Mechanism of solid-state reaction for fabrication of new glassy V 45 Zr 22 Ni 22 Cu 11 alloy powders and subsequent cons
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A. Inoue Institute for Materials Research, Tohoku University, Katahira 2-1-1 Sendai, Miyagi 980-8577, Japan (Received 11 April 2003; accepted 15 July 2003)
A single glassy phase of V45Zr22Ni22Cu11 alloy powders was synthesized by milling the elemental alloying powders in an argon atmosphere using a low-energy ball-milling technique. During the early and intermediate stages of milling, the atoms of Zr, Ni, and Cu migrated and diffused into the V (base material) lattice to form a body-centered-cubic (bcc) solid-solution, which transformed into a glassy phase with the same composition upon annealing at 850 K for 300 s in an argon atmosphere differential scanning calorimeter (thermally-enhanced glass formation reaction). As the milling time increased, the powders were subjected to continuous defects and lattice imperfections that led to a gradual change in the free energy so that solid-solution phase was transformed (mechanically enhanced glass formation reaction) to another metastable phase (glassy). Toward the end of the milling processing time, the bcc solid-solution transformed completely into a single glassy phase with the same composition. The glass-transition temperature, the crystallization temperature, and the enthalpy change of crystallization of the fabricated glassy powders were 741 K, 884 K, and −2.18 kJ/mol, respectively. This fabricated glassy alloy showed a wide supercooled liquid region (143 K) of metallic glassy alloy. The glassy powders were compacted in an argon gas atmosphere at 864 K with a pressure of 780 MPa using a hot-pressing technique. The consolidated sample was fully dense (above 99.2%) and maintained its chemically homogeneous glassy structure. The Vickers microhardness of the consolidated glassy V45Zr22Ni22Cu11 alloy was measured and found to be in the range between 6.89 GPa to 7.02 GPa.
I. INTRODUCTION 1,2
In the last 30 years, mechanical alloying (MA) using the ball-milling and/or rod-milling3 techniques has made remarkable progress for preparing several advanced engineering materials at room temperature.4 Among these useful materials, metallic glassy alloys, with their unique short-range atomic order and desirable properties that
a)
Address all correspondence to this author. Present address: Mining, Metallurgical and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Nasr City 11371, Cairo, Egypt. e-mail: [email protected] b) Present address: R&D Institute of Metals and Composites for Future Industries, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 9808577, Japan. J. Mater. Res., Vol. 18, No. 10, Oct 2003
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make them pioneer materials for several industrial applications,5–8 have been synthesized by the MA method.9–14 The worldwide interest in the metallic glassy materials, which represent the ultimate state of solid metastability, has been sustained to a great degree by the clear benefits seen in the use of them in a number of application areas.15 Inert gas atomization technique has been considere
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