Abstract
The elastic properties of a γ1-FePd single crystal have been measured using the pulse-echo overlap method. The anisotropic elastic constants of this tetragonal L10 structure are explained in part by the different bond strength between Fe-Pd neighbors compared with Fe-Fe and Pd-Pd neighbors. The tetragonal elastic anisotropy as measured for the single crystal appears to depend on the remaining fraction of misoriented order variants. The anisotropy parameters for γ1-FePd are (c 44/c66) = 0.93 ± 0.04, A1 = 2c 66/(c11 - c12) = 2.78 ± 0.14 and A 2 = 4c44/(c11 + c33 - 2c 13) = 2.53 ± 0.40, implying a shear stiffness along [1 0 0] that is smaller in (0 0 1) than in (0 1 0). The magnitude of the elastic anisotropy (e.g., A1 and A2) of γ1-FePd is similar to that of some face-centered cubic metals (e.g., Au with A = 2c 44/(c11 - c12) = 2.90 and Ni with A = 2.51) and considerably larger than that of γ-TiAl (e.g., A1 = 1.44 and A2 = 1.98). However, the deviations of the considerably anisotropic elastic properties of the tetragonal γ1-FePd from that expected for an equivalent elastically anisotropic crystal of cubic symmetry are less pronounced than for γ-TiAl. In contrast to γ-TiAl, the elastic constants indicate that shearing in the (1 1 1) plane is easiest along [-1 1 0] and increases in difficulty as the shear direction changes via [-1 0 1] towards [-1 -1 2] for γ1-FePd.
Original language | British English |
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Pages (from-to) | 881-889 |
Number of pages | 9 |
Journal | Acta Materialia |
Volume | 54 |
Issue number | 4 |
DOIs | |
State | Published - Feb 2006 |
Keywords
- Elastic constants
- Single crystals
- Tetragonal FePd
- TiAl