Linking lattice distortion to remarkable strain-hardening behavior in high-entropy alloys through a nano-to-macro multiscale model

High-entropy alloys (HEAs) exhibit remarkable strain hardening behavior in contrast to traditional alloys, yet the quantitative understanding of their mechanical origin remains elusive in the literature. In this study, the lattice-distortion-induced strain hardening in FeCoNiCr HEA is investigated by integrating experimental characterization with an atomically informed finite element framework. High-resolution transmission electron microscopy is utilized to characterize the severe lattice distortions, which are then mathematically incorporated into the model using a three-dimensional fractal function. Scaling analysis reveals that the resulting lattice-distortion-dependent stress field converges at the micrometer scale. A modified Kocks-Mecking model accounting for lattice-distortion-induced dislocation multiplication, annihilation, and cross-slip is proposed. To establish a quantitative linkage between microstructural evolution and macroscopic mechanical behavior, both the micrometer-scale lattice-distortion stress field and the modified Kocks-Mecking model are coupled into the finite element framework. The predicted stress-strain responses accurately reproduce the experimental yield strength and strain hardening behavior. By quantitatively decoupling the contributions of individual deformation mechanisms, the multiscale simulation results demonstrate that severe lattice distortion and deformation twinning are the primary origins of the enhanced strain-hardening capacity in the alloy. This work provides a robust quantitative microstructure-property linkage, deepening the understanding of fundamental deformation mechanisms in complex concentrated alloys.