Abstract
There have been numerous efforts to develop creep-resistant materials strengthened by incoherent particles at high temperatures and stresses in response to future energy needs for steam turbines in thermal-power plants. However, the microstructural instability of the incoherent-particle-strengthened ferritic steels limits their application to temperatures below 900 K. Here, we report a novel ferritic alloy with the excellent creep resistance enhanced by coherent hierarchical precipitates, using the integrated experimental (transmission-electron microscopy/scanning-transmission-electron microscopy, in-situ neutron diffraction, and atom-probe tomography) and theoretical (crystal-plasticity finite-element modeling) approaches. This alloy is strengthened by nano-scaled L2 1 -Ni 2 TiAl (Heusler phase)-based precipitates, which themselves contain coherent nano-scaled B2 zones. These coherent hierarchical precipitates are uniformly distributed within the Fe matrix. Our hierarchical structure material exhibits the superior creep resistance at 973 K in terms of the minimal creep rate, which is four orders of magnitude lower than that of conventional ferritic steels. These results provide a new alloy-design strategy using the novel concept of hierarchical precipitates and the fundamental science for developing creep-resistant ferritic alloys. The present research will broaden the applications of ferritic alloys to higher temperatures.
Original language | English |
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Article number | 16327 |
Journal | Scientific Reports |
Volume | 5 |
DOIs | |
State | Published - Nov 9 2015 |
Funding
The research is supported by the Department of Energy (DOE), Office of Fossil Energy Program, under Grants of DE-09NT0008089, DE-FE0005868, DE-FE-0011194, and DE-FE-0024054 with Mr. Richard Dunst, Mr. Vito Cedro, Dr. Patricia Rawls, Mr. Steven Markovich, and Dr. Jessica Mullen as the program managers. The work has been benefitted from the use of the Lujan Neutron Scattering Center at the Los Alamos Neutron Science Center (LANSCE), which is funded by the Office of Basic Energy Sciences (DOE). Los Alamos National Laboratory is operated by the Los Alamos National Security LLC under the DOE Contract number of DE-AC52-06NA-25396. This research was supported by the Center for Nanophase Materials Sciences (CNMS) at the Oak Ridge National Laboratory (ORNL), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. YFG was supported by the US Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.