J. Saida et al., Investigation of the stability of glassy state in the Zr- and Hf-based glassy alloys correlated with their transformation behavior, J MATER RES, 16(12), 2001, pp. 3389-3401
The transformation behavior from glassy state was investigated in Zr- and H
f-based glassy alloys. The primary phases are metastable face-centered-cubi
c (fcc) Zr2Ni and fee Hf2Ni phases in the Zr65Al7.5Ni10Cu17.5 and Hf65Al7.5
Ni10Cu17.5 glassy alloys, respectively. By substitution of 5 at.% Pd for Cu
, the primary phase changes to an icosahedral quasicrystalline phase in bot
h alloys. It is found that the addition of elements, which have a positive
or weak chemical affinity with one of the constitutional elements in the Zr
-Al-Ni-Cu and Hf-Al-Ni-Cu glassy alloys, is effective for the precipitation
of the icosahedral phase. It is suggested that Pd plays a dominant role in
an increase in the number of nucleation sites. Since an icosahedron is con
tained as a structure unit in the icosahedral, fee Zr2Ni and fee Hf2Ni phas
es, it is implied that these phases are correlated with the local icosahedr
al order. The high-resolution transmission electron microscopy images of th
e as-spun Zr65Al7.5Ni10Cu7.5Pd10 and Hf65Al7.5Ni10Cu12.5Pd5 alloys reveal a
possibility of the existence of the icosahedral ordered regions. It is the
refore, concluded that the icosahedral short- or medium-range order exists
and it stabilizes the glassy state in the Zr- and Hf-based multicomponent a
lloys.