Adaptive attenuation of hierarchical composition fluctuations augments the plastic strain of a high entropy steel

Abstract

A body-centred cubic (BCC) high entropy steel with a spinodal-like nanopattern and atomic-scale local chemical fluctuations exhibits controlled attenuation of its chemical complexity with deformation. Changes in the chemical composition of the spinodal structure measured using energy dispersive X-ray spectroscopy reveal that the average composition peak-to-peak amplitude decreases by 67% from 4.9 at.% to 1.6 at.% with increasing strain. On the other hand, the short-range chemical fluctuations, assessed with atomic strain mapping, displays a 48% decrease in the average strain peak-to-peak amplitude from 3.03 at.% to 1.59 at.% under mechanical loading. The reduction in local strain brought about by increased chemical homogeneity at both levels enables more uniform, steady deformation leading to extended ductility (13.7 ± 1.9%), all the while maintaining ultrahigh strength (2.92 ± 0.36 GPa, placing it among the highest values reported). The interactions between dislocations and concentration waves are identified and found to be responsible for this compelling effect on the newly created steel.