EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The best-known and widely-studied among high-entropy alloys is the so-called Cantor alloy (CoCrFeMnNi) with a face-centered cubic (fcc) structure. Cantor alloy and its derivatives have high ductility at room and cryogenic temperatures, , excellent fracture and impact toughness, etc., but mostly have quite low strength. It is known that doping with interstitial elements can lead to a significant hardening of alloys. In present work, we studied the effect of nitrogen doping on the structure and mechanical properties evolution of the equiatomic CoCrFeMnNi alloy during thermomechanical processing.
CoCrFeNiMn high-entropy alloys with different content of nitrogen (0.5-2.0 at.%) were prepared by induction melting. The as-cast alloys were cold rolled to a thickness reduction of 80%, followed by annealing in the temperature range from 700 to 1000°C for 1 hour.
The alloys with 0.5-1.0 at.% of N in the as-cast condition had a single fcc phase coarse-grained microstructure. An increase in the content of N to 2.0 at.% resulted in the precipitation of a small amount (~1%) of M2N nitride particles. The yield strength of the alloys increased proportionally with nitrogen content at room and cryogenic temperature. It was revealed that cold rolling with subsequent annealing results in significant grain refinement. The alloy with a low amount of N (0.5 at.%) had a single fcc phase structure. An increase in the content of N to 2.0 at.% produced fine-grained structure due to the precipitation of M2N particles. The fine-grained alloys also demonstrated attractive balance between strength and ductility both at room and cryogenic temperatures. Relationships between chemical composition, processing conditions, structure, and mechanical properties were discussed.

This study was supported by Russian Science Foundation, grant № 21-19-28005.