, respectively. To understand the reason for the gradual increase of rolling reductions until approximately 30%, a visco-plastic self-consistent (VPSC) model was employed to predict the texture evolution and relative activity of different deformation modes. The variation of average Schmid factors (SFs) and the variation of the relative activity of different deformation modes before and after cold rolling were calculated and compared. With the increase of Nb content, a similar variation law between the variation of average SF and the variation of relative activity was found. The basal slip in Zr-0.4Nb-0.4Mo alloy is difficult to activate due to the initial texture of Zr-0.4Nb-0.4Mo alloy. Pyramid slip can accommodate the strain along the normal direction (ND), which is beneficial to the high plasticity of Zr alloys during cold rolling. By comparing the variation of average SF of pyramid slip, it is found that the larger rolling reductions of Zr-0.6Nb-0.4Mo alloy and Zr-1.0Nb-0.4Mo alloys can be attributed to the activation of pyramid slip. The existence of primary α grains can decrease the average SF and inhibit the activation of pyramid slip. The cold rolling can make the martensite plates crushed and refined, but not to the primary α grains. [Display omitted] • The texture evolution of β-quenched Zr-xNb-0.4Mo alloys under rolling is studied. • The smaller rolling reductions can be attributed to the existence of primary α grains. • The primary α grains decrease the average SF of pyramid slip. • The primary α grain can restrict the activation of pyramid slip. • The cold rolling can make martensite plates crushed and refined, but not to primary α grains. [ABSTRACT FROM AUTHOR]

In the present investigation in-plane anisotropy in tensile and ratcheting behavior of cold rolled and annealed commercially pure titanium plate has been studied. Flat tensile and fatigue test specimen oriented at 0, 45, and 90 degree to the rolling direction from the rolling directiontransverse direction (RDTD) plane of the plate has been machined out. Specimens with loading axis at 0, 45 and 90 degree to RD have been designated as 0T, 45T and 90T for tensile and 0R, 45R and 90R for fatigue. Owing to initial TD split basal texture of as received plate, 0T sample has crystallographic direction aligned with loading axis. It shows lowest yield strength but highest ductility in monotonic tension. Although ultimate tensile strength (UTS) and strain to failure of samples 45T and 90T are similar, the former has significantly lower yield strength than the latter, indicating different strain-hardening behavior due to different slip/twin activity. On the other hand, 0R sample exhibits longer ratcheting life while 90R sample accumulates highest ratcheting strain. This has been attributed to the formation of intersecting multi-variant twins, which increases fatigue crack propagation resistance during cyclic deformation of 0R sample. Viscoplastic self-consistent (VPSC) simulations of one-cycle tension-compression-reload tension indicate alternating activity of pyramidal c+a slip and extension twinning with loading cycle. The detwinning of extension twin during compression cycle induces cross slip activity, which causes rapid accumulation of strain leading to early fatigue failure of 45R and 90R sample.

Magnesium–lithium alloy is the lightest metal alloy material so far, and the ultra-thin plate is also one of the main trends in the future development of Mg-Li alloy. In order to explore how to prepare LZ91 ultra-thin Mg-Li alloy, this topic adopts the combination of the finite element method (FEM) and visco-plastic self-consistent (VPSC) calculation, electron back-scattered diffraction (EBSD) and tensile experiment, and uses the asymmetric warm rolling process to realize the processing of ultra-thin LZ91 Mg-Li alloy plate with a thickness of 0.25 mm. The experimental results show that the maximum basal texture strengths of 1 mm initial plate and 0.25 mm ultra-thin rolled plate are 36.02 mud and 29.19 mud, respectively. The asymmetric warm rolling process not only reduces the basal texture strength but also significantly refines the grains. The tensile strength and yield strength of 0.25 mm ultra-thin rolled plate along the rolling direction reached 206.8 MPa and 138.4 MPa, respectively. This has a positive effect on the mechanical properties of subsequent materials. VPSC results show that the base slip is the main factor in Mg-Li alloy asymmetric warm rolling, and a large number of tensile twinning are initiated due to the coordinated deformation of the body-centered cubic (BCC) phase, which is beneficial to improve the plastic deformation capacity of Mg-Li alloy.

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]

Quartz c‐axis fabrics in natural mylonites can vary to such an extent that they apparently give opposite senses of shear in a single thin section. Many hypotheses have been invoked to explain this. Here, we couple our self‐consistent multiscale approach for flow partitioning with the viscoplastic self‐consistent model for c‐axis fabric simulation to investigate quartz c‐axis fabric development. Quartz aggregates are regarded as microscale Eshelby inhomogeneities embedded in a macroscale medium whose effective rheology is represented by a hypothetical homogeneous equivalent medium which is assumed to be rheologically isotropic or has a planar anisotropy. We reproduced the observed quartz c‐axis fabrics. We found that although the microscale flow fields are distinct from one another and from the macroscale flow, the microscale vorticity in every inhomogeneity has the same sense as the macroscale vorticity. This implies that one can use the average of the microscale vorticity axes determined through the crystallographic vorticity axis analysis to obtain the macroscale vorticity axis. However, quartz c‐axis fabrics cannot be used to determine the vorticity number where flow partitioning is significant. Key Points: Multiscale simulation of quartz c‐axis fabrics coupling Multi order power law approach and visco‐plastic self‐consistent modelingObserved natural and experimental quartz c‐axis fabric variations explained by flow partitioningNatural quartz c‐axis fabric variation reflected macroscale finite strain gradients without sense of vorticity reversal [ABSTRACT FROM AUTHOR]

With the advent of integrated computational materials engineering, there is a drive to exchange statistical confidence in a design obtained from repeated experimentation with one developed through modeling and simulation. Since these models are often missing physics or include incomplete knowledge or simplifying assumptions into their mathematical construct, they may not capture the physical system or process adequately over the entire domain. This can lead to a systematic discrepancy, otherwise known as model misfit, between the model output and the system it represents over at least part of the domain. However, by accounting for this discrepancy in uncertainty analyses, reliable inference, and prediction on the model parameters and material behavior can be made despite the missing physics. The previous statement is contingent on two conditions: (1) the discrepancy is systematic, and (2) the structure of the discrepancy is well understood, which is required to minimize issues with non-identifiability among unknown model components. We illustrate these insights via a case study of inference and prediction in a phenomenological meso-scale VPSC crystal plasticity model, which does not contain physics describing the elastic regime of deformation. Inference is performed via a Bayesian approach enabled by posterior simulation. Posterior uncertainty about unknown model parameters takes into account observation error, uncertainty stemming from aleatoric sample-to-sample variability, and model form error. Posterior uncertainty in the unknown Voce hardening parameters is propagated to generate a distribution of the stress–strain response in both the elastic and plastic regimes. Additionally, posterior predictive distributions are simulated to establish uncertainty bounds for future unobserved data. [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]

This work presents an advanced crystal plasticity model for the simulation of the mechanical behavior of multiphase advanced high-strength steels. The model is based on the Visco-Plastic Self-Consistent (VPSC) model and uses information about the material’s crystallographic texture and grain morphology together with a grain constitutive law. The law used here, based on the work of Pantleon, considers how dislocations are created and annihilated, as well as how they interact with obstacles such as grain boundaries and inclusions (carbides). Additionally, strain rate sensitivity is implemented using a phenomenological expression derived from literature data that does not require any fitting parameter. The model is applied to the study of two bainitic steels obtained by applying different heat treatments. After fitting the required parameters using tensile experiments in different directions at quasi-static and high strain rates, formability properties are determined using the model for the performance of virtual experiments: uniaxial tests are used to determine r-values and stress levels and biaxial tests are used for the calculation of yield surfaces and forming limit curves.

Integrated Computational Materials Engineering (ICME) is an engineering approach where the materials, manufacturing process, and component designs are optimized concurrently before an actual physical component is realized. This requires the integration of models across vast length and timescales. A key benefit of ICME is the ability to reduce the bulk of expensive and lengthy experiments via tailored simulation. However, ICME introduces new challenges and limitations as the statistical confidence in the final design and manufacturing process must be established from simulation rather than experimental observation and testing. The computational materials science community has not formally adopted tools for verification and validation or UQ for materials simulations. In this study, a Bayesian hierarchical model is considered which accounts for parameter uncertainty, the inherent variability in the properties of material samples tested, and measurement noise. The Bayesian inferential framework is used to calibrate model parameters given calibration data and also to make forward predictions with a confidence level established through the highest posterior density intervals. The generality of the framework is demonstrated through two case studies: (1) parameter estimation for a crystal plasticity model which provides key microstructural and grain-level deformation information to use within the ICME chain; (2) the estimation in uncertainty in thermodynamic phase stability from multiple databases for phase stability. [ABSTRACT FROM AUTHOR]

Increasing the plastic deformation temperature of Mg alloys results in higher strain rate sensitivity, easier activation of secondary slip modes, and impeded twinning. In this study, the strain rate sensitivity is estimated for each deformation mode, and visco-plastic self-consistent modeling is used to reproduce the plastic deformation behavior of an Mg-3Al-1Zn O-temper plate from 150 to 450°C. Twinning and basal slip have relatively low strain rate sensitivity, whereas secondary slip modes are highly strain rate sensitive at high temperature. The texture evolution and plastic anisotropy are modeled at different temperatures and strain rates. Results show that when the strain rate sensitivity is taken into account, compared with rate independent critical resolved shear stresses, the material parameters and predictions are different. In particular, this study shows that, for hot deformation, there is a critical strain rate above which secondary slip modes predominate, and beyond which tension twinning is activated. A similar transition is expected for modes that have different strain rate sensitivity. [ABSTRACT FROM AUTHOR]

The impact of twin transmission between neighboring grains as a contributor to overall twin activity is considered via a neighborhood viscoplastic self-consistent (NVPSC) model. The NVPSC model is an extension of a stochastic model for twin nucleation developed by Niezgoda et al. and a dislocation density based hardening law model developed by Knezevic et al. Beyond the baseline combined framework, the new model tracks sets of neighboring grains and allows twin transmission between them under certain conditions. The influence of grain boundary (GB) character is included in the stochastic models of twin nucleation and transmission. The starting texture from a rolled magnesium alloy AZ31B sheet was obtained using electron backscatter diffraction (EBSD) for initial input into the NVPSC. The sample was further deformed by uniaxial compression to encourage twin formation and the corresponding texture information was collected using EBSD. The accuracy of simulated twin activity was determined by comparing it with the twin activity seen in the deformed sample. The total number of predicted twins and the number of transmission twins is found to agree favorably with those observed via the EBSD scans. This validation demonstrates the significance of incorporating twin transmission as a twin formation mode in predictive models for this material. • A neighborhood visco plastic self-consistent (NVPSC) model with twin transmission is presented. • The simulated results are compared to the in situ experimental results for magnesium alloy AZ31B. • The simulated results provided by the NVPSC model is in better agreement with experimental results. • As reported in previous works, low angle grain boundaries are more likely to promote twin transmission. [ABSTRACT FROM AUTHOR]

In the present work, deformation mechanism in single-point incremental forming (SPIF) of drawing quality steel with a fully ferritic microstructure was studied. The effect of tool diameter and vertical step size on the micromechanisms of plastic deformation in SPIF was investigated by observing changes in microstructure and lattice rotation. It was observed that the fraction of grains with {111} ‖ normal direction (ND), which constitutes the gamma fiber in BCC materials, decreased with decrease in tool diameter and vertical step size. It is known that the state of deformation in SPIF is near to plane strain with the direction of major strain being always perpendicular to tool travel direction and negligible strain parallel to tool movement direction. Microstructural evidence for this observation and also for the presence of through thickness shear (TTS) components at smaller step size and tool diameter was observed. Viscoplastic self-consistent (VPSC) simulations revealed that the activity of 112 < 11 1 ¯ > slip system decreased in comparison to 110 < 1 1 ¯ 1 > slip system in the presence of TTS which manifested as the deviation from {111} ‖ ND position at smaller step size and tool diameter. [ABSTRACT FROM AUTHOR]

In the present investigation in-plane anisotropy in tensile and ratcheting behavior of cold rolled and annealed commercially pure titanium plate has been studied. Flat tensile and fatigue test specimen oriented at 0, 45, and 90 degree to the rolling direction from the rolling direction-transverse direction (RD-TD) plane of the plate has been machined out. Specimens with loading axis at 0, 45 and 90 degree to RD have been designated as 0T, 45T and 90T for tensile and 0R, 45R and 90R for fatigue. Owing to initial TD split basal texture of as received plate, 0T sample has crystallographic direction {1010} -{1120} aligned with loading axis. It shows lowest yield strength but highest ductility in monotonic tension. Although ultimate tensile strength (UTS) and strain to failure of samples 45T and 90T are similar, the former has significantly lower yield strength than the latter, indicating different strainhardening behavior due to different slip/twin activity. On the other hand, 0R sample exhibits longer ratcheting life while 90R sample accumulates highest ratcheting strain. This has been attributed to the formation of intersecting multi-variant twins, which increases fatigue crack propagation resistance during cyclic deformation of 0R sample. Viscoplastic self-consistent (VPSC) simulations of one-cycle tension-compression-reload tension indicate alternating activity of pyramidal slip and extension twinning with loading cycle. The detwinning of extension twin during compression cycle induces cross slip activity, which causes rapid accumulation of strain leading to early fatigue failure of 45R and 90R sample. [ABSTRACT FROM AUTHOR]

Abstract Crystallographic preferred orientations (CPOs) in olivine are widely used to infer the mechanisms, conditions, and kinematics of deformation of mantle rocks. Recent experiments on water-saturated olivine were the first to produce a complex CPO characterised by bimodal orientation distributions of both [100] and [001] axes and inferred to form by combined activity of (001)[100], (100)[001], and (010)[100] slip. This result potentially provides a new microstructural indicator of deformation in the presence of elevated concentrations of intracrystalline hydrous point defects and has implications for the interpretation of seismic anisotropy. Here, we document a previously unexplained natural example of this CPO type in a xenolith from Lesotho and demonstrate that it too may be explained by elevated concentrations of hydrous point defects. We test and confirm the hypothesis that combined (001)[100], (100)[001], and (010)[100] slip were responsible for formation of this CPO by (1) using high-angular resolution electron backscatter diffraction to precisely characterise the dislocation types present in both the experimental and natural samples and (2) employing visco-plastic self-consistent simulations of CPO evolution to assess the ability of these slip systems to generate the observed CPO. Finally, we utilise calculations based on effective-medium theory to predict the anisotropy of seismic wave velocities arising from the CPO of the xenolith. Maxima in S-wave velocities and anisotropy are parallel to both the shear direction and shear plane normal, whereas maxima in P-wave velocities are oblique to both, adding complexity to interpretation of deformation kinematics from seismic anisotropy. Highlights • Unusual bimodal CPO of olivine in experiments and nature explained. • HR-EBSD and VPSC constrain dislocation types and activity in hydrous and anhydrous olivine. • Intracrystalline hydrous point defects increase slip on (001)[100] and (100)[001]. • Complex relationship between seismic properties and deformation kinematics. [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.

Crystal plasticity models attempt to reproduce the complex deformation processes of polycrystalline metals based on a virtual representation of the real microstructure. When choosing this representation, a compromise must be made between level of detail at the local level and statistical significance of the aggregate properties, also taking into account the computational cost of each solution. In this work, the correlation between crystallographic orientation and grain size is considered in the definition of virtual microstructures for the simulation of the mechanical behavior of AISI 420 stainless steel (consisting of a ferrite matrix with large carbide precipitates), in order to improve the accuracy of the solution without increasing model complexity or computation time. Both full-field (DAMASK) and mean-field models (Visco Plastic Self Consistent (VPSC)) are used together in combination with experimental results to study the validity of the assumptions done in each of the models.

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 The effect of mechanical twinning and ε-martensite formation on the formability of austenitic alloys in complex strain pathways has been examined. One of the alloys studied deformed by deformation twinning and slip (TWIP), and this alloy was examined with two grain sizes. The second alloy showed three concurrent deformation modes (slip, TWIP and ε-martensite TRIP). The TWIP/TRIP alloy showed a markedly reduced formability compared to similar alloys, and this has been attributed to a combination of the early development of strain localizations, and the stress-induced formation of ε-martensite. It is suggested that the TRIP effect may not be desirable in high formability sheet steels if the transformation product is ε-martensite. Microstructural examination revealed that the different strain paths develop different twin volume fractions. Plasticity modelling has shown this to be the result of differences in texture development in the different strain paths. In microstructures where slip, TWIP and TRIP can operate concurrently, the stress to activate twinning is unaffected by the additional deformation mode becoming operative. Graphical Abstract Unlabelled Image Highlights • The formation of ε-martensite in TRIP steel reduces formability. • In austenitic alloys, stress induced transformation in addition to twinning and slip does not affect the twinning behaviour. • The volume fraction of twins exhibits variation depending on the strain pathway due to differences in texture development. [ABSTRACT FROM AUTHOR]

Characteristic textures of cold-rolled low carbon steel consist of the RD// 〈 110 〉 fiber ( α fiber) and ND// ⟨ 111 ⟩ fiber ( γ fiber). Although the development of the γ fiber has been successfully modeled by the relaxed constraints polycrystal plasticity model, modeling of the α fiber has been less successful. In this work, we investigate mechanisms underlying the development of a strong α fiber in a low carbon steel during cold rolling to large thickness reductions of 90%, 98%, and 99.8%. We compare the deformation textures measured using X-ray and electron backscatter diffraction methods with those simulated using polycrystal models, employing one of four homogenization schemes: the Taylor model, Secant model, Tangent model and an intermediate stiffness model between the Secant and Tangent models. The measured textures consist of an extremely strong α fiber and unusually weak γ fiber. The calculated textures achieve the best agreement with the measured ones when (1) the intermediate stiffness model is used to account for grain shape effects, (2) the flow rule exponent ( n ) is chosen to allow for multiple slip in grains, (3) latent hardening effects are suppressed, (4) ⟨ 111 ⟩ slip on { 110 } , { 112 } and { 123 } planes is made available for deformation, and (5) the grains shape is permitted to evolve individually. Taken together, these aspects represent indirectly the effects of cross slip on slip activity, suggesting that the strong α fiber in severely cold rolled steel results from cross slip. Although the cross slip is a well accepted mechanism in b.c.c. crystals, its connection to α fiber dominance in texture development during severe rolling deformation has not been established before. [ABSTRACT FROM AUTHOR]

Electron back-scattering diffraction was used to track the microstructure evolution of a fully annealed Fe-24Mn-3Al-2Si-1Ni-0.06C TWinning Induced Plasticity (TWIP) steel during interrupted reverse (tension-compression) loading. Direct observation of the same selected area revealed that all deformation twins formed during forward tension loading (0.128 true strain) were removed upon subsequent reverse compression loading (0.031 true strain). Consequently, the present study provides the first unambiguous experimental evidence of de-twinning during the reverse loading of a polycrystalline TWIP steel. The reverse loading behaviour was simulated by a dislocation-based hardening model embedded in the Visco-Plastic Self-Consistent (VPSC) polycrystal framework taking into account the accumulation and annihilation of dislocations and back-stress effects. The model has been extended to account for the processes of twinning and de-twinning, as well as the twin barrier effect under load reversal. A new formulation based on the changes in the dislocation mean free path is proposed to track twin lamellae generation/annihilation throughout deformation along with its associated effect on hardening. [ABSTRACT FROM AUTHOR]

The effects of grain refinement on the quasi-static compressive behavior of AISI 321 austenitic stainless steel (ASS) were studied. The effect of strain on the final microstructure after compressive deformation was also investigated. The compression tests on steel specimens were conducted at a strain rate of 4.2 × 10 −3 s −1 . Ultrafine-grained (UFG) specimen with the grain size of 0.24 μm exhibits an excellent combination of high yield strength (∼1 GPa) and good strain hardenability. Meanwhile, the coarse-grained (CG) specimen with the grain size of 37 μm exhibits yield strength of ∼0.2 GPa. At 0.53 true strain, UFG and CG specimens exhibit compressive strengths of 5.95 and 4.80 GPa, respectively. The Hall-Petch relation constants, σ o , and K, for the AISI 321 ASS were estimated to be 128 MPa and 478 MPa μm −0.5 , respectively. The strain hardening behavior of both UFG and CG specimens occur in three distinctive stages. CG specimen exhibits higher strain hardening rate than the UFG specimen up to a critical true strain of 0.4, above which strain hardening rate in UFG becomes greater. X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) techniques were used for microstructural analyses to understand the underlying mechanisms behind the strain hardening behavior. Texture evolution during deformation, orientation relationship between phases and the sequence of martensitic phase transformation were also studied and are discussed in this paper. Visco-plastic self-consistent (VPSC) modeling was employed to decipher the role of deformation mechanisms in macroscopic stress-strain response and also in texture evolution during uniaxial compression loading. [ABSTRACT FROM AUTHOR]