Preparation and thermal stability of Zr-Ti-Al-Ni-Cu amorphous powders by mechanical alloying technique |
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Authors: | C K Lin S W Liu P Y Lee |
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Affiliation: | (1) the Department of Materials Science, Feng-Chia University, Taichung, Taiwan, R.O.C.;(2) the Institute of Materials Engineering, National Taiwan Ocean University, Keelung, Taiwan, R.O.C. |
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Abstract: | This study examined the amorphization feasibility of Zr70−x−y
Ti
x
Al
y
Ni10Cu20 alloy powders by the mechanical alloying (MA) technique. According to the results, after 5 to 7 hours of milling, the mechanically
alloyed powders were amorphous basically in the ranges of 0 to 12.5 at. pct Ti and 2.5 to 17.5 at. pct Al. These ranges are
larger than those of bulk amorphous alloys prepared by a squeeze mold casting technique. Most of the amorphous mechanically
alloyed powders exhibited a wide supercooled liquid region of more than 60 K before crystallization. The glass-transition
and crystallization temperatures of mechanically alloyed samples were different from those prepared by squeeze casting. It
is suspected that different thermal properties arise from the introduction of impurities during the MA process. The amorphization
behavior of Zr50Ti7.5Al12.5Ni10Cu20 was examined in detail. The X-ray diffraction and extended X-ray absorption fine structure (EXAFS) results show the fully
amorphous powders formed after 5 hours of milling. A kinetically modified thermodynamic phase transformation process was observed
for the glass-transition behavior in the Zr50Ti7.5Al12.5Ni10Cu20 amorphous powder. |
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Keywords: | |
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