Point defects and the B2 to fcc transformation in milled FeRh
- Washington State Univ., Pullman, WA (United States). Dept. of Physics
Moessbauer measurements were made on FeRh containing 52 atomic percent (at.%) Fe after mechanical milling for different times in a high-energy SPEX 8000 vibrator mill. Hyperfine fields are compared with fields for annealed ferromagnetic (F) samples having the B2 structure in the range 52--58 at.% fe. For annealed F samples, hyperfine field shifts of {minus}1.66 T and {minus}1.12 T were detected at majority Fe{sub Fe} and minority Fe{sub Rh} probes due to Fe{sub Rh} antisite atoms in, respectively, the first and second atomic shells. Analysis of dipolar fields indicates that the magnetization lies along the <110> direction. The transformation from F B2 phase to a metastable paramagnetic fcc phase was observed that was half complete in 8 minutes. Analysis of spectra for the milled F B2 phase show that a second point defect was produced by milling that induces shifts of +6 T and +8.5 T, respectively, at majority and minority probes. Many-spectra fits were made under different defect models that led to the conclusion that milling produces point defects in the triple-defect configuration: 2 Fe-vacancies and 1 Fe-antisite atom. Defect concentrations were determined and show that the fractional concentration of vacancies on the Fe-sublattice increases linearly with milling time, reaching 3 at.% after 8 minutes, a very large value. The rate of transformation from B2 to fcc phase appears to be independent of the concentrations of point defects in the B2 phase, indicating that the transformation is purely stress-induced, as in a martensite transformation.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 323526
- Report Number(s):
- CONF-971201-; TRN: IM9911%%140
- Resource Relation:
- Conference: 1997 fall meeting of the Materials Research Society, Boston, MA (United States), 1-5 Dec 1997; Other Information: PBD: 1998; Related Information: Is Part Of Phase transformations and systems driven far from equilibrium; Ma, E. [ed.] [Louisiana State Univ., Baton Rouge, LA (United States)]; Atzmon, M. [ed.] [Univ. of Michigan, Ann Arbor, MI (United States)]; Bellon, P. [ed.] [Univ. of Illinois, Urbana, IL (United States)]; Trivedi, R. [ed.] [Ames Lab., IA (United States)]|[Iowa State Univ., Ames, IA (United States)]; PB: 703 p.; Materials Research Society symposium proceedings, Volume 481
- Country of Publication:
- United States
- Language:
- English
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