Microstructure and properties of a CoCrFeNiMn high-entropy alloy processed by equal-channel angular pressing

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:705

Article

Shahmir, Hamed¹  Mousavi, Tayebeh²  He, Junyang³  Lu, Zhaoping³  Kawasaki, Megumi^4,5  Langdon, Terence G.¹ 

[1] Univ Southampton, Fac Engn & Environm, Mat Res Grp, Southampton SO17 1BJ, Hants, England

[2] Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England

[3] Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing 10083, Peoples R China

[4] Hanyang Univ, Div Mat Sci & Engn, Seoul 133791, South Korea

[5] Hanyang Univ, Res Inst Ind Sci, Seoul 133791, South Korea

关键词: CoCrFeNiMn;    High-entropy alloy;    Equal-channel angular pressing;    Post-deformation annealing;    Severe plastic deformation;   

DOI  :  10.1016/j.msea.2017.08.083

来源: Elsevier

【 摘 要 】

A CoCrFeNiMn high-entropy alloy (HEA) was processed by equal-channel angular pressing (ECAP) for up to four passes at 673 K and the results show that the strength increases gradually with increasing straining up to similar to 1 GPa with an elongation to failure of similar to 35% after four passes of ECAP. In this condition, the microstructure is a single-phase ultrafine-grained (UFG) CoCrFeNiMn HEA with an average grain size of 100 nm and a high dislocation density. This UFG HEA was subjected to post-deformation annealing (PDA) at temperatures of 673-1073 K for 60 min and it is shown that the hardness increases slightly due to precipitation to 773 K and then decreases to 1073 K due to a combination of recrystallization, grain growth and a dissolution of precipitates. The formation of brittle sigma-phase precipitates improves the strength significantly but with a minor decrease in ductility. Annealing at the peak temperature of 773 K produces a very high yield strength of similar to 1015 MPa and an ultimate strength of similar to 1080 MPa together with an excellent elongation to failure of similar to 30%. An analysis of the data shows that grain boundary strengthening is the most important strengthening mechanism in these ECAP samples both before and after PDA.

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