Changes in microstructure and phonon thermal conductivity in a lamellar dual-phase high-entropy alloy under tensile strain

This study investigates the evolution of phonon thermal conductivity and microstructural response in a dual-phase, bicontinuous lamellar high-entropy alloy (HEA) subjected to tensile deformation. Using non-equilibrium molecular dynamics simulations with a multicomponent embedded-atom method potential, we examine a heterostructure composed of a chemically disordered face-centered cubic (FCC) FeNiCrCo phase and a B2 phase Al(FeNiCrCo) phase. The lamellae are oriented in the z direction, giving this HEA an anisotropic structure. We find that both the longitudinal ( κ z ) and transverse ( κ x ) components of the thermal conductivity initially decrease with increasing strain, but reach a plateau for strains exceeding approximately 10%. This stabilization is primarily associated with the FCC phase, which maintains an effective phonon transport pathway despite substantial strain-induced redistribution of vibrational modes in the B2 phase. The mechanical response is governed by dislocation-mediated plasticity, the formation of amorphization bands in the B2 phase, and stacking fault activity in the FCC phase. Our analysis indicates that the reduction in thermal conductivity is dominated by phonon scattering from the elastic stress fields of dislocations and stacking faults. Finally, the simulated thermal conductivities are shown to be in good agreement with an effective-medium composite model, providing a predictive framework for thermal transport in mechanically deformed complex alloys. To our knowledge, this study provides the first direct link between strain-induced lamellar amorphization, stacking-fault accumulation, and anisotropic phonon thermal conductivity in a dual-phase HEA.