Kink Band Formation Research Articles

Obtaining the longitudinal compressive response of unidirectional laminate composites from fiber misalignment micrographs through machine learning

The longitudinal compressive behavior of unidirectional composite laminates with fiber waviness is highly complex and plays a crucial role in determining final failure of composites. Evaluating this behavior, especially considering nonlinear failure mechanisms like kink-band formation, typically requires computationally expensive finite element analysis, which is impractical for large-scale quality inspection. To address computational challenges, this paper developed a new computational framework using Convolutional Neural Network (CNN) models, providing an ultra-efficient prediction of the entire stress–strain curve of composites with fiber waviness. The CNN models were trained on simulation data generated from an experimentally validated mesoscale finite element model. The microstructures of the composites with fiber waviness were taken from realistic micrographs, resulting in diverse stress–strain curves. The proposed CNN models showed high accuracy and efficiency for predicting the highly nonlinear stress–strain curves of the composites, which can be employed as a real-time evaluation method of the criticality of fiber waviness.

Mechanical Microdeformation and Kink–band Formation in Mica from the Colônia Impact Crater, São Paulo, Brazil

A comprehensive examination using a transmitted light optical microscope was conducted to analyze the morphology and geometric parameters of kink band development in mica from the Colônia impact crater's crystalline basement rocks. Significant differences were observed between kink bands formed perpendicular and parallel to the [001] plane. Kink bands perpendicular to the [001] are narrow and elongated, exhibiting two distinct coplanar orientations with regular spacing and parallel planar fractures, which suggest a slip-dislocation strain mechanism. In contrast, kink bands parallel to the [001] plane exhibit a greater variety of shapes and a more complex internal structure. These kink bands can be grouped into six types: sigmoidal-shape, S-shape, lenticular-shape, Z-shape, Z-shape with internal dislocation, and Z-shape with internal rotation. The deformation patterns in these kink bands indicate two primary processes: flexural and shear strain. The most notable deformations induced by these strain mechanisms include the curvature of cleavage lamellae, delamination cracks, and fractures along the boundaries of kink bands. More severely deformed kink bands exhibit dislocation, rotation, and partial obliteration of internal cleavage lamellae. These characteristics differ from those of typical kink bands in tectonically deformed rocks, thereby reviving the longstanding debate regarding their potential use as alternative evidence in impact cratering investigations.

Dynamic Strength and Fragmentation of Highly Oriented Ti3SiC2 under Multiaxial Compression

MAX phases are distinguished by their unique kink band formation, a distinct deformation mechanism in layered materials. This study explores the influence of global grain orientation c-axis, strain rate, and stress state on the compressive response of highly oriented Ti3SiC2 through experimental methods. A Kolsky (or split-Hopkinson) bar is employed to evaluate the dynamic compressive response under uniaxial and biaxial (planar confinement) conditions under 102s-1 strain rate. Macroscopic ultra-high-speed visualization during loading and microscopic post-mortem fractography reveal that confinement states significantly impact both macroscopic failure patterns and microscopic fracture mechanisms. Notably, biaxial loading with dynamic load edge-on to the grains and 80MPa planar confinement along the layers resulted in the highest dynamic compressive strength observed (1636±136MPa), a 66% increase compared to the unconfined uniaxial dynamic condition. The planar confinement appears to delay crack propagation and enhance inelastic deformation.

Effect of annealing temperature on the microstructure and mechanical properties of Al0.2CrNbTiV lightweight refractory high-entropy alloy

The DSC analysis and heat treatment of the newly proposed Al0.2CrNbTiV lightweight refractory high-entropy alloy prepared by vacuum arc melting was investigated, and the evolutions of the microstructure and mechanical properties of the alloy after homogenization annealing at 650 °C, 850 °C and 1050 °C for 12 h were analyzed. The results show that the Al0.2CrNbTiV high-entropy alloy could maintain stable BCC solid solution structure from room temperature to 800 °C. The alloy annealed at 650 °C exhibited simple BCC structure with coarse equiaxed grains; after annealing at 850 °C, fine acicular and irregular block-like C14 Laves phases were uniformly precipitated in the grain and grain boundaries, meanwhile, the C14 Laves phase get coarser with the annealing temperature increased to 1050 °C. With the increase of annealing temperature, the microhardness of the Al0.2CrNbTiV alloy increased first and then decreased, reaching the maximum value of 692 HV after annealing at 850 °C. Due to the high dislocation density and the formation of kink bands, the alloy annealed at 650 °C showed a good combination of plastic and strength, with the work hardening ability strengthened simultaneously, the compressive yield strength could be up to 1454 MPa, with strain >50 %. Due to the precipitation of the hard and brittle C14 Laves phase, the load-bearing capacity of the alloy was reduced after annealing at 850 °C and 1050 °C. However, the wear resistance of the alloy also improved with the presence of the hard phase. The friction coefficient of Al0.2CrNbTiV alloy annealed at 650 °C is 0.67, with the abrasive wear acting as the main wear mechanism, and the alloy after annealing at 850 °C shew the best wear resistance, with the friction coefficient of 0.63, and delamination wear mechanism.

Generalized grain boundary constitutive description implemented in a strain-gradient large-strain FFT-based formulation: Application to nano-metallic laminates

This paper presents a general treatment of grain boundary constitutive behavior in the context of strain-gradient (SG) plasticity, and its numerical implementation in a large-strain (LS) elasto-viscoplastic (EVP) fast Fourier transform (FFT)-based micromechanical model. Two novel grain boundary constitutive equations are proposed, allowing for more accurate description of the Burgers vector flow at the grain boundary. The capabilities of the generalized SG-LS-EVPFFT formulation are illustrated for the case of kink-band formation during layer-parallel compression of nano-metallic laminates (NMLs), requiring consideration of the interaction between dislocations and interfaces.

Comparison of the in situ compressive behavior of carbon fibers woven ply laminates exposed to one‐sided heat flux: Thermoplastic versus thermosetting composites

AbstractThis study investigates the influence of a combined thermal heat flux (imposed by a cone calorimeter) and a compressive loading on the deformation and damage mechanisms within quasi‐isotropic carbon fibers reinforced thermoplastic (polyetherether ketone [PEEK] and polyphenylene sulfide [PPS]) and thermosetting (epoxy) laminates. First, thermogravimetric Analyses conducted under nitrogen provide valuable information on the thermal decomposition of these materials depending on the matrix nature (580–510°C and 350°C, respectively) which is a key factor to explain the mechanical behavior under fire conditions. Second, under the same testing conditions (creep loading under a 50 kW/m2 heat flux), the time to failure is about 17 times as high (C/PEEK), twice as high (C/PPS) with respect to C/epoxy laminates. At the ply scale, the exposure of thermoplastic matrices (PEEK and PPS) to a 50 kW/m2 heat flux causes softening and thermal decomposition, facilitating the micro‐buckling of fiber bundles in matrix‐rich areas. At the laminates scale, this mechanism ultimately leads to the formation and propagation of plastic kink bands in the transverse direction. In epoxy‐based laminates, the onset of matrix pyrolysis occurs at lower temperatures (350°C) during thermal aggression, and thermal decomposition has started in all the plies of the laminates. Combined with the low ductility of the epoxy matrix, the compressive response is elastic‐brittle and results from the buckling of 0° plies outside the thermally‐damaged area.Highlights Study on the compression of polymer composites exposed to a 50 kW/m2 heat flux. The influence of the matrix nature (thermoplastic vs thermoset) is discussed. Time to failure is about 17 times higher in C/PEEK compared to C/Epoxy. Plastic kink bands propagate in thermoplastic composites at T > Tg. C/Epoxy laminates undergo buckling outside the thermally damaged area.

The abnormal deformation behaviors in commercial pure Ti during high speed compression

The effect of high speed compression on the deformation behaviors of pure titanium (Ti) was investigated in this paper. The results indicated that deformation twinning dominated the entire deformation process. In addition to the commonly observed twinning modes 101̅2<101̅1>,112̅1<112̅6>and 112̅2<112̅3>twinning, the uncommon twinning modes 101̅1<101̅2>, 112̅4<224̅3> twinning, and a rare twinning mode 112̅3<112̅2> twinning which has not been reported in previous literature, were observed. The 112̅3<112̅2> twinning presented an orientation relationship of 87° <101̅0>. Moreover, deviations from the ideal twinning relationship were observed in some twins which might due to the deformation induced dislocation-twin interactions. Alongside twinning, high angle kink bands with a misorientation of 61°<71017̅3> were locally activated to accommodate the deformation. These abnormal deformation behaviors, including the formation of unusual twins and high angle kink bands, occurred in grains that were less favorable for triggering common dislocation and twinning modes, based on the Schmid factor calculations. The high strain rate during high speed compression limited heat dissipation time and generated additional energy, thereby enhancing the flow stress and raising the temperature, which facilitated the occurrence of these abnormal deformation behaviors.

Computational analysis of the failure mechanisms of a laminated composite in double-edge notch compression configuration

This manuscript presents a combined experimental–computational investigation of the compression failure response of laminated composites in double-edge notch compression (DENC) configuration. Analysis of in-situ and post-test DENC experiment results indicates the presence of multiple failure mechanisms, including ply splitting, delamination, and compression kink bands. In order to characterize the onset, growth, and interplay of the critical and subcritical damage mechanisms, a multiscale progressive damage analysis approach is implemented. A nonlocal multiscale damage model explicitly tracks the intraply failure mechanisms that lead to the formation and propagation of kink bands in the specimen. A cohesive zone model is used to track initiation and progression of ply splitting in the specimen. The splitting model was implemented using implicit finite element simulations and deployed with a pre-crack insertion technique to reduce simulation time while preserving prediction accuracy. Model parameters are calibrated based on available calibration data and measurements. The effects of split location and growth characteristics on model predictions are studied. The computational model along with a suite of experiments were employed to study the formation, growth and interactions of damage mechanisms in the composite specimens subjected to compression loading. The onset of matrix damage is not clear from the experimental images but the model predicts early onset around the onset time of splits which greatly reduce the stress concentration at the notches. Analysis of acoustic emission energy experimental data indicate that observable compression failure mechanisms are not causing nonlinearity consistently exhibited in the experiment responses. Simulation results demonstrate the capability of the multiscale modeling approach to predict critical kink bands and sub-critical matrix cracking and splitting in the DENC specimens while reducing computational cost compared to a direct numerical simulation of fibers and matrix.

New Insight into Bulk Structural Degradation of High-Voltage LiCoO2 at 4.55 V.

The aggravated mechanical and structural degradation of layered oxide cathode materials upon high-voltage charging invariably causes fast capacity fading, but the underlying degradation mechanisms remain elusive. Here we report a new type of mechanical degradation through the formation of a kink band in a Mg and Ti co-doped LiCoO2 cathode charged to 4.55 V (vs Li/Li+). The local stress accommodated by the kink band can impede crack propagation, improving the structural integrity in a highly delithiated state. Additionally, machine-learning-aided atomic-resolution imaging reveals that the formation of kink bands is often accompanied by the transformation from the O3 to O1 phase, which is energetically favorable as demonstrated by first-principles calculations. Our results provide new insights into the mechanical degradation mechanism of high-voltage LiCoO2 and the coupling between electrochemically triggered mechanical failures and structural transition, which may provide valuable guidance for enhancing the electrochemical performance of high-voltage layered oxide cathode materials for lithium-ion batteries.

High-temperature strength and kink-band formation in mille-feuille-structured Ti/FeTi eutectic alloys

To develop ultrahigh-strength and lightweight structural materials, the temperature dependence of the deformation behavior of Ti/FeTi eutectic alloys was examined using compression tests. An extremely high yield stress of ∼2.3 GPa was obtained at room temperature accompanied by ∼5 % of plastic strain by the alignment of a “flower-like” lamellar microstructure. High stress was maintained up to 400 °C; however, the yield stress considerably decreased to ∼0.8 GPa at 600 °C. Shear deformation was observed at room temperature. However, at high temperatures, at 600 °C and above, the formation of a deformation kink band was observed for the first time as the deformation mechanism, and this resulted in a rapid decrease in yield stress. The size of the kink bands was governed by the diameter of the aligned lamellar grains, which was termed the colony size. Large kink bands were formed in the alloy containing coarse colonies, resulting in the buckling of the specimen. The introduction of primary β-Ti grains in the eutectic microstructure improved the ductility at low temperatures, which was only accompanied by the marginal decrease in yield stress to ∼1.9 GPa. Furthermore, the high-temperature strength of the hypoeutectic alloy at 600 °C showed a higher value of ∼1.0 GPa compared to that in eutectic alloys. The refinement of the colony microstructure of the hypoeutectic alloy suppressed the formation of kink bands. The experimental results suggest that microstructural control is extremely important for improving the high-temperature strength of Ti/FeTi eutectic alloys by increasing the formation stress of the kink bands.

Kink bands promote exceptional fracture resistance in a NbTaTiHf refractory medium-entropy alloy.

Single-phase body-centered cubic (bcc) refractory medium- or high-entropy alloys can retain compressive strength at elevated temperatures but suffer from extremely low tensile ductility and fracture toughness. We examined the strength and fracture toughness of a bcc refractory alloy, NbTaTiHf, from 77 to 1473 kelvin. This alloy's behavior differed from that of comparable systems by having fracture toughness over 253 MPa·m1/2, which we attribute to a dynamic competition between screw and edge dislocations in controlling the plasticity at a crack tip. Whereas the glide and intersection of screw and mixed dislocations promotes strain hardening controlling uniform deformation, the coordinated slip of <111> edge dislocations with {110} and {112} glide planes prolongs nonuniform strain through formation of kink bands. These bands suppress strain hardening by reorienting microscale bands of the crystal along directions of higher resolved shear stress and continually nucleate to accommodate localized strain and distribute damage away from a crack tip.

Unraveling microstructure and mechanical response of an additively manufactured refractory TiVHfNbMo high-entropy alloy

Refractory high-entropy alloys (RHEAs) have attracted considerable interest due to their elevated melting points and exceptional softening resistance. Nevertheless, the ambient-temperature brittleness and inadequate high-temperature oxidation resistance commonly restrict the processability of RHEAs. Direct energy deposition (DED) additive manufacturing technology is ideal for fabricating refractory alloys due to design flexibility and oxygen-free environment. In this work, a novel Ti41V27Hf13Nb13Mo6 RHEA was successfully manufactured by DED, and a comprehensive investigation was conducted to explore the microstructure evolution and mechanical response during tension. The as-deposited RHEAs exhibit a grain-size graded microstructure with a body-centred-cubic (BCC) matrix and precipitates. Increasing laser energy density suppressed the grain boundary precipitation, effectively enhancing the ambient-temperature tensile ductility to ∼11.3%. The optimized specimens achieved an unprecedented yield strength of ∼1.2 GPa among the DEDed RHEAs, which can be attributed to a significant solid solution strengthening from the volume misfit of 5.03%. We revealed that dislocation interactions maintained the working hardening capacity. Moreover, in-situ characterization indicated that slip transfer, grain rotation, and kinking accommodated the plastic deformation. Crack nucleation was caused by slip inhibition at grain boundaries and dislocation pile-ups at intragranular precipitates. The kink band formation relieved stress concentration induced by intragranular precipitates and promoted a ductile fracture. These exceptional outcomes provide opportunities for additive manufacturing RHEAs and greatly advance understanding of their strengthening and deformation mechanisms.

New kink-band formation mechanism discovered in Zn-Al alloy with mille-feuille microstructure

The discovery of kink-band strengthening in some Mg-alloys has focused attention on the development of mille-feuille-structured alloys composed of alternating stacks of plate-like soft and hard phases. In this study, we focused on the Zn-6.0mass%Al alloy that is composed of hcp-Zn and fcc-Al, and is used as a coating material on hot-dip galvanized steel sheet for automobile. The deformation behavior was examined by using directionally solidified crystal. As expected, kink bands formed in alloys but two different kink-band formation mechanisms were identified. One is a classical mechanism which involves the formation of an array of dislocations perpendicularly aligned with their slip planes. The other is a new mechanism which has never been reported in any materials before, and a prior {11 2¯ 2} pyramidal slip in the Zn matrix phase acts as the source, with dissociation of the <112¯3¯> dislocation supplying the <11 2¯ 0> dislocation for kink-band formation. The latter newly found mechanism introduces fine kink bands uniformly into the specimen, which effectively causes kink-band strengthening during subsequent deformation compared to kink bands introduced by conventional formation mechanism. This study provides a new strategy for enhancing kink-band strengthening in alloys by the control of the morphology of kink bands.

Microscale and mesoscale modeling for compressive failure in unidirectional carbon fiber reinforced polymer composites with random distribution of fiber misalignments

AbstractCompressive strength and failure mode of carbon fiber reinforced polymer (CFRP) composites are affected by the severity of fiber misalignment. In this paper, numerical models based on computational micromechanics are proposed to investigate the correlation between fiber misalignment and compression failure. A single‐fiber micromodel including fiber, matrix, and interface phases is first developed to capture the influence of misalignment severity on the material failure mode. The failure longitudinal stress distribution in the fiber predicted by the micromodel indicates that the failure mode depending on the initial misalignment can be identified as uniform compression failure, compression‐bending combination collapse, and fiber buckle. A mesoscale 2D model with multiple fibers is then constructed to investigate the kink band formation. This model takes into account the distribution of fiber misalignments to capture the key geometric features of fiber misalignment that influent the compression failure in realistic composite materials at the structural scale. The results show that fiber misalignment angle amplitude, misalignment dispersion (characterized by the standard deviation), and misalignment wavelength are the key parameters of fiber misalignment, which have significant effects on compression strength and kink band geometry.Highlights Single‐fiber model to capture the effect of misalignment severity on failure mode. Multi‐fiber model with randomly distributed fiber misalignments. Failure mode depending on the severity of initial misalignment was identified. Key parameters of misalignment on compression strength and kink band geometry.

Microstructure evolution, grain refinement, and mechanical properties of a metastable β titanium alloy during cold rolling and recrystallization annealing

While grain refinement is a promising approach for enhancing the performance of structural alloys, an improved understanding of the mechanisms underlying grain-refinement processes and their influence on mechanical properties is required. Therefore, in this study, we investigated the microstructure and mechanical properties of the single β-phase TB18 alloy (Ti-5.3Cr-4.9Mo-4.9 V-4.3Al-0.9Nb-0.3Fe) during cold rolling and annealing, with dislocation slip as well as kink and shear band formation identified as the main deformation mechanisms during the cold-rolling process, which ensured good workability of the cold-rolled plate at room temperature. Shear bands formed preferentially in γ-fiber (〈111〉//normal direction (ND))-oriented grains such as {111}〈110〉 grains. The high density of subgrains and dislocations in the shear bands and surrounding regions promoted nucleation of the recrystallized grains, resulting in an increased nucleation rate and grain refinement. The texture after cold rolling mainly had rotated cube {001}<110> and {111}<110> components. During subsequent annealing, these components rotated to α*-fiber ({11h} < 1 2 1/h>) and {111}〈112〉 components, respectively, thereby forming the final recrystallized texture. Thus, cold rolling and recrystallization annealing of the TB18 alloy resulted in a fine microstructure with a mean grain size of 25 μm and excellent mechanical properties. In particular, the ultimate tensile strength and elongation of the pure β microstructure increased to 850 ± 2 MPa and 28.8 ± 2.2%, respectively. Thus, these results indicate that cold rolling and recrystallization annealing could be considered as promising techniques for developing metastable β titanium alloys with enhanced mechanical properties.

Characterizing compressive failure mechanisms and their transitions in woven composites under on and off-axis loading

The compressive failure of fiber-reinforced composites is complex, occurring via multiple mechanisms depending on the loading angle with the fiber directions. This work is aimed at the detailed characterization and understanding of this dependence in a 2 × 2 epoxy/carbon twill woven composite. Reported are the results of a variety of on-axis and off-axis compressive tests with loading angles ranging from 0°to 45°, carried out as per ASTM standards. The tests show that for angles from 0°to 10°, no appreciable change in compressive strength occurs. Failure in the load aligned tows is dominated by out of plane shear failure and out of plane fiber kinking. The behavior is very brittle, consisting of a sharp peak load immediately dropping to a non-zero residual stress plateau. Extensive micro-cracking in the transverse tow is also observed. Between 10°and 25°many transitions occur, including increased ductility, pre-peak non-linearity, increasing width of the out-of-plane fiber kink band, more gradual post-peak load decrease, and an increase in the residual stress. The lowest strength occurs at 45°where the behavior is completely ductile and failure occurs by in-plane fiber kink band formation. A correlation between the in-plane shear stress and kink band width appears to exist. The maximum stress based strength envelope theory captures this loading angle dependence of strength. The findings are crucial for designing multi-directional woven composite laminates subjected to compressive loading, and for the validation of computational models.

Characterization of Failure Behavior in Unidirectional Fiber-Reinforced Polymer via Off-Axis Compression on Small Block Specimens.

An experimental investigation was focused on the failure behavior of unidirectional fiber-reinforced polymers when subjected to combined longitudinal/transverse compression and in-plane shear due to off-axis loading. Block-shaped and end-loaded specimens, spanning ten different fiber orientations (0°, 5°, 10°, 15°, 20°, 30°, 45°, 60°, 75°, and 90° with respect to the loading direction), were loaded to ultimate failure using a dedicated fixture. Different failure modes, including longitudinal compression, in-plane shear, and transverse compression, were identified, along with distinctive characteristics of the corresponding failure envelopes. Four physically based failure theories-Hashin, Camanho, Puck, and LaRC05-were subjected to a comparative analysis. Criteria derived from the concept of the action plane consistently outperformed in describing matrix-dominated failures, providing both qualitative and quantitative predictions of failure stresses and fracture plane orientation. However, for fiber-dominated failures, these theories seem to fall short in providing satisfactory predictions, particularly in accurately describing the influence of shear on fiber compression failure. Although criteria based on fiber-kinking theory can reasonably explain the formation of kink bands, they tend to yield overly conservative results. Recalibrations and minor refinement based on experimental results were implemented, leading to an improved agreement. Finally, the constructive role of off-axis compression tests in characterizing the failure behavior of unidirectional composites is discussed.

Micromechanics of kink-band formation in bimetallic layered composites

Bimetallic layered composites with ultrathin layers possess high strength and hardness, and excellent shock resistance and radiation damage tolerance. However, they are prone to deformation localization and readily form kink-bands when subjected to layer parallel compression. Following this, we carried out extensive plane strain finite element finite deformation analyses to understand and rationalize the experimentally observed kink-band formation in these composites. In the calculations, both constituent materials were assumed to follow a rate-independent isotropic elastic-plastic constitutive relation with an ad-hoc thickness dependent yield strength. Our results demonstrate that in these composites, layer refinement, together with the strength differential between the layers of the constituent materials, is sufficient to trigger kink-banding. Importantly, this phenomenon occurs even in the absence of elastically stiff layers, geometrical imperfections (such as waviness of the layers), and extreme plastic anisotropy within the layers. Additionally, we performed parametric studies to investigate the individual effects of layer thickness, strength differential between the two constituent materials, and strain-hardenability of the materials on kink-band formation. The outcomes of our parametric studies reveal that the strain-hardenability of the constituent materials stabilizes the formation of kink-bands. Furthermore, it leads to a transition from the abrupt formation of through-width kink-bands to the onset and propagation of stable inclined wedge-shaped kink-bands, similar to the experimental observations.

Mechanisms of Shock Dissipation in Semicrystalline Polyethylene.

Semicrystalline polymers are lightweight, multiphase materials that exhibit attractive shock dissipation characteristics and have potential applications as protective armor for people and equipment. For shocks of 10 GPa or less, we analyzed various mechanisms for the storage and dissipation of shock wave energy in a realistic, united atom (UA) model of semicrystalline polyethylene. Systems characterized by different levels of crystallinity were simulated using equilibrium molecular dynamics with a Hugoniostat to ensure that the resulting states conform to the Rankine-Hugoniot conditions. To determine the role of structural rearrangements, order parameters and configuration time series were collected during the course of the shock simulations. We conclude that the major mechanisms responsible for the storage and dissipation of shock energy in semicrystalline polyethylene are those associated with plastic deformation and melting of the crystalline domain. For this UA model, plastic deformation occurs primarily through fine crystallographic slip and the formation of kink bands, whose long period decreases with increasing shock pressure.

An ambient ductile VNbTa refractory medium-entropy alloy with super rolling formability

Refractory multiple-principal element alloys (RMEAs) systems have drawn particular attentions in recent years due to their great potential for high-temperature application. However, most of RMEAs exhibit tensile brittleness, oxidation, and phase decomposition, which limit their potential applications. Hence, developing new RMEAs with excellent ductility has become one of the urgent tasks for RMEAs’ applications. Here, a ductile VNbTa equiatomic RMEA has been fabricated by vacuum arc melting. The VNbTa alloy exhibits high tension strength (σ0.2 = 1033 MPa), outstanding fracture elongation (εf >19 %), super rolling formability (>80 % thickness reduction), and work hardening at room temperature (RT). The high strength of VNbTa alloy is mainly associated with solid solution strengthening and local lattice distortion induced by the misfits of atomic sizes and mechanical moduli of various elements. The super formability of VNbTa alloy attributes to the mobility of a/2<1 1 1>-type dislocations and the formation of kink bands at RT. This study not only clarifies the phase stability, lattice distortion, strengthening, elastic and plastic mechanisms of the ductile VNbTa alloy by combining experiments and theoretical calculations, but also provides more helpful information to design RMEAs with superior ductility at room temperature.