Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5455405 | Materials Science and Engineering: A | 2017 | 36 Pages |
Abstract
A CoCrFeNiMn high-entropy alloy (HEA) was processed by equal-channel angular pressing (ECAP) for up to four passes at 673Â K and the results show that the strength increases gradually with increasing straining up to ~ 1Â GPa with an elongation to failure of ~ 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 ~ 100Â nm and a high dislocation density. This UFG HEA was subjected to post-deformation annealing (PDA) at temperatures of 673-1073Â K for 60Â min and it is shown that the hardness increases slightly due to precipitation to 773Â K and then decreases to 1073Â K due to a combination of recrystallization, grain growth and a dissolution of precipitates. The formation of brittle Ï-phase precipitates improves the strength significantly but with a minor decrease in ductility. Annealing at the peak temperature of 773Â K produces a very high yield strength of ~ 1015Â MPa and an ultimate strength of ~ 1080Â MPa together with an excellent elongation to failure of ~ 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.
Keywords
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
Hamed Shahmir, Tayebeh Mousavi, Junyang He, Zhaoping Lu, Megumi Kawasaki, Terence G. Langdon,