Role of chromium oxides and carbides in strengthening CoCrFeNi multi-principle element alloys

Abstract

Multi-principal element alloys (MPEAs) can potentially offer exceptional material properties, but their complex, costly manufacturing limits their scalability. Chemical complexity and complex manufacturing processes lead to the formation of some secondary phases, which have a significant impact on the final properties. In this work, chromium compound dispersoid enhancements (Cr- oxides and carbides) were formed in CoCrFeNi MPEAs to enhance their microstructural and high-temperature mechanical properties. A single FCC phase was observed in the arc melted (AM) samples, chromium oxides were detected in the gas-atomized (GA) samples, and Cr2O3 with Cr23C6 or Cr7C3 was found in the mechanically alloyed (MA)samples depending on the sintering temperature. Mechanical tests at room temperature and 575{\deg}C, where no phase evolution is expected, showed that the GA samples with oxides achieved enhanced mechanical properties at 575{\deg}C. This was co-induced by precipitation strengthening, recrystallization suppression, and twinning-induced plasticity. The MA samples with carbides exhibited high strength but low ductility, with Cr7C3 outperforming Cr23C6 because of its lower hardness and twinning effects. This work links chromium compound evolution to mechanical performance of MPEAs, offering insights to optimize HEA production for high-temperature applications through controlled phase formation.