title: Ferritic Alloys with Extreme Creep Resistance via Coherent Hierarchical Precipitates.
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 L21-Ni2TiAl (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.
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Gian
authors.initials: G
authors.lastname: Song
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Zhiqian
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Xiandong
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108.
authors.forename: Michael
authors.initials: M
authors.lastname: Rawlings
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720.
authors.forename: Christian H
authors.initials: CH
authors.lastname: Liebscher
authors.affiliation: Lujan Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Clausen
authors.affiliation: Center for Nano phase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Poplawsky
authors.affiliation: Center for Nano phase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Donovan N
authors.initials: DN
authors.lastname: Leonard
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Shenyan
authors.initials: S
authors.lastname: Huang
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Zhenke
authors.initials: Z
authors.lastname: Teng
authors.affiliation: Center for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong.
authors.forename: Chain T
authors.initials: CT
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Asta
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Yanfei
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108.
authors.forename: David C
authors.initials: DC
authors.lastname: Dunand
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108.
authors.forename: Gautam
authors.initials: G
authors.lastname: Ghosh
authors.affiliation: WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Mingwei
authors.initials: M
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108.
authors.forename: Morris E
authors.initials: ME
authors.lastname: Fine
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996-2200.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Liaw