Underlying Deformation Mechanisms Research Articles

Strength of nano-twinned gradient nano-grained copper: Molecular dynamic simulation

Molecular dynamics simulations are performed to reveal the underlying deformation mechanisms of gradient nano-grained materials with different-sized twins. The results indicate that the critical twin boundary spacing where the strength begins to soften decreases and the maximum strength of the material increases with the declining of the gradient. Below the critical value, the plastic deformation mechanism is dominated by the partial dislocations paralleling to the twin boundary, but when the twin boundary spacing exceed the critical value, the dislocation moved by the way of intersecting to the twin boundary.

Twin-boundary-spacing-dependent strength in gradient nano-grained copper

Twin boundaries acting as efficient barriers for dislocation propagation can significantly improve the strength of conventional polycrystalline materials, which peaks at a critical value. Whether such a critical value also exists in heterostructured materials is poorly understood. In this study, molecular dynamics simulations are performed to reveal the underlying deformation mechanisms of gradient nano-grained materials with different-sized twins. The results indicate that the critical twin boundary spacing where the strength begins to soften decreases and the maximum strength of the material increases with the declining of the gradient. The plastic deformation mechanism below the critical value is dominated by the nucleation and emission of twinning partial dislocations parallel to the twin boundary at the intersections of twin and grain boundaries. The high-density twin boundary spacing destabilizes the grain boundary architecture, resulting in a decline in strength.

Investigation of dynamic impact responses of layered polymer-graphene nanocomposite films using coarse-grained molecular dynamics simulations

Polymer nanocomposite films have recently shown superior energy dissipation capability by using the micro-projectile impact testing method. However, how stress waves interact with nanointerfaces and the underlying deformation mechanisms have remained largely elusive. This paper investigates the detailed stress wave propagation process and dynamic failure mechanisms of layered poly(methyl methacrylate) (PMMA)-graphene nanocomposite films during piston impact through coarse-grained molecular dynamics simulations. The spatiotemporal contours of stress and local density clearly demonstrate shock front, reflected wave, and release wave. By plotting shock front velocity (Us) against piston velocity (Up), we find that the linear Hugoniot Us−Up relationship generally observed for bulk polymer systems also applies to the layered nanocomposite system. When the piston reaches a critical velocity, PMMA crazing can emerge at the location where the major reflected wave and release wave meet. We show that the activation of PMMA crazing significantly enhances the energy dissipation ratio of the nanocomposite films, defined as the ratio between the dissipated energy through irreversible deformation and the input energy. The ratio maximizes at the critical Up when the PMMA crazing emerges and then decreases as Up further increases. We also find that a critical PMMA-graphene interfacial strength is required to activate PMMA crazing instead of interfacial separation. Additionally, layer thickness affects the amounts of input energy and dissipated energy for nanocomposite films under impact. This study provides important insights into the detailed dynamic deformation mechanisms and how nanointerfaces/nanostructures affect the energy dissipation capability of layered nanocomposite films.

Molecular dynamics simulation on creep-ratcheting behavior of columnar nanocrystalline aluminum

Creep-ratcheting deformation behavior of columnar nanocrystalline (NC) Al varying in grain sizes have been studied using molecular dynamics simulations at three different temperatures (300 K, 467 K, and 653 K). The underlying deformation mechanisms of columnar NC Al for two stress ratios of ratcheting are also evaluated in this study. The highest strain accumulation and rapid hysteresis loop proliferation are attained at 653 K. The dislocation density is low at 653 K in contrast to the other two deformation temperatures. The perfect dislocations support the creep-deformation process followed by Shockley partial dislocations. It is observed that the cyclic hardening phenomenon at 300 K and the cyclic softening phenomenon at 653 K dominate during creep-ratcheting loading. The specimen fails earlier at higher temperatures owing to the change in the shape of hysteresis loops. The predominant grain boundary-based deformation mechanisms of columnar NC Al specimens are grain boundary (GB) migration, GB diffusion, GB widening, GB sliding, and GBs merging for all the deformation temperatures. The variation in the extent of deformation with respect to temperatures depends on strain accumulation in the plastic region under creep-ratcheting loading.

Ductilizing Ti19Zr19Hf19Nb19TM5Be19 (TM = Fe, Co, Ni and Cu) high-entropy bulk metallic glass composites via in-situ precipitated refractory high-entropy alloy dendrites

In this work, a series of Ti19Zr19Hf19Nb19TM5Be19 (at.%, TM = Fe, Co, Ni and Cu) high-entropy bulk metallic glass composites (HE-BMGCs) were successfully developed to address the absence of tensile ductility in high-entropy bulk metallic glasses (HE-BMGs). It is shown that the mechanical properties of HE-BMGCs are jointly affected by the two constituent phases of refractory high-entropy alloy (RHEA) dendrites and HE-BMG matrix. The present composites show that the good tensile ductility as well as excellent work-hardening capability at ambient temperature. Based on the post-deformation microstructure and theoretical analyses, cross slips dominate the deformation mechanism of HE-BMGCs, and it is found that the dislocation multiplication mechanism composed of dislocation pinning and double cross-slip is very prevalent in current composites. Therein, the dislocation multiplication of RHEA dendrites facilitates the inhibition and retardation to the propagation of shear bands in the HE-BMG matrix, which is responsible for the good tensile ductility of HE-BMGCs. Additionally, the excellent work-hardening capability of composites is attribute to severe dislocation interactions caused by intrinsic local-regional multicomponent fluctuations and dislocation cross-slips in RHEA dendrites. Our research results not only aid in understanding the underlying deformation mechanism of HE-BMGCs, but also offer a novel perspective for designing the ductile high-entropy dual-phase alloys.

Bifunctional Metamaterials Incorporating Unusual Geminations of Poisson's Ratio and Coefficient of Thermal Expansion.

Natural materials overwhelmingly shrink laterally under stretching and expand upon heating. Through incorporating Poisson's ratio and coefficient of thermal expansion (PR and CTE) in unusual geminations, such as positive PR and negative CTE, negative PR and positive CTE, and even zero PR and zero CTE, bifunctional metamaterials would generate attractive shape control capacity. However, reported bifunctional metamaterials are only theoretically constructed by simple skeletal ribs, and the magnitudes of the bifunctions are still in quite narrow ranges. Here, we propose a methodology for generating novel bifunctional metamaterials consisting of engineering polymers. From concept to refinement, the topology and shape optimization are integrated for programmatically designing bifunctional metamaterials in various germinations of the PR and CTE. The underlying deformation mechanisms of the obtained bifunctions are distinctly revealed. All of the designs with complex architectures and material layouts are fabricated using the multimaterial additive manufacturing, and their effective properties are experimentally characterized. Good agreements of the design, simulation, and experiments are achieved. Especially, the accessible range of the bifunction, namely, PR and CTE, is remarkably enlarged nearly 4 times. These developed approaches open an avenue to explore the bifunctional metamaterials, which are the basis of myriad mechanical- and temperature-sensitive devices, e.g., morphing structures and high-precision components of the sensors/actuators in aerospace and electronical domains.

Origin, parameters, and underlying deformation mechanisms of propagating deformation bands in irradiated 316L stainless steel

Lüders-type propagating deformation bands were observed in specimens of irradiated 316L stainless steel samples removed from Spallation Neutron Source target vessels after service. Mechanical testing with digital image correlation (DIC) and in-situ tensile testing with scanning electron microscopy electron backscatter diffraction showed that the observed Lüders-type behavior was not related to the known transformation-induced plasticity or twinning-induced plasticity behavior. Instead, the phenomenon occurs at small local strain values before a significant amount of martensite or deformation twins appear in the microstructure. Microstructural analysis and in-situ mechanical test results suggest Lüders-type band formation and propagation were related to the appearance and evolution of defect-free channels—analogous to slip bands. A modified Swift equation with a Ludwigson-like component was offered to rationalize the phenomenon and model the strain-softening processes at small strain values. The results indicate complex microstructural processes and deformation mechanisms were active at small strain values and underline the benefits of advanced mechanical test approaches such as DIC.

Complex dynamic restoration processes leading to a high degree of deformability in a dual-phase Al0.5CoCrFeNi high entropy alloy

The current research provides scientific evidence based on experimental and modeling approaches that complex softening processes characterized by dynamic recovery (DRV) and dynamic recrystallization (DRX) combined with twinning contribute efficiently to the hot deformation processing of the Al 0.5 CoCrFeNi alloy. An as-cast face-centered-cubic (fcc) oriented Al 0.5 CoCrFeNi dual-phase high entropy alloy, HEA, was deformed in uniaxial compression to a true strain 0.8 at temperatures between 900 and 1100 ºC and strain rates from 0.0013 to 0.1 s −1 . A dynamic material model was applied to predict the processing windows, and the underlying deformation mechanisms were characterized using scanning electron microscopy and electron backscattered diffraction. The optimum processing window for the studied alloy is at 900–960 ºC/ 0.0013–0.002 s −1 , where the efficiency of power dissipation and strain rate sensitivity ranges from 45% to 50% and 0.28–0.33, respectively. The processing map also exhibits a domain of flow instability located in the lower temperature and higher strain rate regions, resulting mainly from flow localization. The studied alloy represents a dual-phase fcc + bcc/B2 microstructure in an as-cast (undeformed) state. The fcc matrix occupying 94 vol% forms dendrites with an average diameter of 210 µm, decorated by discrete networks of bcc/B2 phase of average grain size 3.5 µm residing in interdendritic regions. The microstructural analyses corroborate the coincidence of DRX and twinning in the fcc phase in all deformed specimens. However, only DRV takes place within the bcc phase. The current study reveals a well-suited parameter range to achieve a high degree of hot deformability in dual-phase HEAs by taking advantage of twinning combined DRX to refine the microstructure significantly. Future work will have to identify possible application cases. • The possibility of hot deformation processing of a duplex fcc+bcc Al 0.5 CoCrFeNi alloy. • Complex dynamic restoration processes lead to a high degree of hot workability. • The optimum processing window locates at 900–960 ºC/ 0.0013–0.002 s −1 . • Shear localization yields flow instability in lower temperature and higher strain rate regions.

Influence of ageing on high temperature tensile deformation of a Ni-based superalloy, HAYNES 282

The effect of ageing time and temperature on the deformation mechanism and corresponding tensile properties are investigated in a γ/γ′ Ni-based superalloy, HAYNES 282. Through a systematic variation in duration (24 h and 216 h) and temperature of ageing (650 °C and 760 °C), a significant variation in strengthening microstructural features was achieved in the resulting microstructures. While in one case (650 °C, 24 h ageing condition), a microstructure with no γ′ was observed, for the rest of the cases, γ′ precipitates of varied sizes were observed. In one specific case (760 °C, 216 h ageing condition), very fine (4–6 nm) MC carbides were observed along with γ′ precipitates; in which these tiny MC carbides became the deciding factor for strength over γ′ precipitates. While common knowledge of smaller γ′ precipitates giving higher strength could explain the higher strength at 760 °C, 24 h ageing condition as compared to 650 °C, 216 h ageing condition, the further increase in strength in case of 760 °C, 216 h ageing condition, even with much larger γ′ precipitates was something quite interesting and counterintuitive. This paper elucidates this puzzling observation. The variation of tensile properties of these wide varieties of microstructures will be described in this paper in light of the underlying deformation mechanisms. A change in deformation mechanism from planar slip (microstructure with no γ′) to twinning (microstructure with γ′) and Orowan-looping (microstructure with γ′ along with fine nano carbides) as a function of microstructure explains the difference in strength, ductility, and strain hardening phenomena among the varied ageing conditions.

Near-Net Shape Manufacture of Ultra-High Strength Maraging Steel Using Flow Forming and Inertia Friction Welding: Experimental and Microstructural Characterization

Abstract Flow forming and inertia friction welding (IFW) have been widely used as manufacturing processes that produce high-value engineering components. Combining these two advanced processes facilitates the fabrication of near-net shape components leading to optimized designs. This study introduces the joining of flow-formed seamless tubes of MLX®19 maraging steel using the IFW process to fabricate a near-net shape component used in landing gears and missile parts. The as-received material was initially provided ≈30% reduction in thickness from the flow forming trials and then welded at four varying weld energies while maintaining constant friction and forge pressures. The mechanical behavior of the weldments was characterized, and the optimized weld parameters were determined. The concomitant microstructural evolution of the optimized weld was also examined to comprehend the underlying deformation mechanisms. The weld strength, axial shortening, and width of dynamic recrystallization (DRX) displayed an increasing trend with an increase in the weld energy. The weld-zone (WZ) and thermomechanical affected zone (TMAZ) showed the presence of martensite, whereas in the HAZ presence of intermetallic precipitates and reverted austenite was confirmed along with tempered martensite. Based on microstructural evidence, it was concluded that the peak temperature attained in the WZ was above Ac3, whereas in the TMAZ it was in-between Ac1 and Ac3. The evolution of crystallographic texture implied that WZ was subjected to pure shear deformation during the welding whereas the TMAZ experienced a combined shear and compressive deformation.

Mechanical Properties and Deformation Behavior of Superhard Lightweight Nanocrystalline Ceramics.

Lightweight polycrystalline ceramics possess promising physical, chemical, and mechanical properties, which can be used in a variety of important structural applications. However, these ceramics with coarse-grained structures are brittle and have low fracture toughness due to their rigid covalent bonding (more often consisting of high-angle grain boundaries) that can cause catastrophic failures. Nanocrystalline ceramics with soft interface phases or disordered structures at grain boundaries have been demonstrated to enhance their mechanical properties, such as strength, toughness, and ductility, significantly. In this review, the underlying deformation mechanisms that are contributing to the enhanced mechanical properties of superhard nanocrystalline ceramics, particularly in boron carbide and silicon carbide, are elucidated using state-of-the-art transmission electron microscopy and first-principles simulations. The observations on these superhard ceramics revealed that grain boundary sliding induced amorphization can effectively accommodate local deformation, leading to an outstanding combination of mechanical properties.

Heterogeneous microstructure of duplex multilayer steel structure fabricated by wire and arc additive manufacturing

Wire and arc additive manufacturing (WAAM) is suitable for fabricating multimaterial dense structures in various additive manufacturing technologies. Watanabe et al. [1] reported that a unique two-stage stress–strain curve was observed during tensile testing of a duplex multilayer steel structure fabricated by WAAM. The material behavior was explained by the transformation-induced plasticity, which was attributed to a decrease in the austenite phase observed after testing using X-ray diffraction at three representative points of the tensile test specimen. However, the deformation mechanism was unclear from the viewpoint of the composite structure mechanics. In this study, the heterogeneous microstructure of the steel structure was investigated for the duplex layer region to infer the relationship between the material response and underlying deformation mechanism. The distributions of the phase and major alloy elements indicated that the layers melted and mixed during WAAM, and the multilayer structure subsequently changed compared to the design layout. The WAAM structure was composed of two dual-phase layers containing different volume fractions of the martensite phase. Hence, the austenite phase in the martensite-rich layer initially deformed and then transformed to the martensite phase during tensile testing. Consequently, the strength of the martensite-rich layer was recovered to the micromechanically estimated level and the two-stage stress–strain curve was generated. Thus, this paper presents the potential of multimaterial WAAM for controlling microscopic heterogeneities and their material responses by adjustment of the process parameters. • Unique two-stage stress–strain curve obtained from WAAM duplex multilayer structure. • Deformation mechanisms investigated from microscopic heterogeneities viewpoint. • The multilayer structure differs from the design layout because of melt–mixing. • Strain-induced transformation in martensite-rich layer led to two-stage response.

Impact of the Atomic Packing Density on the Properties of Nitrogen-Rich Calcium Silicate Oxynitride Glasses.

In this work, the impact of the atomic packing density/fractional glass compactness of Ca–Si–O–N glasses on glass transition and crystallization temperatures, glass density, microhardness, molar volume, and refractive index were examined. It was found that the atomic packing density increased with increasing the nitrogen content and decreased with increasing the Ca content in the glass network. Furthermore, density, glass transition and crystallization temperatures, and refractive index, increased with an increasing atomic packing density of the glass, while molar volume increased with decreasing atomic packing density values. The change in hardness with atomic packing density is less clear and suggests that the atomic packing density does not solely control the underlying deformation mechanism. There is indeed competition between densification (favored at low packing density values) and isochoric shear (at larger packing density). Despite that, the effects of nitrogen as a network former and Ca as a modifier are significantly independent. The obtained results indicate that the atomic packing density of the prepared samples linearly depends on many mechanical and optical properties, suggesting that the glass network and cross-linking are proportional to the ionic radius of the Ca and the nitrogen content, respectively.

Unraveling the temperature-dependent plastic deformation mechanisms of polycrystalline Ta implants through numerical analysis of grain boundary dynamics

Nanostructured tantalum (Ta)-based dental implants have recently attracted significant attention thanks to their superior biocompatibility and bioactivity as compared to their titanium-based counterparts. While the biological and chemical aspects of Ta implants have been widely studied, their mechanical features have been investigated more rarely. Additionally, the mechanical behavior of these implants and, more importantly, their plastic deformation mechanisms are still not fully understood. Accordingly, in the current research, molecular dynamics simulation as a powerful tool for probing the atomic-scale phenomena is utilized to explore the microstructural evolution of pure polycrystalline Ta samples under tensile loading conditions. Various samples with an average grain size of 2–10 nm are systematically examined using various crystal structure analysis tools to determine the underlying deformation mechanisms. The results reveal that for the samples with an average grain size larger than 8 nm, twinning and dislocation slip are the main sources of any plasticity induced within the sample. For finer-grained samples, the activity of grain boundaries—including grain elongation, rotation, migration, and sliding—are the most important mechanisms governing the plastic deformation. Finally, the temperature-dependent Hall–Petch breakdown is thoroughly examined for the nanocrystalline samples via identification of the grain boundary dynamics.

A strong, ductile and in-plane tensile isotropic Mg-0.5Zn-0.5Y-0.15Si alloy

Strength ductility tradeoff, strain hardenability and in-plane isotropy under tensile loading are big dilemmas in magnesium alloys. In this study, we have fabricated an extruded low alloyed Mg-0.5Zn-0.5Y-0.15Si alloy. Based on bimodal grain size, strong basal texture, Schmidt factor analysis and precipitates (MgZn2, Mg3Zn6Y and Mg3Zn3Y2), the alloy exhibited high mechanical strength, high elongation to fracture, strain hardenability and excellent in-plane tensile isotropy. The underlying deformation mechanisms for excellent symmetric and high yield strength along extruded and transverse directions were synergistic effects of low Schmidt factor values of <a> basal slip due to intense basal texture (c-axes//ND), pre-induce dislocation, grain boundary strengthening and precipitate strengthening. While, the strain hardenability and high elongation to fracture are the combined effect of the interaction of <a> basal and profuse non-basal <c+a> dislocation with precipitates, dislocation pileup at grain boundaries, dislocation pileup on stacking faults and the signature of extension and contraction twinning activity.

Atomic level simulations of the phase stability and stacking fault energy of FeCoCrMnSi high entropy alloy

High entropy alloys (HEAs) have many promising properties beneficial to advanced technologies. However, their underlying deformation mechanisms are largely unclear. So, as a first step, we have developed a modified embedded atom method potential for FeCoCrMnSi alloys to study such mechanisms. We predict the phase stability, chemical short-range ordering (CSRO), and stacking fault energy (SFE) of a specific alloy system using molecular dynamics (MD) and hybrid Monte-Carlo and molecular dynamics (MC/MD) simulation techniques. Room temperature MD simulations showed that both the potential energy and free energy of the single phase ε-hcp alloy is marginally more stable than the γ-fcc phase alloy, which resulted in a large, negative SFE. However, the room temperature MC/MD simulation showed an opposite trend where the γ-fcc phase was found to be more stable than the ε-hcp phase, and this resulted in a small, positive SFE. The prediction of the lower energy γ-fcc phase and resultant SFE agreed well with the experimentally reported SFE and phase stability for the Fe40Co20Cr15Mn20Si5 HEA, illustrating the importance of CSRO. Also, the calculated basal SFE of the hcp phase was close to that of the fcc phase. Therefore, the MC/MD implementation is crucial for the proper prediction of the phase stability and structural evolution in this HEA system. Many previous studies showed the ability of hybrid MC/MD technique to obtain consistent structural and configurational information of different alloy systems. The current work illustrates the potential of accelerating HEA materials development by utilizing computational methods based on the MC/MD technique which can reduce time and cost associated with experimental methods.

Atomistic insights on the deformation mechanisms of Cox(CrNi)100-x multicomponent alloys: The effect of Co content

CoCrNi multicomponent alloys with equiatomic and non-equiatomic concentrations are promising for achieving an excellent balance of strength and ductility. However, the correlations between elemental concentrations and deformation mechanisms of this alloy family need to be uncovered for further targeted alloy design. In this work, atomistic molecular dynamics simulations were performed to study the effects of Co concentration on the mechanical behaviors and underlying deformation mechanisms of single-crystal Cox(CrNi)100-x (x = 13, 23, 33.3, 50 at. %) alloys. Atomic-scale microstructural evolution with increasing the compressive strain was revealed in each specimen with different Co concentrations. The results suggest that the yield stress and elastic modulus are enhanced with increasing the Co content. Atomic pairs containing Cr exhibit the lowest cohesion energy among all pair types, and therefore Cr atoms participate most actively in dislocation nucleation. Although dislocation slip comes into play in all specimens, the primary deformation mechanism changes from the multilayering of stacking faults (SFs) to the formation of primary-secondary twin pairs with the increase of Co content. Further, the twinnability of these alloys was estimated using a theoretical model based on the generalized stacking fault energy (GSFE) curves. The results indicate that the Co50Cr25Ni25 alloy owns the highest twinning tendency among the probed alloy variants, which promotes the formation of secondary deformation twins and leads to high deformability. This work provides guidelines for the design of non-equiatomic CoCrNi multicomponent alloys with proper Co content for desirable mechanical properties.

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Traditional metallic materials usually face a dilemma between high strength and poor strain hardening capacity. However, heterogeneous structured metallic materials have been found to obviously overcome the trade-off. Herein, gradient lamellar structure was fabricated through ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat treatment. The gradient lamellar Ni was successively divided into the four regions. In-situ micropillar compression tests were conducted in different regions to reveal the corresponding microscopic mechanical properties. Microscopic characterization techniques were performed to explore underlying deformation mechanisms and the effects of microstructural parameters on deformation behaviors. This work demonstrates that the micropillar with near nanoscale lamellar thickness possesses excellent strength and plasticity. On one hand, the reason for high strength of near nanoscale micropillar is that the strength of micropillar increases with the decrease of lamellar thickness according to the Hall-Petch effect. On the other hand, numerous lamellar grain boundaries perpendicular to the loading direction is found to hinder the motion of slip bands, resulting in great strain hardening capacity in the near nanoscale lamellar micropillar.

A novel enhanced anti-tetra-missing rib auxetic structure with tailorable in-plane mechanical properties

In analogy with the enhanced hexa-missing rib structure, a novel enhanced anti- tetra-missing rib structure was proposed in this work. Using a simple energy-based approach, mechanical modelling under infinitesimal deformation was proposed to provide guidelines for determining the geometries with targeted mechanical properties. It is shown that the proposed structure provides tunable Poisson’s ratios and elastic and shear moduli in wide ranges. The analytic solutions of the effective Poisson’s ratio, elastic and shear moduli from the mechanics model were validated by systematic finite element (FE) calculations on one unit-cell with considering periodic boundary conditions (PBCs). The underlying deformation mechanism accounting for the auxetic behavior on different geometric parameters of the proposed design was then investigated by elaborated FE analysis in a large deformation regime. The targeted NPR performance was also verified with a nonlinear base material. Uniaxial tensile experiments and the corresponding numerical simulations for lattice structures consisting of an array of proposed unit-cells were also performed to validate the theoretical and FE results obtained from one unit-cell analysis.

Dynamic compressive properties and microstructural evolution of Al1.19Co2CrFeNi1.81 eutectic high entropy alloy at room and cryogenic temperatures

The development of aerospace and military defense sectors has put forward higher requirements for the mechanical properties of metals under extreme conditions. Eutectic high entropy alloys (EHEAs) show a wide potential application in these fields due to their superior mechanical performances and good castability. Here, we systematically investigated the dynamic compressive properties and microstructural characteristics of the Al1.19Co2CrFeNi1.81 EHEA at room temperature (298 K) and liquid nitrogen temperature (77 K). The EHEA exhibits an excellent strength-plasticity combination, especially at the strain rate of 4300 s−1 at 77 K, showing a yield strength of 1365 MPa and a true plastic strain over 40%. The underlying deformation mechanisms were uncovered using transmission electron microscopy, revealing that the deformation mechanism is dominated by dislocation slip at 298 K. However, at 77 K, nanotwins together with dislocation slip dominate the plastic deformation. Meanwhile, profuse relatively stable structures are formed due to the interactions between stacking fault (SF)-SF, dislocation-twin boundary and nanotwin-nanotwin, which can effectively inhibit dislocation movement and contribute to a superior strain hardening ability. The adiabatic shear band forms in the late stage of dynamic deformation, and the fractographic observations show a transition from ductile to mixed ductile–brittle fracture mode with decreasing temperature.