Maximum strength and dislocation patterning in multi-principal element alloys

Multi-principal element alloys (MPEAs) containing three or more components in high concentrations render a tunable chemical short-range order (SRO). Leveraging large- scale atomistic simulations, we probe the limit of Hall-Petch strengthening and deformation mechanisms in a model CrCoNi alloy and unravel chemical ordering effects. The presence of SRO appreciably increases the maximum strength and lowers the propensity for faulting and structure transformation, accompanied by intensification of planar slip and strain localization. Deformation grains exhibit notably different microstructures and dislocation patterns that prominently depend on their crystallographic orientation and the number of active slip planes. Grain of single-planar slip attains the highest volume fraction of deformation-induced structure transformation, and grain with double-slip planes develops the densest dislocation network. These results advancing the fundamental understanding of deformation mechanisms and dislocation patterning in MPEAs suggest a mechanistic strategy for tuning mechanical behavior through simultaneously tailoring grain texture and local chemical order.

Automated summary

This study investigates the influence of chemical ordering on the strengthening and deformation mechanisms in multi-principal element alloys (MPEAs). The presence of chemical short-range order (SRO) is found to significantly enhance the strength of the alloy and reduce the likelihood of faulting and structure transformation. Additionally, the microstructure and dislocation patterns in the alloy grains depend on their crystallographic orientation and the number of active slip planes. These findings contribute to a better understanding of the deformation mechanisms and dislocation patterning in MPEAs, and suggest a strategy for tuning mechanical behavior through grain texture and local chemical order.