Unraveling Anisotropy in Crystalline Orientation under Shock-Induced Dynamic Responses in High-Entropy Alloy Co₂₅Ni₂₅Fe₂₅Al_7.5Cu_17.5

YC Wu and JL Shao, NANOMATERIALS, 13, 2446 (2023).

DOI: 10.3390/nano13172446

Shock-induced plastic deformation and spall damage in the single- crystalline FCC Co25Ni25Fe25Al7.5Cu17.5 high-entropy alloy (HEA) under varying shock intensities were system-atically investigated using large- scale molecular dynamics simulations. The study reveals the significant influence of crystalline orientation on the deformation mechanism and spall damage. Specifically, the shock wave velocities in the 110 and 111 directions are significantly higher than that in the 001 direction, resulting in a two-zone elastic-plastic shock wave structure observed in the 110 and 111 samples, while only a single-wave structure is found in the 001 sample. The plastic deformation is dominated by the FCC to BCC transformation following the Bain path and a small amount of stacking faults during the compression stage in the 001 sample, whereas it de-pends on the stacking faults induced by Shockley dislocation motion in the 110 and 111 samples. The stacking faults and phase transformation in the 001 sample exhibit high reversibility under release effects, while extensive dislocations are present in the 110 and 111 samples after release. Interestingly, tension-strain-induced FCC to BCC phase transformation is observed in the 001 sample during the release stage, resulting in increased spall strength compared to the 110 and 111 samples. The spall strength estimated from both bulk and free surface velocity history shows reasonable consistency. Additionally, the spall strength remains stable with increasing shock inten-sities. The study discusses in detail the shock wave propagation, microstructure change, and spall damage evolution. Overall, our comprehensive studies provide deep insights into the deformation and fracture mechanisms of Co25Ni25Fe25Al7.5Cu17.5 HEA under shock loading, contributing to a better understanding of dynamic deformation under extreme environments.

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