The Swift effect, namely the axial response accompanying torsion, is strongly affected by twinning mechanisms in magnesium alloys, yet detwinning occurs during torsion, and its quantitative connection to the axial response remains insufficiently clarified. In this work, an extruded AZ31 Mg alloy bar is studied under a pre-compression-free-end torsion loading path to tailor various initial {10–12} extension twin fractions. A continuous transition of the Swift effect from axial contraction to axial elongation is observed with increasing pre-strain, indicating the evolutionary change in the dominant twinning-related contribution to the axial response. Moreover, the elastic visco-plastic self-consistent model with twinning and detwinning scheme, together with torsion-specific finite-element approach (TFE-EVPSC-TDT) reproduces the first-order shear response and captures the overall evolution trend of the second-order axial strain. A novel criterion based on the modified global Schmid factor (GSF) for twinning and detwinning under torsion is proposed: the nucleation and growth of {10–12} extension twin occur in grains or twin structures with a positive GSF, while detwinning is favored in prefabricated twins with a negative GSF, and the orientations of pre-twins may promote either re-twinning or detwinning depending on the orientations of the parent grains. In addition, an analytical “twinning-only” upper-bound model is established to quantify the axial contribution of extension twinning under torsion. The analysis indicates that the maximum twinning-related axial contribution reaches ∼6.66%, and the remaining deviation of the measured axial strain can be attributed to the additional slip-assisted axial extension that becomes increasingly important as shear straining. The findings in the present work provide a new and significant understanding of the twinning and detwinning mechanism in the Swift effect of Mg alloys.

This study systematically investigates the anisotropic deformation mechanisms of AZ31B magnesium alloy under torsional and torsion–axial coupled loadings, aiming to clarify the mechanisms of shear-dominated multiaxial deformation. Through integrated experiments and numerical simulations, we examine torsional characteristics and torsion-tension/compression coupling effects in AZ31 Mg alloy specimens with varied initial textures. Experiments included free-end torsion and coupled torsion-tension tests, while simulations employed an elastic-viscoplastic self-consistent (EVPSC) model incorporating twinning-detwinning (TDT) mechanisms and a torsion-specific finite element (TFE) methodology. The model accurately reproduces: (1) Highly anisotropic, texture-dependent torsional responses; (2) Complex coupling behaviors under combined loading; (3) Constitutive model-sensitive Swift effects. Mechanistic insights were enhanced by analyzing stress/strain distributions, twin volume fraction (TVF) evolution, deformation mechanism activation, and texture development. These findings bridge the knowledge gap between homogeneous and inhomogeneous deformation in Mg alloys and offer guidance for tailoring twinning activity to enhance formability under complex loading.

The behavior of glassy polymers, which is characterized by temperature-, rate-, time-, and stress-state dependence, remains to be fully elucidated. Existing constitutive theories have modelled this phenomenon with varying degrees of success. To date, no universally accepted theory fully and accurately describes the coupled thermo-mechanical response of glassy polymers over a wide temperature range, encompassing low to high strain rates, various time scales, including transient and long-term processes, and arbitrary deformation levels. To address these requirements, a fully thermodynamically coupled constitutive theory is formulated within a comprehensive kinematic and thermodynamic framework. To analyze the macroscopic behavior, three distinct microscopic entanglement structures are introduced into glassy polymers: transient entanglements, slidable entanglements, and permanent entanglements. The effects of external stimuli on the synergy, structural stability, and evolution of these entanglements are investigated, facilitating further elucidation of their disparate roles in regulating the profoundly intricate nonlinear macroscopic properties. By comparing the simulations with the macroscopic features of polycarbonate (PC) and polymethyl methacrylate (PMMA) under different external environments and various stress states, it not only verifies the effectiveness of the new theory in predicting the thermodynamically coupled under different temperatures and deformation rates, but also highlights its comprehensiveness and accuracy in describing time-related behaviors such as creep, stress relaxation, strain recovery, and highly nonlinear under arbitrary deformation

To achieve a strength-ductility synergy in extruded ZM6 magnesium alloy, three torsion-dominated heterogeneous plastic deformation processes were proposed. The deformation mechanisms and the evolution of microstructure, texture, twin volume fraction (TVF), and tensile properties were systematically investigated. The results show that free-end torsion and coupled torsion-tension/compression generate centimeter-scale gradient twin structures across the entire specimen diameter (similar to 10 mm) and positive gradient geometrically necessary dislocation (GND) energy density from the interior to the exterior of the material. In contrast, coupled torsion-compression produces an overall negative gradient twin structure. All three heterogeneous deformation modes effectively overcome the conventional strength-ductility trade-off, leading to simultaneous improvements in strength and ductility. The enhanced mechanical properties mainly originate from the gradient twin structures, dislocation accumulation, and texture evolution induced by heterogeneous deformation. Furthermore, by adjusting the axial loading mode, deformation magnitude, and loading rate, the gradient twin structure and dislocation density can be effectively tailored. These results demonstrate that torsion-dominated heterogeneous deformation provides an effective strategy for tuning the mechanical properties of magnesium alloys.

The Swift effect, namely the axial response accompanying torsion, is strongly affected by twinning mechanisms in magnesium alloys, yet detwinning occurs during torsion, and its quantitative connection to the axial response remains insufficiently clarified. In this work, an extruded AZ31 Mg alloy bar is studied under a pre-compression-free-end torsion loading path to tailor various initial {10u201312} extension twin fractions. A continuous transition of the Swift effect from axial contraction to axial elongation is observed with increasing pre-strain, indicating the evolutionary change in the dominant twinning-related contribution to the axial response. Moreover, the elastic visco-plastic self-consistent model with twinning and detwinning scheme, together with torsion-specific finite-element approach (TFE-EVPSC-TDT) reproduces the first-order shear response and captures the overall evolution trend of the second-order axial strain. A novel criterion based on the modified global Schmid factor (GSF) for twinning and detwinning under torsion is proposed: the nucleation and growth of {10u201312} extension twin occur in grains or twin structures with a positive GSF, while detwinning is favored in prefabricated twins with a negative GSF, and the orientations of pre-twins may promote either re-twinning or detwinning depending on the orientations of the parent grains. In addition, an analytical u201Ctwinning-onlyu201D upper-bound model is established to quantify the axial contribution of extension twinning under torsion. The analysis indicates that the maximum twinning-related axial contribution reaches ~6.66%, and the remaining deviation of the measured axial strain can be attributed to the additional slip-assisted axial extension that becomes increasingly important as shear straining. The findings in the present work provide a new and significant understanding of the twinning and detwinning mechanism in the Swift effect of Mg alloys.

Multiscale simulation plays a pivotal role in macroscopic behavior analysis by incorporating micro-level physical deformation evolutions, which provides valuable insights for materials science and industrial manufacturing. However, its development has remained relatively retarded despite the long-established concept due to the challenge of balancing efficiency and accuracy. To address this issue, the current study introduces a recurrent neural network-based constitutive model as the mesoscale surrogate for crystal plasticity, termed Polycrystalline Linearized Minimal State Cells (PolyLMSC), which comprises two parallel LMSCs to predict both the mechanical response and texture evolution simultaneously. A new texture-mechanics linkage method is proposed based on the Fourier coefficients of generalized spherical harmonic (GSH) functions, where the linearity of Fourier space promotes the PolyLMSC model to extend to different textures. To enhance generalizability across arbitrary loading conditions, arbitrary strain paths with random and diverse variations in incremental size and loading direction are adopted for data generation. During the validation at the single material point, the PolyLMSC model shows good generalization performance across different textures under arbitrary loading. Furthermore, the PolyLMSC model is evaluated through various component-scale simulation cases, illustrating reasonable accuracy at meso- and macroscale predictions with 1 similar to 2 orders of magnitude improvement in computational efficiency compared to conventional crystal plasticity models. The validation results demonstrate the proposed model as a promising candidate for efficient and accurate multiscale simulations, bridging the meso- to macroscales.

The potential of magnesium alloys as lightweight structural materials has caught widespread attention owing to their exceptional balance of low density and mechanical strength. However, the process of producing high-strength magnesium alloys remains challenging. Pre-shearing, which induces a twinned microstructure, can alter the deformation characteristics of magnesium alloys and enhance their mechanical properties. This work investigates the influence of pre-shearing on subsequent tensile behavior of magnesium alloys, with a particular focus on yield strength enhancement. Building on experimental investigations conducted on AZ31 Mg alloy plates, a combined twinning–detwinning (TDT) framework and the elastic viscoplastic self-consistent (EVPSC) model are employed to model the subsequent tension along the different loading directions for the pre-sheared AZ31 plate with different textures. Our study reveals that the amount of pre-shearing has different effects on mechanical behaviors and yield strength enhancement for three initial textures. By adjusting the combinations of loading directions, initial textures, and the amounts of pre-shear strain with or without annealing, we can achieve various levels of yield strength enhancement. Additionally, the significant enhancement of yield strength for the pre-sheared material under subsequent tension along the 45 deg makes the pre-shearing a feasible method to optimize the wrought Mg alloy properties.

The extensive emergence and frequent interaction of shear bands play a pivotal role in the behavior of ductile polymers under large deformations. This paper employs the finite element method to analyze the emergence and evolution of shear bands in polymer tubes under internal pressure. Assuming the tube is sufficiently long, plane strain conditions prevail in the axial direction. The behavior of polymers is represented by the classical elastic-viscoplastic constitutive model, which incorporates influences of pressure, strain rate and temperature on yielding and encompasses intrinsic softening and consequent orientation hardening. Simulations indicate that shear bands initially propagate in a spiral pattern, followed by widening, multiplication, and annihilation indications. These phenomena collectively contribute to the onset and expansion of necks. The competition between the propagation and multiplication of shear bands governs the unpredictability in the initiation sites of necking. Particular attention is paid to four interesting interactions between shear bands (i.e., “detour”, bifurcation, obstruction, “repulsion”) and their genesis mechanisms. The effects of material parameters, initial geometric imperfections, specimen thickness and loading method are systematically discussed. It is demonstrated that intrinsic softening facilitates the emergence and propagation of bands, while orientation hardening contributes to the widening of bands and the expansion of necks. The synergistic effect of intrinsic softening and orientational hardening modulates shear bands’ morphology, multiplication, competition and interaction. The initial imperfection wave number significantly affects the number of shear bands. Periodic symmetric imperfections result in a comparable number of clockwise and counterclockwise shear bands, followed by necks propagating bi-directionally along the specimen. Conversely, periodic asymmetric imperfections induce a unidirectional spiral configuration of shear bands, followed by necks propagating unidirectionally along the specimen. Compared with experiments, it is demonstrated that the constitutive model can qualitatively depict the onset and propagation of necks. The multiplication, bifurcation, “detour”, and obstruction of shear bands frequently observed in experiments can also be predicted well qualitatively.

In the past few years, data-driven models based on artificial neural network (ANN) have been successfully developed and applied to investigate the macro- and micro-mechanical behaviors of various materials. However, these data-driven models are either too complex in structure or lack interpretable physical insights. In the present work, a crystal plasticity-informed data-driven (CPIDD) model is proposed, which updates the microstructural information and parameters associated with the macroscopic constitutive model using a parallel ANN structure, and combines conventional constitutive equations to obtain the stress-strain response, ensuring efficient and stable calculations. In conjunction with the finite element (FE) method, the FE-CPIDD model simulates the micro- and macro-mechanical behaviors of magnesium (Mg) alloys under uniaxial loading, non-proportional loading, four-point bending and unloading. The comparison between the simulations and available experiments (or crystal plasticity simulations) demonstrates the accuracy and effectiveness of the proposed CPIDD model. Using Mg alloys as a representative case, the CPIDD model provides an operational and extensional tool for the design, fabrication, manufacturing, and service of the metallic components.

Hetero-deformation induced (HDI) stress is crucial for the strengthening of heterostructured materials (HSMs), making its quantification essential for understanding the heterogeneous deformation mechanisms. We propose a novel method for measuring HDI stress based on plastic dissipation in hysteresis loops, offering superior accuracy and stability over previous methods, as demonstrated in studies on lamellar materials through experiments and FEM simulations. This approach advances a more objective, microstructure-based understanding of HDI stress in HSMs.

Although variant selection during the phase transformation of zirconium (Zr) alloys has been studied extensively, studies on the formation mechanism of microstructural characteristics related to alpha variant selection remain limited. The formation mechanisms of the self-accommodation morphology and inter-variant boundary characteristics of alpha variants in homogenized Zr-2.5Nb alloy cooled by water quenching (WQ), furnace cooling (FC), and air cooling (AC) were systematically investigated from the perspective of local strain during phase transformation. The alpha variants exhibited triangular morphologies in both the WQ and AC samples, and a colony morphology in the FC sample. Further, there were five types of inter-variant boundaries: Type I <0 0 0 1>/10.53 degrees, Type II <1 1 <(2)over bar> 0>/60 degrees, Type III <<(1.377)over bar> (1) over bar 2.3770.359>/60.83 degrees, Type IV <<(10)over bar> 5 5 (3) over bar>/63.26 degrees, and Type V <1 <(2.38)over bar> 1.380>/90 degrees. The proportion of Type II is up to 98 % in the AC sample and 57.9 % in the WQ sample; the Type I was very low in all three samples; and a high proportion of the Type V was observed in the FC sample (23.6 %). The self-accommodation morphology of alpha variants is closely related to the equivalent strain (epsilon(VM)) during the variant selection. Theoretical calculations indicated that, for a specific 2-variant combinations, there were always one or more 3-variant combinations with a lower epsilon(VM) than the 2-variant combinations. A lower epsilon(VM) contributes to the presence of 3-variant combinations, which forms a triangle morphology. The formation of inter-variant boundaries is determined by the type and frequency of variants as well as the epsilon(VM) of the 2-variant combinations. The order of the mean values of epsilon(VM) for the five types of boundaries was Type II (0.0757), Type III (0.0859), Type IV (0.1012), Type V (0.1112), and Type I (0.1307). That is, Type II is the easiest and Type I is the most difficult, which resulted in a very high fraction of Type II and a very low fraction of Type I in the WQ, AC, and FC samples. The presence of a high fraction of Type V in the FC sample was related to the type and fraction of each variant. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

The relatively insufficient knowledge of the deformation behavior has limited the wide application of the lightest structure material-Mg alloys. Among others, bending behavior is of great importance because it is unavoidably involved in various forming processes, such as folding, stamping, etc. The hexagonal close-packed structure makes it even a strong texture-dependent behavior and even hard to capture and predict. In this regard, the bending behaviors are investigated in terms of both experiments and simulations in the current work. Bending samples with longitudinal directions inclined from the transverse direction by different angles have been prepared from an extruded AZ31 plate, respectively. The moment-curvature curves and strain distribution have been recorded in the four-point bending tests assisted with an in-situ digital image correlation (DIC) system. A crystal-plasticity-based bending-specific approach named EVPSC-BEND was applied to bridge the mechanical response to the microstructure evolution and underlying deformation mechanisms. The flow stress, texture, twin volume fraction, stress distribution, and strain distribution evolve differently from sample to sample, manifesting strong texture-dependent bending behaviors. The underlying mechanisms associated with this texture dependency, especially the occurrence of both twinning and detwinning during the monotonic bending, are carefully discussed. Besides, the simulation has been conducted to reveal the moment-inclination angle relation of the investigated AZ31 extruded plate in terms of the polar coordinate, which intuitively shows the texture-dependent behaviors. Specifically, the samples with longitudinal directions parallel to the extruded direction bear the biggest initial yielding moment.

The microstructure and related property evolution induced by dynamic recrystallization (DRX) and static recrystallization (SRX) in thermo-mechanical process are two critical factors for the metal forming. The DRX and SRX are determined by the grain level deformation and sequentially coupled. In order to fully capture the microstructure and mechanical property evolution, a crystal plasticity finite element based modelling method for DRX and SRX is proposed in the current work. The grain level deformation is calculated with crystal plasticity which is coupled with the recrystallization model straightforwardly, and both the grain deformation and microstructure evolution are updated simultaneously. The proposed method is validated with discontinuous DRX experiments and the effects of initial deformation conditions are well-captured. Two controversial mechanisms for recrystallization microstructure evolution, i.e. oriented nucleation and growth selection, are discussed in the current framework with the advantages of accurate grain level deformation and interaction predictions. Furthermore, the sequentially coupled DRX and SRX are modelled seamlessly in the current work which provides a critical method for fully integrated thermo-mechanical processes analysis.

The complex behavior of glassy polymers, characterized by temperature-, rate-, time-, and stress-state dependencies, remains to be fully elucidated. Existing constitutive theories have modelled this phenomenon with varying degrees of success. To date, no generally accepted theory can fully and accurately describe the coupled thermo-mechanical response of glassy polymers over a wide temperature range, encompassing low to high strain rates, various time scales, including transient and long-term processes. In this work, a novel, fully thermodynamically coupled constitutive theory is proposed to address these challenges. Unlike previous models, this theory offers a comprehensive approach to time-dependent behaviors, extending the classical elastic-viscoplastic thermo-mechanical theories of Anand and his co-workers [68,69] and of Bouvard et al. [71] to more accurately predict the time-dependent behavior of glassy polymers. Specifically, a new static recovery term is introduced into the internal strain evolution equation, introducing only one additional parameter. The effectiveness of the proposed theory is demonstrated through detailed comparisons with experimental data for polycarbonate (PC) and polymethyl methacrylate (PMMA) under different external environments and various stress states. The simulation results confirm the theory's ability to predict thermodynamically coupled viscoplastic responses across different temperatures and strain rates, while also highlighting its unprecedented accuracy in modeling time-dependent phenomena, such as creep and stress relaxation.

In this study, numerical simulations and experimental validations of the simulation of hemispherical punch tests for AA7075-O aluminum sheets with various sample widths are presented. It is convincingly believed in literature that a finite element (FE) based forming limit diagram (FLD) can be predicted very well using various time-dependent criteria. This matter has been investigated and securitized deeply and the FE-based FLD was predicted using three time-dependent criteria and compared with the experimental FLD. Results show that two of the three criteria could predict the relatively appropriate shape of the FLD while one of them has failed to match. Aside from using FE simulation to predict the FLD, an analytical method, namely, Marciniak-Kuczynski (M-K) was also used to make a better evaluation about the capability of the finite element method (FEM) to predict FLD. Among the FE-based FLDs, the one predicted using the Martinez-Donaire et al., 2014 was found to be close to the one predicted using the M-K method. Although, the main objective of this paper is to investigate the capability of the FEM to predict an FLD for AA7075-O aluminum sheets, the fracture behavior for each case was predicted using a unified fracture model. Several computer runs were executed to perform the tests and reproduce the experimental results. The aim of this study was to discuss the simulation of hemispherical punch tests and analyze the numerical results and compare them with the experimental and analytical methods. It was observed that the experimental FLD can be reproduced using various time-dependent criteria in a relatively appropriate manner but with limitations especially at the equibiaxial stress state. These limitations were scrutinized and discussed in detail by comparing the results with experimental and analytical calculations.

A physically-based constitutive model for predicting the mechanical response of amorphous glassy polymers at room temperature and low strain rates was established within the frame of thermodynamics and kinematics. In our previous work (Lan et al., 2022b), the concepts of permanent entanglement (PE) and dynamic entanglement (DE) were utilized to reproduce the complicated behavior of amorphous glassy polymers from quasi-static to dynamic loading at temperatures from below to near the glass transition temperature. PE formed by the coiling of macromolecular chains is relatively stable and contributes to the yield and unloading behavior. DE formed by the weak interaction between monomers of adjacent segments is unstable and contributes to the macroscopic yield peak and strain hardening. However, due to including many parameters, the model is not easy to apply in practice. In this work, by ignoring the influence of temperature, the previous model (Lan et al., 2022b) was simplified. Taking polycarbonate (PC) and polystyrene (PS) as examples, the simplified model focused on the macroscopic mechanical behavior under simple compression and cyclic simple compression, analyzed the effects of mesh and specimen size on the evolution of shear bands under plane strain compression, and compared the obvious differences in localized deformation of these two types of amorphous polymers under plane strain compression. In addition, the forging process of PC at room temperature was simulated. By comparing the predictions with the experiments, it is demonstrated that the simplified model can reproduce the macroscopic mechanical response of amorphous polymers under simple compression, cyclic simple compression, plane strain compression and forging.

The high ductility of Mg-Li alloy has been mainly ascribed to a high activity of pyramidal slip to accommodate plastic strain. In the present study, however, a quantitative analysis reveals that Li-addition can only slightly stimulate the activation of pyramidal slip under compression along the normal direction of a hot-rolled Mg-4.5 wt.% Li plate, with a relative activity of approximately 18%. Although the limited activity of pyramidal slip alone cannot accommodate a large plastic strain, it effectively reduces the number of {101¯1}−{101¯2} double twins, which are believed to be favorable sites for crack initiation. The evidently reduced activity of double twins leads to a lower cracking tendency, and therefore improves ductility.

In this work, we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy, which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 K. The deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation study. The results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K, whereas at 77 K, vague grain surfaces dominate, indicating the simultaneous operation of multiple slip systems. Transmission electron microscopy (TEM) analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature, confirming the activation of multiple slip systems. The accumulation of dislocations facilitated by these multiple slip systems, combined with the high dislocation density, contributes to strain hardening and remarkable uniform elongation at 77 K. A modified dislocation density-based crystal plasticity model, incorporating the effect of grain boundary hardening (GBH) and temperature, was developed to gain a better understanding of the underlying mechanisms governing alloy's strength and plasticity. The GBH effect significantly enhances statistically stored dislocation (SSD) density and screw dislocation proportion, which promote homogeneous deformation and enhance strain hardening capacity at cryogenic temperature. These findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.

Cyclic loading behavior, such as cyclic bending, is unavoidably involved in various forming processes and the service of end products. Understanding the mechanical behavior of magnesium (Mg) alloys under cyclic bending is essential for promoting their application. Despite existing research, the microscopic mechanisms at play during cyclic bending, specifically the slip and twinning-de-twinning (TDT), warrant further exploration, which is the innovative focus of our study. To address this need, cyclic bending tests were performed on an extruded AZ31 Mg plate with the in-situ digital-image-correlation (DIC) technology. And the texture evolution was determined through electro backscattered diffraction (EBSD) measurements. Concurrently, the crystal-plasticity-based bending-specific approach, EVPSC-BEND, incorporating the TDT scheme, is utilized to interpret the mechanisms involved in cyclic bending. The impact at the macroscopic level is manifested in asymmetric cyclic moment-curvature curves, stress-strain distribution, and shifting of the neutral layer. The developed textures at different regions of the beam and the twin volume fraction distribution further directly illustrate twinning-de-twinning behaviors. Particularly, the upper and lower halves of the beam experience very distinct cyclic behaviors simultaneously. The upper half experiences a twinning, detwinning, and twinning cycle, while the lower half experiences a twin-free, twinning, and detwinning cycle. Additionally, through modeling the cyclic bending with different initial textures, the strong texture dependence has been revealed. The behaviors of magnesium alloy beam under cyclic bending discovered in this work can shed light on the application of Mg alloys, such as forming processes and service of end product.

As a significant means of plastic deformation in polymers, shear bands play a crucial role in material failure and performance optimization. In this paper, the finite element method is utilized to numerically investigate the morphology of shear bands in an amorphous polymer plate under plane strain four-point bending. Amorphous polymers are characterized by the elastic-viscoplastic constitutive relationship that takes into account the effect of pressure on yielding, including intrinsic softening and subsequent orientation hardening. The impact of material parameters including intrinsic softening, orientation hardening, and initial imperfections on the evolution of shear bands and the undulations of the specimen’s surface are explored in detail. In addition, the physical mechanisms responsible for the detour and strength decay of shear bands after passing the intersections are described. It appears that intrinsic softening is the driving force promoting the detour of shear bands at intersections, while orientation hardening is the driving force inhibiting the detour. By comparing the simulations with experimental observations, it is demonstrated that the model can qualitatively depict the morphology of the shear band during the four-point bending of amorphous glassy polymers.