Suzuki hardening and segregation in Co0.95Cr0.8Fe0.25Ni1.8Mo0.475 high-entropy alloys

A Co0.95Cr0.8Fe0.25Ni1.8Mo0.475 high-entropy alloy was heavily cold-rolled and subsequently aged at 773 K. Aging-induced Suzuki hardening was observed. High-angle annular dark-field scanning transmission electron microscopy imaging and the corresponding energy dispersive X-ray spectroscopy elemental distribution mapping suggested the enrichment of Co atoms at stacking faults (SFs), which pinned down partial dislocations and enhanced the resistance of the alloy to plastic deformation. Furthermore, the enrichment of Co and Mo atoms at SFs was observed in a low dislocated, strain-aged specimen. The significant difference in the SF density of the specimens led to difference in segregation. The local stacking fault energy (SFE) with the segregation of Co and Mo atoms was calculated as -30.6 mJ/m2 at the aging temperature. The negative SFE did not restrict the SF expansion, indirectly resulting in the formation of wide SFs.

Automated summary

A Co0.95Cr0.8Fe0.25Ni1.8Mo0.475 high-entropy alloy underwent heavy cold rolling and subsequent aging at 773 K, resulting in Suzuki hardening. Enrichment of Co atoms at stacking faults (SFs) was observed, which pinned down partial dislocations and enhanced the deformation resistance. Additionally, enrichment of Co and Mo atoms at SFs was observed in a low dislocated, strain-aged specimen, leading to differences in segregation. The calculated local stacking fault energy (SFE) with the segregation of Co and Mo atoms was -30.6 mJ/m2 at the aging temperature, indirectly leading to the formation of wide SFs.