Orientation-dependent phase transformation pathways and energy partition in shock-compressed FeCoCrCu high-entropy alloy

Abstract

High-entropy alloys exhibit excellent mechanical properties under extreme dynamic loading, yet their orientation-dependent shock deformation and energy-partition mechanisms remain unclear. Here, large-scale molecular-dynamics simulations are performed to investigate single-crystalline FeCoCrCu high-entropy alloy shocked along the [100], [110], [111], and [012] orientations at particle velocities up to 1.2 km/s. The results reveal pronounced anisotropy in Hugoniot states, wave structures, stress relaxation, and microstructural evolution. Shockley-partial-mediated FCC → HCP transformation is the primary deformation pathway in all orientations, while an additional FCC → BCC transformation is activated mainly in the [100] and [012] orientations under high-intensity loading. In situ lattice analysis and simulated XRD profiles support a Bain-type FCC → body-centered tetragonal-like → BCC pathway. The [100] orientation forms metastable, patch-like BCC-like intermediates, whereas the low-symmetry [012] orientation promotes a more continuous BCC transformed region through compression–shear coupling, leading to efficient shear-stress relaxation. Phase-resolved potential-energy statistics show that BCC atoms possess higher mean potential energy than FCC/HCP atoms, suggesting transient structural-energy storage and delayed local thermalization. These findings clarify how crystallographic orientation governs the competition between dislocation-mediated plasticity and phase-transformation-assisted deformation in shock-compressed FeCoCrCu high-entropy alloy.