Bj. Li et Cg. Chao, MECHANICAL-PROPERTIES AND 95-DEGREES-C AGING CHARACTERISTICS OF ZIRCON-REINFORCED ZN-4AL-3CU ALLOY, Metallurgical and materials transactions. A, Physical metallurgy andmaterials science, 27(3), 1996, pp. 809-818
A process for preparing zinc alloy castings containing dispersions of
zircon particles is described. Composites were prepared by stirring zi
rcon particles in Zn-4Al-3Cu (ZAS) alloy melts and subsequently castin
g these melts in permanent molds. It was found that additions of zirco
n resulted in an increase in the sliding wear resistance and in the pr
oportional limit in compression. The aging characteristics of the ZAS
alloy have also been investigated by hardness tests, dilatometry techn
ique, and transmission electron microscopy observations. There are two
kinds of precipitates that occur during the aging process. The alpha-
phase precipitates from the eta phase in the early stage of aging and
the copper-rich epsilon-phase precipitates from the eta phase in the l
ater stage of aging. Therefore, there are two peaks in the hardening c
urve caused by both alpha-phase and epsilon-phase precipitation. The a
lpha-phase precipitation induces the dimensional shrinkage, and the co
pper-rich epsilon phase precipitation results in dimensional expansion
. Zircon particles existing in ZAS alloy reduce the maximum shrinkage
from 353 X 10(-6) for the monolith to 167 x 10(-6) for the composite.
Two groups of parallel alpha-phase plates had formed within the eta de
ndrite during aging at 95 degrees C. The orientation relationship betw
een the alpha phase and matrix was determined as [(1) over bar 101](<e
ta)>//[l (1) over bar 0](alphaalpha), (11 (2) over bar 0)(eta)//(111)(
alpha).