Metastable high-entropy alloys can exhibit coupled phase transformation, strain localization and damage evolution under shock loading, and their spall responses are governed by both the loading intensity and the duration of the stress pulse. To clarify the distinct roles of impact velocity and pulse duration in spallation behavior and void evolution, plate-impact experiments were conducted on a Si₄V₅Mn₅Cr₁₀Co₃₀Fe₄₆ metastable high-entropy alloy using a single-stage light-gas gun. The free-surface velocity response, spall parameters, local microstructural evolution and three-dimensional void morphology under different loading conditions were systematically investigated. The results show that, at a fixed specimen thickness, increasing the impact velocity from 282 m/s to 553 m/s markedly raises the peak free-surface response and the peak compressive stress, whereas the spall strength only slightly changes. Meanwhile, internal voids evolve from dispersed nucleation to localized clustering, accompanied by increased fractions of HCP/BCC (hexagonal close-packed/body-centered cubic) phases and a pronounced rise in high-KAM (kernel average misorientation) regions near the voids, suggesting that higher impact velocity promotes local phase transformation, lattice distortion and concentrated damage development. Micro-X-ray computed tomography further reveals that increasing impact velocity drives the voids towards larger volumes, stronger spatial concentration and more complex morphologies. In contrast, under nearly constant impact velocity, as the specimen thickness increases from 1.0 mm to 2.0 mm, the pulse duration is prolonged from 0.075 μs to 0.250 μs, and the spall strength correspondingly increases from 1.40 GPa to 1.83 GPa. The spatial distribution of voids gradually changes from dispersed to centrally concentrated, with an enhanced tendency for interconnection, indicating that longer pulse duration demonstrates greater favorability towards damage accumulation and localized coalescence. By combining free-surface velocity histories, two-dimensional microstructural characterization and three-dimensional void statistics, it is shown that the impact velocity mainly controls the instantaneous driving force for the damage during spallation, whereas the pulse duration primarily governs the time window for the damage accumulation and the extent of localization. Together, these two factors determine the nucleation sites, growth paths and final failure mode of spall damage in this metastable high-entropy alloy.

High-entropy carbides (HECs), which are characterized by pronounced chemical disorder and lattice distortion, exhibit exceptional strength-toughness synergy and are promising candidates for impact protection and high-temperature structural applications. However, their microstructural evolution and stress response under extreme conditions, such as high stress and strain rates, remains poorly understood. In this work, a high-accuracy machine-learning interatomic potential is employed to investigate the representative multi-principal carbide (Zr_0.2Hf_0.2Ti_0.2Nb_0.2Ta_0.2)C (HEC) through large-scale molecular dynamics (MD) simulations. To elucidate how multiple “high-entropy” effects govern atomic-scale plasticity in HECs, large-scale MD simulations are carried out to explore their response under quasi-isentropic compression and ramp-wave loading along three principal crystallographic orientations: [001], $ [01\overline{1}] $, and [111]. The results demonstrate that the high-entropy effects profoundly reshape the initiation of plasticity, the competition among slip systems, and the localized deformation modes in HEC. Local stress fluctuations and lattice distortions enhance transient Bain-type stacking rearrangements within the sublattice and promote the synergistic activation of multiple slip systems. This leads to a transformation of shear band formation from isolated nucleation to a network-like propagation. Complementary first-principles calculations reveal that the carbon vacancy formation energy in high-entropy ceramics is significantly reduced compared to their single-component carbides. This reduction of vacancy formation energy facilitates preferential displacement of carbon atoms and their participation in shear band nucleation during compression. Furthermore, the comparison between different loading paths highlights the complexity of the high-entropy effects’ response. The quasi-isentropic loading path helps to unveil the intrinsic deformation mechanisms governed by the high-entropy effect itself, whereas the stress gradients inherent in ramp-wave loading couple with the high-entropy effect, leading to a premature triggering and intensification of plastic localization.

Micro-jetting and micro-spallation at metal interfaces under intense shock loading play pivotal roles in applications such as inertial confinement fusion (ICF). These phenomena exhibit inherent complexity due to their multi-scale dynamics, strong nonlinearity, and coupled multi-field interactions. Under extreme irradiation conditions, the formation of high-pressure nanoscale helium bubbles significantly alters interface failure mechanisms. Using molecular dynamics methods, we investigate micro-jet growth and damage evolution in helium-containing copper subjected to double supported shock loadings. Helium bubbles demonstrate lower critical activation stress thresholds for expansion compared to void nucleation, with these thresholds being dependent on bubble distribution and number density. Under low-pressure primary shocks, helium-containing metals produce more pronounced micro-jets than pure metals. During secondary shocks, helium bubbles promote jet fragmentation, resulting in higher maximum velocities at micro-jet tips while maintaining comparable velocity distributions in micro-jet bodies. Secondary shocks show negligible effects on bulk helium bubbles that were previously compressed by initial shocks and partially rebounded due to rarefaction waves without complete recovery. Near-surface ruptured bubble walls may reattach to bubble bases after secondary shocks, temporarily re-trapping helium atoms that are subsequently released during unloading-induced re-expansion and rupture. The collapse mechanism of helium bubbles under secondary shock is closely related to the helium bubbles size and the strength of secondary shock. This study establishes fundamental physical understanding and provides a theoretical foundation for future cross-scale investigations of coupled micro-jetting and micro-spallation evolution in irradiated helium-containing metals.

Grain size effect is one of the key factors governing the dynamic mechanical response of metallic materials. Phase transformation iron is selected as the model material, and a series of nanocrystalline polycrystals with identical topology and grain orientation distributions but different grain sizes are constructed to investigate size effects under a fixed grain configuration. Molecular dynamics simulations show that, under high strain rate uniaxial compression, all models undergo elastic deformation, α→ε phase transition, and high-pressure phase plastic deformation. During the elastic stage, grain boundaries act as a soft layer, leading to lower stresses in the fine grain models than in the coarse grain model. After the structural phase transition, grain boundaries hinder the plastic development of the new phase, so that the fine grain models exhibit higher stress than the coarse grain models. At the onset of phase transition, the threshold of phase transition of smaller grains is lower, and the transformed phase in fine grains mainly forms stacking fault structures, whereas twinning structures appear in relatively larger grains. With increasing strain, the disappearance of twinning and the reconstruction of stacking faults are observed in large grains. Under high strain rate tension, shear strain of grain boundary in the large grain models is highly localized, readily forming continuous shear bands that serve as preferred paths of crack propagation. After grain refinement, shear strain of grain boundary gradually evolves into a diffuse mode, and the effective paths of crack propagation are constrained by the network of grain boundaries. The change of grain boundary effects leads to a non-monotonic variation of fracture strength with the grain size.

This work integrates stochastic theory with a phase-field model for spallation in ductile metals. By assigning four distinct random distributions to the initial yield strength to characterize the random distribution of material defects and employing an explicit dynamic solver, the entire process of spall damage—from gradual evolution to instability and coalescence—was successfully simulated. The simulation results were validated through plate impact experiments and triangular wave loading experiments. These validations revealed the relationship between the heterogeneity of material yield strength and both the spall strength and the number/area of damaged zones. The results indicate a negative correlation between the standard deviation of the initial yield strength and the spall strength, which holds for both single and multiple spall scenarios in ductile metals. For single spallation, regardless of the initial distribution of yield strength, the resulting spall strength follows a normal distribution. For multiple spallation, the number of initially nucleated damaged zones increases linearly with the standard deviation, while the size of these zones follows a Weibull distribution. Under the same initial random distribution, the number of damaged zones evolves over time, showing a trend of initial slow growth, subsequent acceleration until saturation, and a final decline after saturation. This trend corresponds to the typical process of damage evolution involving nucleation and coalescence during spallation.

This study systematically investigated the effects of temperature on the spall behavior of Invar36 alloy through plate impact experiments and microstructural characterization techniques. Utilizing a single-stage light gas gun loading platform combined with a high-temperature heating device, the experiments measured free surface velocity profiles and spall strength variations in samples with different segregation orientations within the temperature range of 20 ℃ to 300 ℃. Results demonstrate that the spall strength of Invar36 alloy exhibits a linear decrease with increasing temperature, with elevated temperatures significantly weakening its dynamic tensile resistance. Microstructural damage analysis reveals that at room temperature, voids nucleate and propagate along element segregation bands, while high-temperature damage concentrates at grain boundaries. Elevated temperatures reduce the constraining effect of segregation and facilitate material softening through thermally activated dislocation motion. The research elucidates the central role of temperature in governing spall strength and damage mechanisms, providing a theoretical foundation for failure-resistant design of Invar36 alloys under high-temperature impact conditions.

Obtaining the mechanical response of CuCrZr alloy under coupled electro-magnetic-thermal-mechanical loading is significant for the engineering application of CuCrZr alloy, which is one of the candidate materials for electromagnetic railgun rails. This paper proposes an external-magnetic-field-assisted electromagnetic expanding ring technique, which stably achieves high strain rate loading exceeding 10⁴ s^–1 without the significant increase in the induced current and Joule heating temperature rise in the metal sample ring. Based on this technique, a study on the dynamic tensile properties of CuCrZr alloy under coupled electro-magnetic-thermal-mechanical loading was conducted. The stress-strain curves and fracture strain of CuCrZr alloy under conditions of high current density, high strain rate, high temperature rise rate, and strong magnetic field were obtained. The results provide important references for the application of CuCrZr alloy under multi-physics field coupling conditions.

The continuous advancement of modern armor protection technology has imposed severe challenges on the damage power of shaped charge warheads. Traditional liner materials have become a major constraint in improving penetration depth due to their limited comprehensive performance. High entropy alloys (HEAs), owing to their unique multi-principal element design, exhibit core potentials, such as high strength, high hardness, and excellent dynamic fracture toughness, thereby making them highly promising candidate materials for new-generation liners. In this study, the CoCrFeMnNi high entropy alloy was prepared via selective laser melting (SLM) technology, and the mechanical properties of the alloy were tested under quasi-static and dynamic loadings. The Johnson-Cook (J-C) dynamic constitutive model and related parameters for the CoCrFeMnNi HEA were determined. Using LS-DYNA, shaped charge jet formation models for both copper and high entropy alloy were established, and numerical simulations were carried out on the processes of jet formation and target penetration for copper and HEA. The research results indicate that, when compared with copper, the CoCrFeMnNi HEA liner can form a more stable and continuous jet. Its unique formation and stretching-breakup mechanisms ultimately result in greater penetration depth, confirming the significant advantage of high entropy alloys in the enhanced damage effect.

Deep space exploration faces challenges from extreme temperatures and complex high-speed operating environments, placing higher demands on the low-temperature impact resistance of materials. In this study, a low-temperature Hopkinson bar impact experimental device was developed to achieve dynamic loading of materials under ultra-low temperature conditions within a vacuum liquid helium environment. The dynamic mechanical response of 301 stainless steel produced by two rolling processes was investigated under the combined effects of low temperature (30–298 K) and high strain rates (4000–5000 s⁻¹). Experimental results show that the yield strength of both materials exhibits a significant negative correlation with temperature and a positive correlation with strain rate. The unidirectionally rolled samples displayed an anomalous increase in toughness at 77 K. The study indicates that the unidirectional rolling process induces a higher content of martensitic phase, thereby endowing the material with greater strength. Microstructural characterization results reveal that the anomalies in macroscopic mechanical behavior stem from the competition of deformation mechanisms. At room temperature, the samples mainly exhibit a toughness fracture mechanism, dominated by ductile dimples, whereas at low temperatures, they transition to a brittle fracture mode, dominated by quasi-cleavage. Based on this, the Johnson-Cook constitutive model was used to fit the mechanical properties, demonstrating good consistency with the experimental results. This research provides important experimental methods and theoretical support for the dynamic strength and toughness design of metallic materials under extreme low-temperature impact conditions.

The space debris problem has become one of the most pressing challenges in the field of space environment protection. Currently, most spacecraft shielding systems adopt Whipple-type structures, in which aluminum alloys are commonly used as bumper materials. In this study, the smoothed particle hydrodynamics (SPH) method implemented in the AUTODYN software was employed to numerically investigate the hypervelocity impact of spherical projectiles on high-entropy alloy (HEA) protective structures. The characteristics of the resulting debris clouds, including fragment number, mass distribution, and momentum, were systematically analyzed under various impact conditions. In addition, the effects of impact velocity and the ratio of bumper thickness to projectile diameter (t/D) on the hypervelocity impact response of HEA shielding structures were examined. The results show that, under identical impact conditions, the debris cloud characteristics generated by HEA protective structures differ significantly from those of aluminum alloy structures, namely: the total number of fragments increases by approximately 51.86%; the number of small-mass fragments increases by about 79.56%, while the number of large-mass fragments decreases; and the maximum debris cloud momentum along the impact direction (z-direction) is less than 75% of that associated with aluminum alloy structures across multiple projectile diameters. Parametric analyses indicate that the expansion of the debris cloud is primarily governed by impact velocity, with higher velocities leading to faster expansion, while the influence of the t/D is relatively minor. In contrast, the mass and kinetic energy of hazardous fragments (large-mass/high-energy fragments) are mainly affected by t/D, with higher values resulting in greater impact severity. These findings provide theoretical support and reference for the application of high-entropy alloys in next-generation spacecraft shielding structures.