Mechanically induced devitrifications of ball-milled Zr 70 Pd 20 Ni 10 glassy alloy powders
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J. Saida Inoue SuperLiquid Glass Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Yagiyama-Minami 2-1-1, Sendai 982-0607, Japan, and Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan
A. Inoue Institute for Materials Research, Tohoku University, Sendai, Japan (Received 30 June 2002; accepted 30 October 2002)
Mechanical alloying using a high-energy ball milling technique was used to fabricate a single glassy phase of Zr70Pd20Ni10 alloy powders after 100 h milling time. Annealing the glassy powders at a temperature just below the crystallization onset temperature led to thermally enhanced devitrification and the formation of a metastable big-cube phase with a lattice constant of 1.2289 nm. The same metastable phase was obtained upon subjecting the end product of the glassy powders to further ball milling time (150 h). This metastable big-cube phase could no longer withstand the shear and impact stresses generated by the milling media and transformed into a new metastable phase of face-centered cubic Zr70Pd20Ni10. The lattice constant of this metastable phase was calculated to be 0.56838 nm. These metastable phases are new and have never been, so far as we know, reported for the ternary Zr–Pd–Ni system or its binary phase relations. Glassy alloys, with their unique absence of long-range atomic order, exhibit unusual properties that make them pioneer materials for several applications.1–3 Metallic glasses can be fabricated by a wide variety of techniques.4 Of these, the mechanical alloying (MA) method, where the reaction between the diffusion couples takes place at low temperatures (far below the crystallization of the glassy phase), has been considered as a powerful technique for fabrication of wide varieties of glassy materials that cannot be easily obtained by the conventional melting and casting techniques.5 The amorphization and crystallization of Zr-based glassy alloys exhibit many interesting characteristics and also pose some difficult questions (see for example Refs. 6–8). The present study was undertaken to investigate the structural changes that take place during ball milling of elemental Zr70Pd20Ni10 powders. The stability of the obtained glassy alloys against the impact and shear forces generated by the milling media is demonstrated in this communication. Pure elemental powders (99.9%) of Zr (50 m), Pd (10 m), and Ni (10 m) were balanced to give the nominal composition of Zr70Pd20Ni10 (at.%) and mixed
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Present address: Mining, Metallurgical and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Nasr City 11371, Cairo, Egypt. e-mail: [email protected]
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http://journals.cambridge.org
J. Mater. Res., Vol. 18, No. 2, Feb 2003 Downloaded: 13 Mar 2015
in a glove box under a purified argon atmosphere. The mixed powders were then sealed into a tempered chromium steel vial (250 ml in volume) together with 50 tempered chrome steel balls (10 mm in diameter), using a ball-to-powder weig
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