Effect of multiple oxides on the mechanical properties of CoCrFeMnNi high-entropy alloy matrix composites

ABSTRACT

This study investigates the oxide formation behaviour and mechanical properties of oxide-dispersion-strengthened (ODS) CoCrFeMnNi high-entropy alloy (HEA) matrix composites produced via powder metallurgy. Grain boundary strengthening, solid solution hardening, and precipitation hardening were controlled by varying the duration of mechanical milling and heat treatment durations. The grain size decreased significantly upon milling and it increased to the range of hundreds of nanometres with the heat treatment. Although ex situ-added Y₂O₃ nanoparticles were uniformly dispersed in the HEA matrix regardless of the milling duration and heat treatment time, different types of in situ oxides, such as Cr- and Mn-oxides, were formed during the heat treatment. Longer milling times led to more crystal defects (e.g. grain boundaries and dislocations) and stored energy in the HEA matrix, thereby stimulating second phase precipitation and oxide formation. Under optimal conditions, the ODS-HEA composites exhibited a good balance between yield strength and elongation in compression.

KEYWORDS:

• High-entropy alloys
• powder metallurgy
• oxide-dispersion strengthening
• Y₂O₃ nanoparticles
• alloy powder
• nano-composite

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) (No. 2020R1A2C2101047 and No.2020M3H4A3106736P).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Research Foundation of Korea [grant number 2020M3H4A3106736P], [grant number 2020R1A2C2101047].