First in situ observation of partial dislocation mediated plastic flow in shocked single-crystal aluminum Fig. 1 a Incident X-ray pulse and loading laser layout for time-resolved XRD. b Shaped flat-top laser profile in experiments. c The modulated spect

Recent experimental findings from the research team led by Prof. Jianbo Hu at the Institute of Fluid Physics, China Academy of Engineering Physics (CAEP), revealed partial dislocation-mediated plastic flow in shock-loaded single-crystal aluminum.​​ The experiment was conducted at the PF-AR NW14A beamline of the High Energy Accelerator Research Organization (KEK). Utilizing laser ablation to generate shock waves and employing ultra-bright, ultra-short X-ray pulses from synchrotron radiation, the team captured in situ Laue diffraction patterns of single-crystal Al during dynamic loading. ​​This work provides the first experimental evidence of partial-dislocation-dominated plastic flow in shock-compressed single-crystal Al​​, enabling analysis of the distinct deformation mechanisms between quasi-static and dynamic loading in aluminum—a high stacking fault energy metal. ​​These findings offer new insights into the plastic deformation of aluminum under high strain rates and establish novel theoretical and experimental foundations for multi-scale research on material performance under extreme conditions.​

The related findings were recently published in Science Partner Journal Ultrafast Science under the title "First in situ observation of partial dislocation mediated plastic flow in shocked single-crystal aluminum".​

Research outlines

Single-crystal aluminum (Al), characterized by its face-centered cubic (FCC) lattice structure, represents a typical high-stacking-fault-energy metal. Partial dislocation activity (stacking faults) has never been observed in quasi-static loading or shock-recovery experiments. However, molecular dynamics simulations indicate that partial dislocations play a critical role in the plasticity of single-crystal Al under extreme loading conditions. The transient nature of shock deformation necessitates time-resolved diagnostics, as conventional recovery experiments involving prolonged relaxation and complex mechanical processes fail to capture in situ material responses during elastic-plastic transitions. ​​Capturing incipient plasticity and elucidating microscopic deformation mechanisms under intense shock loading remain formidable experimental challenges.​​

Recent advances in ultra-bright, ultra-short X-ray pulse sources have demonstrated the considerable potential of time-resolved X-ray diffraction (TXRD) for capturing in situ lattice evolution, thereby enabling the characterization of dynamic material behavior under shock loading. ​​This study employed synchrotron radiation X-rays to acquire in situ Laue diffraction patterns of laser-shocked single-crystal Al.​​ Through plasticity matrix analysis constrained by uniaxial-strain boundary conditions, it has conclusively determined the dominance of partial dislocations in single-crystal Al plastic flow. Figure 2 presents TXRD results along the [100] and [110] crystallographic orientations, showcasing time-resolved Laue diffraction patterns obtained at varying delay times. ​​Under the characteristic "uniaxial-strain, triaxial-stress" constraints of shock loading, systematic analysis of Laue spot evolution via slip-system deformation tensors—cross-validated with experimental patterns—confirms that partial dislocation-mediated deformation exhibits diffraction signatures fully consistent with experimental Laue configurations in both orientations.​​ This conclusively establishes partial-dislocation-dominated plastic flow in shocked single-crystal Al.

Building upon the diffraction analysis, researchers employed molecular dynamics (MD) simulations to model dislocation motion and stacking fault configurations in single-crystal Al during shock compression. ​​By calculating the resolved shear stress across slip systems under different loading orientations, the study elucidated the distinct deformation responses along the [100] and [110] crystallographic directions.​​ The simulation results were corroborated by experimental analysis, further revealing atomic-scale evolution processes in shock-loaded single-crystal Al. ​​This synergistic integration of MD simulations with TXRD experiments establishes a robust framework for investigating in situ plastic deformation of materials under high-strain-rate conditions.​

Summary

This study employs time-resolved X-ray Laue diffraction to capture direct in situ evidence establishing the dominance of partial dislocation activity in governing plastic flow within shock-loaded single-crystal aluminum—a prototypical high-stacking-fault-energy metal.​​ This paradigm-shifting discovery overturns conventional understanding, as partial dislocation behavior had never been experimentally observed in such high-stacking-fault-energy materials during prior quasi-static loading or shock-recovery experiments. ​​The work successfully reconciles molecular dynamics predictions with experimental observations​​, resolving the longstanding challenge of capturing transient plastic deformation mechanisms under extreme conditions. ​​The revealed microscopic processes provide crucial theoretical foundations and novel perspectives for developing physics-based constitutive models of metallic materials subjected to extreme dynamic loading.​

About authors

Jianbo Hu, researcher at the Institute of Fluid Physics, China Academy of Engineering Physics, is mainly engaged in multi-scale research on the service performance of materials under extreme conditions.

Mengyang Zhou, doctoral candidate at the Institute of Fluid Physics, China Academy of Engineering Physics, is mainly engaged in in situ research on materials plastic deformation under extreme loading conditions.