Abstract
Secondary phases, either introduced by alloying or heat treatment, are commonly present in most high-entropy alloys (HEAs). Understanding the formation of secondary phases at high temperatures, and their effect on mechanical properties, is a critical issue that is undertaken in the present study, using the AlxCoCrFeNi (x = 0.3, 0.5, and 0.7) as a model alloy. The in-situ transmission-electron-microscopy (TEM) heating observation, an atom-probe-tomography (APT) study for the reference starting materials (Al0.3 and Al0.5 alloys), and thermodynamic calculations for all three alloys, are performed to investigate (1) the aluminum effect on the secondary-phase fractions, (2) the annealing-twinning formation in the face-centered-cubic (FCC) matrix, (3) the strengthening effect of the secondary ordered body-centered-cubic (B2) phase, and (4) the nucleation path of the σ secondary phase thoroughly. The present work will substantially optimize the alloy design of HEAs and facilitate applications of HEAs to a wide temperature range.
| Original language | English |
|---|---|
| Pages (from-to) | 206-220 |
| Number of pages | 15 |
| Journal | Acta Materialia |
| Volume | 131 |
| DOIs | |
| State | Published - Jun 1 2017 |
Funding
The present work was supported by the Royal Netherlands Academy of Science (KNAW, Amsterdam) with grant No. 11CDP003. J. C. Rao is grateful for the financial support of the National Natural Science Foundation of China (Grant No. 51572054, 51021002, and 51321061) with Y. Zhou as the group leader. H. Y. Diao, C. Kuo, and P. K. Liaw would like to acknowledge the Department of Energy (DOE), Office of Fossil Energy, National Energy Technology Laboratory (DE-FE-0008855 and DE-FE-0024054) with Mr. V. Cedro and Mr. R. Dunst as program managers. Z. Tang and P. K. Liaw thank the support from the project of DE-FE-0011194 with the DOE program manager, Dr. J. Mullen. P. K. Liaw very much appreciates the support of the U.S. Army Research Office project (W911NF-13-1-0438) with the program manager, Dr. D. M. Stepp. P. K. Liaw thanks the support from the National Science Foundation (DMR-1611180) with the program director, Dr. D. Farkas. APT was conducted at the ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility. The neutron research conducted at the ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| Office of Basic Energy Sciences | |
| Royal Netherlands Academy of Science | |
| Scientific User Facilities Division | |
| U.S. Army Research Office | W911NF-13-1-0438 |
| US Department of Energy | |
| National Science Foundation | DMR-1611180 |
| U.S. Department of Energy | |
| Office of Fossil Energy | |
| Oak Ridge National Laboratory | |
| National Energy Technology Laboratory | DE-FE-0024054, DE-FE-0008855 |
| Koninklijke Nederlandse Akademie van Wetenschappen | 11CDP003 |
| National Natural Science Foundation of China | 51021002, 51572054, 51321061 |
Keywords
- Atom-probe-tomography
- High-entropy alloy
- In-situ heating TEM
- Secondary phases
- Thermodynamic calculations