Precipitation and grain-boundary strengthening of Al-added CoCrNi medium-entropy alloys

[Display omitted] •AlXCoCrNi exhibits an abrupt hardening with 7.7 at.% of Al.•Heterogeneous precipitation of the B2 phase leads to precipitation hardening.•Hindered grain growth by precipitation leads to grain refinement.•Grain boundary wetting in the high-energy facets of twin boundary is discusse...

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Bibliographic Details
Published in:Materials letters 2019-09, Vol.250, p.127-130
Main Authors: Lee, Donghee, Jeong, Hyeon-Uk, Lee, Keun-Hyo, Jeon, Jong Bae, Park, Nokeun
Format: Article
Language:English
Subjects:
Aluminum
B2 phase
Casting alloys
CoCrNi medium-entropy alloy
Cold rolling
Grain boundaries
Grain growth
Hardness
Hardness measurement
Heterogeneous precipitation
Intermetallic phases
Materials science
Medium entropy alloys
Metals and alloys
Microstructural analysis
Sigma phase
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Summary:[Display omitted] •AlXCoCrNi exhibits an abrupt hardening with 7.7 at.% of Al.•Heterogeneous precipitation of the B2 phase leads to precipitation hardening.•Hindered grain growth by precipitation leads to grain refinement.•Grain boundary wetting in the high-energy facets of twin boundary is discussed. Herein, we report the hardening effect of Al in CoCrNi medium-entropy alloys. Al contents of up to 25 at% were added to CoCrNi and hardness measurements and phase investigation of the as-cast alloys were subsequently performed. The hardness of the as-cast alloys increased with increasing Al content and the BCC/B2 and sigma phase fraction increased as well. An additional hardness measurement was performed on cold-rolled and annealed alloys, and revealed a sharp increase in the hardness of Al7.7CoCrNi. Microstructural analysis of Al7.7CoCrNi was also performed and significant heterogeneous precipitation of the B2 phase was observed. Our findings demonstrated that heterogeneous precipitation owing to Al addition resulted in the abrupt hardening of Al7.7CoCrNi. However, the retarded grain growth due to heterogeneous precipitation may have more significantly contributed to the hardening effect.
ISSN:0167-577X
1873-4979
DOI:10.1016/j.matlet.2019.04.129