Dislocation nucleation and shear sliding at dual-phase high-entropy alloy semi-coherent interface with atomic complexity

Abstract

Interface plays a prominent role in determining the deformation behavior of dual-phase lamellar microstructures, particularly in lamellar high-entropy alloys (HEAs) due to the inherent complexity of interfacial atomic structures. Here, we employed a combination of molecular dynamics, molecular statics, and Monte-Carlo simulations to examine the effects of interfacial lattice distortion (ILD) and interfacial chemical short-range ordering (ICSRO) on the dislocation nucleation and shear response at semi-coherent fcc/bcc interface in laminated AlCoCuFeNi HEAs. Our findings reveal that ILD introduces irregularities in the interfacial misfit, predominantly accommodating the misfit between two phases and reducing average interfacial disregistry. Besides, ICSRO differs from chemical short-range ordering in single-phase HEAs, with Fe/Cu elements showing clear preferences for bcc or fcc structural configurations, leading to significant element segregation and further reduction in interfacial disregistry. The synergistic effect of ILD and ICSRO disrupts the regularity of original misfit dislocation networks typically observed in bimetallic systems, making local areas with large disregistry as preferred dislocation nucleation sites, instead of the expected periodic misfit dislocations at the interface in conventional scenarios. Moreover, ILD and ICSRO significantly enhance shear resistance through pinning effect of random solute atoms and ICSRO clusters on the sliding pathway. Our results offer profound insight into the structure-property relationships of dual-phase HEA interfaces characterized by atomic complexity, enabling the development of HEAs with enhanced mechanical performance through the customization of their interfacial characteristics.