Composition dependence of the elastic constants of beta-phase and (alpha+beta)-phase PdHx.
We have measured the composition and temperature dependence of the shear moduli C' and C(44) for two-phase (alpha+beta)- and single-phase beta-PdH(x). In the two-phase region, the alpha- and beta-phases are coherent. Here, the composition dependence of C(44) and C' deviate negatively from a Vegard-type volume average. We attribute the deviations to two effects: (1) the partly in-series arrangement of the precipitate and matrix phases, relative to the externally applied stress, and (2) thermally activated anelastic relaxations involving the rapid motion of H interstitial atoms, leading to slight changes in the shape of coherent precipitates. The first effect is present for both C' and C(44) and is temperature-independent, whereas the second is present only for C' and is strongly temperature-dependent.
Safarik
D J
DJ
Material Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. dsafarik@lanl.gov
Schwarz
R B
RB
Paglieri
S N
SN
Quintana
R L
RL
Tuggle
D G
DG
Byler
D D
DD