Dislocation-mediated Plasticity Research Articles

Thermal activation and dislocation dynamics in Ti–6Al–4V alloy

The tensile stress relaxation behaviour is experimentally investigated for Ti–6Al–4V alloy across a temperature range of −60, −30, 20, 120, and 230 °C. Interestingly, the results revealed that the alloy exhibited the lowest resistance to stress relaxation at 20 °C, i.e., room temperature. This resistance was found to increase with both increasing and decreasing test temperatures. The apparent activation volume values, which indicate the dislocation mean free path, increase with strain due to a decrease in activable dislocation segments. Furthermore, these values were found to be proportional to the test temperature, resulting from higher dislocation mobility at moderate temperatures (230 °C and 120 °C) than at lower temperatures. Our experimental and analysis results indicate that dislocation-mediated plastic deformation predominates in all tested temperature conditions. However, the transition from planar to wavy dislocation configuration, observed through Transmission Electron Microscopy (TEM) between temperatures of −30 and 20 °C, along with the change in activation volume, suggests a critical temperature at which dislocation mechanism changes in the Ti–6Al–4V alloy. A rapid exhaustion of a substantial amount of mobile dislocation density, which significantly contributes to time-dependent deformation was observed at 230 °C. These findings provide valuable insights into the mechanisms underlying the stress relaxation behaviour of Ti–6Al–4V alloy at different operational temperatures, offering practical implications for improved alloy design and manufacturing processes.

Multiscale modeling of dislocation-mediated plasticity of refractory high entropy alloys

Refractory high entropy alloys (RHEAs) have drawn growing attention due to their remarkable strength retention at high temperatures. Understanding dislocation mobility is vital for optimizing high-temperature properties and ambient temperature ductility of RHEAs. Nevertheless, fundamental questions persist regarding the variability of dislocation motion in the rugged energy landscape and the effective activation barrier for specific mechanisms, such as kink-pair nucleation and kink migration. Here we perform systematic atomistic simulations and conduct statistical analysis to obtain the effective activation barriers for the mechanisms underlying various types of dislocation motion in a typical RHEA, NbMoTaW. Moreover, a stochastic line tension model is developed to calculate the activation barrier with substantially reduced computational costs. By incorporating the effective activation barriers into the crystal plasticity model, a multiscale simulation framework for predicting the mechanical properties of RHEAs is established. The ambient temperature yield strength of NbMoTaW is well-predicted by the kink-pair nucleation mechanism of screw dislocations, while the strengthening originating from screw dislocations does not predominate at high temperatures. Our work provides a robust foundation for atomistic studies of effective dislocation behaviors in random solution solids, elucidating the intricate relationship between microscopic mechanisms and macroscopic properties.

Molecular dynamics informed calibration of crystal plasticity critical shear stresses for the mesoscopic mechanical modeling of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) single crystal

An extension of a constitutive law for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is proposed with a focus on the calibration of a crystal plasticity law. TATB, a highly anisotropic energetic molecular crystal used in explosive formulations, can be subjected to high-pressure and high-temperature conditions, either under high strain-rate deformation or shock loading. The existing thermodynamically consistent model, fully informed by molecular dynamics (MD) simulations, includes nonlinear elasticity as well as a phase-field by reaction pathway formalism under large strain for the modeling of TATB behavior upon pressure as well as its well-known twinning–buckling deformation mechanism. However, it has been observed that TATB single crystal can accommodate large deformations through dislocation-mediated plasticity, a feature not included in the mesoscale model. In the present work, we take advantage of the microscopic flow surface, previously computed through MD calculations, to calibrate a crystal plasticity law, extending the capability of the continuum model currently limited to low velocity impacts and moderate strain rate. Indeed, the microscopic flow surface, defined as a 3D stress-at-first-defect-nucleation contains all information about TATB single crystal mechanical response under directional shear loading, including twinning, buckling, and plastic events. The calibration process uses differential evolution optimization to calibrate TATB basal and transverse slip systems critical stresses to reproduce the microscopic flow surface. Finally, the response of a TATB single crystal to directional loading is investigated in order to evaluate the new model.

Atomistic modeling of plastic deformation in BCC niobium nanowire under bending

Design of high-performance nanodevices require nanowires with optimized bending properties, which relies on a thorough understanding of the mechanical behavior of nanowires. To explore the mechanism underlying bending plasticity of the nanowire, we adopted a 〈110〉-oriented body-centered cubic (BCC) Nb nanowire as the model system and performed bending tests at various temperatures by means of molecular dynamics simulation. Our results reveal that the BCC Nb nanowire bends plastically and homogeneously into a smoothed arc shape with significant curvature by slip of perfect dislocations, showing excellent bending plasticity and toughness. The generated dislocations are identified as geometrically necessary dislocation for accommodating the strain gradient related to bending, and they accumulate linearly with the bending angle to a value of an order of 1017 m−2. Temperature dependence was found in both elastic modulus and yield strength of the nanowire. In particular, we find that a completely dislocation-mediated plasticity at high temperature changes into a deformation mechanism involving predominant dislocation slip plus additional anti-twinning as temperature is reduced. Both development of high dislocation density and reduced mobility of dislocation at low temperature contribute to the initiation of anti-twinning. Our findings not only enrich the current understanding of deformation behavior of BCC nanomaterials under non-uniaxial load, but also provide valuable information for design of flexible and stretchable nanodevices based on metallic nanowires.

Dislocation-mediated plasticity in the intermetallic SmCo5 phase

The intermetallic SmCo5 phase is well known for its unique magnetic properties, but so far, research on the mechanical properties and the underlying lattice defects is comparably scarce. This study aims to investigate the deformation mechanisms of the SmCo5 phase through nanoindentation and micropillar compression on two single crystals with different orientations. We find two active slip systems in compression, the pyramidal slip system {2 1¯1¯1¯} 〈2¯ 1 1 6¯〉 and the basal slip system (0 0 0 1) [2 1¯1¯ 0]. Additionally, basal and pyramidal stacking faults and partial dislocations were observed by transmission electron microscopy. Using ab initio and atomistic modelling we investigated the underlying defect structures and energy barriers. These allowed us to rationalize the observed slip systems and suggest that the pyramidal stacking faults may form by a synchro-shear slip mechanism. Our findings also provide a basis to understand the deformation behaviour of structurally related phases in the Sm-Co system, such as Sm2Co7, which comprises SmCo5 and Laves SmCo2 building blocks.

A dislocation-density-based crystal plasticity model for FCC nanocrystalline metals incorporating thermally-activated depinning from grain boundaries

A novel dislocation-density-based crystal plasticity model for nanocrystalline face-centered cubic metals is developed based on the thermally-activated mechanism of dislocations depinning from grain boundaries. Dislocations nucleated from grain boundary dislocation sources are assumed to be the primary carriers of plasticity in the nanocrystals. The evolution of the dislocation density thereby involves a competition between the nucleation of dislocations from grain boundary defect structures, such as ledges, and the absorption of dislocations into the grain boundary via diffusion processes. This model facilitates the simulation of plastic deformation in nanocrystalline metals, with consideration of the initial microstructure resulting from a particular processing method, to be computed as a direct result of dislocation-mediated plasticity only. The exclusion of grain boundary-mediated plasticity mechanisms in the formulation of the crystal plasticity model allows for the exploration of the fundamental role dislocations play in nanocrystalline plasticity. The combined effect of average grain size, grain size distribution shape, and initial dislocation density on the mechanical performance and strain-rate sensitivity are explored with the model. Further, the influence of the grain boundary diffusivity on post-yielding strain-hardening behavior is investigated to discern the impact that the choice of processing route has on the resulting deformation response of the material.

Atomic mixing mechanisms in nanocrystalline Cu/Ni composites under continuous shear deformation and thermal annealing

Molecular dynamics (MD) simulations are used to reveal the mechanisms of defect substructure evolution and atomic mixing in nanocrystalline Cu/Ni composites under severe shear deformation and subsequent thermal annealing. A continuous shear scheme of MD simulation utilizing an on-the-fly periodic boundary adjustment approach enables it to reach any large shear strain. The comprehensive evaluation on the evolution of dislocation structures at various strain states indicates partial dislocation-mediated plastic deformation and triple junction slide via partial dislocation nucleation and emission from triple junctions and grain boundaries. The analysis of atomic structures in unique mixing regions suggests that triple junction sliding can result in a long-range region of atomic mixing facilitated by net dislocation flux, which is the key mechanism of atomic mixing in nanocrystalline Cu/Ni composite under severe shear, while dislocation emissions at interfaces result in short-range mixing. It is also found that thermal annealing causes the evolution of non-equilibrium defect substructures which assists atomic mixing.

Grain refinement induced by grain boundary segregation in FeNiCrCoCu high-entropy alloys using molecular dynamics simulation of nanoindentation

Atomistic simulation of nanoindentation is performed to investigate the effect of Cu segregation at grain boundaries (GBs) on the mechanical properties of FeNiCrCoCu high-entropy alloys. Initially, a combined Monte Carlo and Molecular dynamics simulation technique is adopted to generate the models with Cu segregation, and further the cases of random Cu distribution are considered for the purpose of comparision. The dislocation density, shear strain and GB behavior in the process of nanoindentation are analyzed in detail. The results reveal that the Cu segregation at GBs leads to superiority in hardness, strength, and stiffness. Dislocation analysis shows that the sessile dislocation density is higher at the initial state for the segregation sample, while dislocation nucleation and movements are suppressed so that dislocation-mediated plasticity is weakened. Furthermore, microrotation analysis during the nanoindentation process indicates that segregation of Cu pins the GBs, thereby inhibiting GB rotation and consequently weakening GB-mediated plastic deformation. In this case, grain refinement is observed, and in good agreement with experiment results. Overall, this study provides insights into the influence of GB segregation of Cu on the mechanical properties and deformation response of FeNiCrCoCu HEAs, and highlights the importance of GB composition for tailoring high-strength materials.

Micromechanical analysis and finite element modelling of laser-welded 5-mm-thick dissimilar joints between 316L stainless steel and low-alloyed ultra-high-strength steel

As base metals (BMs), plates of 5-mm-thick low-alloyed ultra-high-strength carbon steel (LA-UHSS) with a tensile strength of 1.3 GPa and 5-mm-thick 316L austenitic stainless steel were laser-welded at two different energy inputs (EIs; 60 and 100 J/mm). The microstructural characteristics of the fusion zones (FZs) in the welded joints were examined using electron backscattering diffraction (EBSD) and transmission electron microscopy. The fine microstructural components, such as the prior austenite grain size (PAGS) and effective grain size of the fresh martensite promoted during welding, were analysed by processing the EBSD maps using MATLAB software. The micromechanical performance of the weldments was investigated using microindentation hardness (HIT) to display the mechanical responses of different zones. Uniaxial tensile testing was conducted to explore the joint strength and plasticity failure. The dominant phase structures promoted in the FZs at low and high EIs were similar, that is, martensite with a small fraction of austenite. The HIT values displayed a distinct variation in strength between different zones. The HIT values of 316L, LA-UHSS, and FZ were 1.95, 5.55, and 4.63 GPa, respectively. The PAGS increased from 45 to 70 μm with an increasing EI, and a finer martensitic grain structure with an average size of 2.62 μm was observed at high EIs. The mechanical tensile properties of the dissimilar joints at the studied EIs closely matched those of the BM 316L, demonstrating comparable yield and tensile strengths of 225 MPa and 650 MPa, respectively. This similarity can be attributed to the localized plastic tensile deformation occurring primarily within the relatively softer BM 316L, ultimately resulting in joint failure. The flow behaviour of the dissimilar joints under uniaxial tensile testing was analysed using finite element modelling to determine the stress and strain distributions. The plastic strain was mainly localised within the soft metal 316L owing to enhanced dislocation-mediated plasticity.

The effect of the structural parameters on the friction and wear properties of some FCC metals

Friction and wear are very complex thermo-mechano-chemical processes of contact interaction. For a better understanding of the mechanisms of plastic deformation affecting friction and wear, four face-centered cubic (FCC) metals (Ag, Cu, Ni, and Al) were studied using a pin-on-disk rig. The topmost surface layer presents nanocrystalline (NC) and ultrafine grain (UFG) structures with the transition to a sublayer with a lamellar structure parallel to the direction of friction. The thickness of the topmost layers is mainly determined by stacking fault energy (SFE), hydrostatic pressure, and shear stress. The thermo-mechanical control of plastic flow during the steady friction state was considered. The effective shear stress as the activation barrier, the strain rate sensitivity, and the contact temperature were calculated. The values of the strain rate sensitivity, m, indicate that NC and UFG surface layers for Ag, Cu, and Ni, exhibit low capacities for strain hardening. The friction of FCC metals in lubricated conditions is characterized by a switch from dislocation-mediated plasticity to grain boundary (GB) plasticity in the topmost surface layers. The similarity between friction with low and high coefficients of friction during dry and lubricated conditions was considered. The wear resistance of studied materials can be compared to strength improvements and easy shearing of the topmost surface layer under dry and lubricated conditions. Dislocation glide and grain growth play a key role in the hardening/softening of surface layers both in dry and lubricated conditions.

Shedding new light on the dislocation-mediated plasticity in wurtzite ZnO single crystals by photoindentation

Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations. In this study, we investigated the effects of light illumination on the dislocation-mediated plasticity in hexagonal wurtzite ZnO, a representative third-generation semiconductor material. A (0001) 45o off sample was specially designed to preferentially activate the basal slip on (0001) plane. Three types of nanoindentation tests were performed under four different light conditions (550 nm, 334 nm, 405 nm, and darkness), including low-load (60 μN) pop-in tests, high-load (500 μN) nanoindentation tests, and nanoindentation creep tests. The maximum shear stresses at pop-in were found to approximate the theoretical shear strength regardless of the light conditions. The activation volume at pop-ins was calculated to be larger in light than in darkness. Cross-sectional transmission electron microscope images taken from beneath the indentation imprints showed that all indentation-induced dislocations were located beneath the indentation imprint in a thin-plate shape along one basal slip plane. These indentation-induced dislocations could spread much deeper in darkness than in light, revealing the suppressive effect of light on dislocation behavior. An analytical model was adopted to estimate the elastoplastic stress field beneath the indenter. It was found that dislocation glide ceased at a higher stress level in light, indicating the increase in the Peierls barrier under light illumination. Furthermore, nanoindentation creep tests showed the suppression of both indentation depth and creep rate by light. Nanoindentation creep also yielded a larger activation volume in light than in darkness.

Extraordinary combination of strength and ductility in an additively manufactured Fe-based medium entropy alloy through in situ formed η-nanoprecipitate and heterogeneous microstructure

The current study investigated the mechanical properties of Fe65Ni15Co8Mn8Ti3Si (at%) medium entropy alloy (MEA), printed by laser-based direct energy deposition (DED) in the room and liquid nitrogen environments. The as-printed microstructure contains various levels of heterogeneities, including different grain sizes, dual-phase microstructure, in situ formed η nanoprecipitate, cellular structure, and elemental segregation generated during the DED process. The impact of each observed heterogeneity on the mechanical properties and the predominant deformation mechanisms were examined. The corresponding MEA revealed a high ultimate tensile strength (UTS) of ∼1.02 GPa, total elongation (TE) of ∼46%, and exceptional cryogenic mechanical properties with a UTS and TE of 1.83 GPa and 40%, respectively. According to microstructural observations, the deformation-induced phase transformation from face-centered cubic (FCC) to body-centered cubic (BCC) is the predominant strengthening mechanism at both room and liquid nitrogen temperatures in addition to solid-solution strengthening and dislocation-mediated plasticity. The non-shearable η nanoprecipitates also enhanced the mechanical properties through precipitation/stacking fault strengthening. Hetero-deformation-induced (HDI) strengthening also occurred in the presence of dual-phase microstructure, cellular microstructure, and elemental segregation in the FCC phase. This upgraded synergy of tensile strength and ductility at liquid nitrogen temperature can be explained through the phase transformation and additional activation of twinned martensite formation, which results in two-step strain-hardening behavior. The presented results expand possibilities for developing DED-processed ferrous HEAs/MEAs to overcome the strength and ductility trade-off at room and liquid nitrogen temperatures.

Competition between work hardening and softening in dislocation-mediated metallic glass matrix composites

By modulating β-phase stabilizing elements, three metallic glass matrix composites (MGMCs) with stable β-phase were developed. The mechanical behavior based on dislocation-mediated plasticity is different for the very three composites, due to the difference in the number of slip systems generated by the plastic deformation within dendrites. A quantitative model of predicting yield strengths in MGMCs is successfully established. This provides useful guidances to design ductile MGMCs for structural application at ambient temperature.

Theoretical insights into the Peierls plasticity in SrTiO3 ceramics via dislocation remodelling

An in-depth understanding of the dislocations motion process in non-metallic materials becomes increasingly important, stimulated by the recent emergence of ceramics and semiconductors with unexpected room temperature dislocation-mediated plasticity. In this work, local misfit energy is put forward to accurately derive the Peierls stress and model the dislocation process in SrTiO3 ceramics instead of the generalized stacking fault (GSF) approach, which considers the in-plane freedom degrees of the atoms near the shear plane and describes the breaking and re-bonding processes of the complex chemical bonds. Particularly, we discover an abnormal shear-dependence of local misfit energy, which originates from the re-bonding process of the Ti-O bonds and the reversal of lattice dipoles. In addition, this approach predicts that oxygen vacancies in the SrTiO3 can facilitate the nucleation and activation of dislocations with improvement of fracture toughness, owing to the reduction of average misfit energy and Peierls stress due to the disappearance of lattice dipole reversal. This work provides undiscovered insights into the dislocation process in non-metallic materials, which may bring implications to tune the plasticity and explore unknown ductile compositions.

A pseudospectral contact mechanics simulation of microindentation in two slip systems activated single crystalline material by using a homographic conformal mapping

Micromechanical behavior of two slip systems activated FCC single crystals is investigated through a pseudospectral modeling microindentation based on Dislocation Mediated Plasticity. Variational form of integral energy is evaluated by dislocations density energy, contact energy of master indenter and slave. Physical domain beneath indenter is guided to transferre into a computational domain using a homographic conformal mapping. Choosing this mapping guarantees extracting closed-form governing equations with thirty-two complex boundary conditions as remain invariant too. This is the key point that explicit integration by parts can provide requirements of imposing spectral discretization through generalized differential quadrature operators. By evaluating those operators at Guess- Lobato points, a set of algebraic equations is acquired. So, a novel framework for producing a mesh reduction scheme is handled by an efficient strong form solution. This method is fast and stable enough to calculate without emerging any aliasing. The crystal will deform with two active slip systems so that movement of contact points remain only at one direction attached to the indenter. The activity range of each slip system up to a depth of 200 microns is examined and displacement-force graphs. Good agreements are found in the results obtained from simulation compared with experiments.

Shear-band blunting governs superior mechanical properties of shape memory metallic glass composites

Metallic glass composites (MGCs) containing crystals can display tensile ductility, overcoming the catastrophic failure of bulk metallic glasses. However, MGCs containing crystals with dislocation-mediated plasticity generally undergo strain-softening, but MGCs containing shape memory crystals can exhibit strain-hardening. The origin of large ductility and strain-hardening of shape memory MGCs as well as the interactions of shear bands (SBs) with crystals remains elusive. Here, two kinds of MGCs containing crystals with dislocation-mediated plasticity or shape memory crystals with martensitic transformations are investigated. It is found that the behavior and properties of SBs in glass matrix can be significantly altered by deformation characteristics of crystals. If crystals deform via dislocations, SBs are narrow, sharp and become mature. In comparison, SBs in shape memory MGCs continuously broaden without maturing by following the growth of thick martensitic plates. Broad SBs tend to bifurcate during propagation, and bifurcated SBs further induce the formation of more martensitic variants in crystals, benefiting strain delocalization. Broadening and bifurcation of SBs cause the SB blunting, which governs the superior mechanical properties of shape memory MGCs. These findings not only deepen the understanding of SBs in glass materials, but also provide a fundamental basis to enhance their mechanical properties by engineering of blunt SBs.

Density-gradient mechanism of vortex plastic creep

The electromagnetic response of type-II superconductors exposed to a magnetic field is governed by the dynamics of the vortex matter. We found that there exists a force of non-Peach-K\"ohler type which acts on edge dislocations in vortex lattices and depends on the gradients of vortex density. This force is absent in atomic solids where the density of the crystal lattice is constant even in the presence of dislocations. By mapping the classic theory of dislocations onto vortex lattices, we find the critical current ${j}_{c}^{\text{pl}}$ and the activation energy ${U}_{\text{pl}}$ associated with the dislocation-mediated plastic creep. The latter proves to decrease with magnetic field as ${B}^{\ensuremath{-}3/4}$, in concordance with experimental data. Such behavior of ${U}_{\text{pl}}$ is just opposite to the case of elastic (collective) creep, where ${U}_{\text{el}}$ always grows with $B$. At high enough field ${U}_{\text{pl}}$ becomes less than ${U}_{\text{el}}$, thus plastic creep overwhelms the elastic one and becomes the dominant mechanism of vortex mobility. This explains the appearance of the ``fishtail'' (double-peak) shape of magnetization curves in high-${T}_{c}$ superconductors.

Dislocation-mediated and twinning-induced plasticity of CoCrFeMnNi in varying tribological loading scenarios

Coarse-grained, metallic materials undergo microstructure refinement during tribological loading. This in turn results in changing tribological properties, so the microstructural evolution is a parameter which should not be underestimated while designing tribological systems. Single-trace experiments were conducted to understand the initiation of deformation mechanisms acting in various tribological systems. The main scope of this work was to investigate the influence of normal and friction forces as well as crystal orientations on the dominating deformation mechanism in a face-centred cubic concentrated solid solution. While varying the normal force is easily realised, varying friction forces were achieved by using several counter body materials paired against CoCrFeMnNi. The subsurface deformation layer was either mediated through dislocation slip or twinning, depending on the grain orientation and on the tribological system. A layer dominated by dislocation-based deformation is characterised by lattice rotation, the formation of a dislocation trace line or subgrain formation. Such behaviour is observed for tribological systems with a low friction coefficient. For systems dominated by deformation twinning, three types of twin appearance were observed: small twins interacting with the surface, large twins and grains with two active twin systems. Two different twinning mechanisms are discussed as responsible for these characteristics.Graphical abstract

Influence of microstructural deformation mechanisms and shear strain localisations on small fatigue crack growth in ferritic stainless steel

Microstructurally small fatigue crack growth (FCG) rate in body-centred cubic (BCC) ferritic stainless steel is investigated by using a novel domain misorientation approach for EBSD microstructural deformation analyses, in conjunction with in situ digital imaging correlation (DIC). The DIC analyses revealed that shear strain localisations occur ahead of the crack tip during propagation and correlate well with the FCG rate retardations. Grain boundaries can be found at both peaks and valleys of the FCG rate curve and alter the interaction between crack growth and shear strain localisations. At the microstructural level, the deformation is associated with the dislocation-mediated plastic deformation process, showing increased formation of grain sub-structures in the regions of the strain localisation. Consequently, material experiences local hardening causing the FCG retardation events. If the crack avoids the hardened material region through a macroscopic cross-slip mechanism, retardation is minor. On the contrary, if the crack penetrates the hardened region, retardation is significant.

Effect of solid-solution strengthening on deformation mechanisms and strain hardening in medium-entropy V1-Cr CoNi alloys

• The solid-solution strength linearly increases with v in V 1- x Cr x CoNi alloys. • Addition of v highly increases SFE and induces planar slip behavior. • The V -abundant VCrCoNi alloys exhibit higher strain-hardening than TWIP CrCoNi alloy. • High friction stress is predominant than SFE in determining deformation mechanism. • High friction stress lowers cross-slip activation and dislocation annhiliation rate. High- and medium-entropy alloys (HEAs and MEAs) possess high solid-solution strength. Numerous investigations have been conducted on its impact on yield strength, however, there are limited reports regarding the relation between solid-solution strengthening and strain-hardening rate. In addition, no attempt has been made to account for the dislocation-mediated plasticity; most works focused on twinning- or transformation-induced plasticity (TWIP or TRIP). In this work we reveal the role of solid-solution strengthening on the strain-hardening rate via systematically investigating evolutions of deformation structures by controlling the Cr/V ratio in prototypical V 1- x Cr x CoNi alloys. Comparing the TWIP of CrCoNi with the dislocation slip of V 0.4 Cr 0.6 CoNi, the hardening rate of CrCoNi was superior to slip-band refinements of V 0.4 Cr 0.6 CoNi due to the dynamic Hall-Petch effect. However, as V content increased further to V 0.7 Cr 0.3 CoNi and VCoNi, their rate of slip-band refinement in V 0.7 Cr 0.3 CoNi and VCoNi with high solid-solution strength surpassed that of CrCoNi. Although it is generally accepted in conventional alloys that deformation twinning results in a higher strain-hardening rate than dislocation-mediated plasticity, we observed that the latter can be predominant in the former under an activated huge solid-solution strengthening effect. The high solid-solution strength lowered the cross-slip activation and consequently retarded the dislocation rearrangement rate, i.e., the dynamic recovery. This delay in the hardening rate decrease, therefore, increased the strain-hardening rate, results in an overall higher strain-hardening rate of V -rich alloys.