Crystallization phases of the Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 alloy after slow solidification
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. Wanderka,b) P. Schubert-Bischoff, and M-P. Macht Hahn-Meitner-Institut Berlin GmbH, Glienicker Strasse 100, 14109 Berlin, Germany
S. Friedrich Universita¨t Potsdam, Institut fu¨r Berufspa¨dagogik, Karl-Liebknecht-str. 24-25, D-14476, Golm, Germany (Received 29 November 1999; accepted 12 May 2000)
A systematic study was carried out on the equilibrium phases after slow solidification of the Zr41Ti14Cu12.5Ni10Be22.5 alloy. The crystalline microstructure of the slowly cooled melt of the alloy shows “polygons” and “plates” embedded in a fine-grained two-component matrix. To analyze the crystal structure of the different components, microdiffraction technique combining convergent beam electron diffraction and conventional selected-area electron diffraction were used. The stoichiometry of these phases was confirmed by field ion microscopy with atom probe and energy-dispersive x-ray analysis in a transmission electron microscope. The polygons were determined to be cubic (a ⳱ 1.185 nm) with space group Fm3m (cF116). The plates were found to be tetragonal (a ⳱ 0.37 nm, c ⳱ 1.137 nm) with space group I4/mmm (tI6). Its composition is (Cu + Ni)(Zr + Ti)2. One phase of the fine-grained two-component matrix was rich in Ti and poor in Be; the other one was rich in Be and poor in Ti. The Ti-rich phase was determined to be hexagonal (a ⳱ 0.536 nm, c ⳱ 0.888 nm) with space group P63/mmc.
I. INTRODUCTION
One way to design multicomponent metallic alloy systems with good glass-forming ability, such as ZrTiCuNiBe alloys1 is to combine binary and ternary systems of early (e.g., Zr, Ti, Hf) and late transition metals (e.g., Cu, Ni, Co) and simple metals (e.g., Be, Al) with deep eutectics and large differences of the atomic sizes for different alloy components. Such bulk metallic glasses show strong resistance against crystallization in the supercooled liquid state within a wide temperature range above glass transition. The Zr41Ti14Cu12.5Ni10Be22.5 bulk glass has been investigated intensively with respect to amorphous phase separation and crystallization during heat treatment2–7; however, only few investigations of the equilibrium phases exist.7,8 The aim of this work is to study the morphology, chemical composition, and structure of the crystalline phases after slow solidification of the Zr41Ti14Cu12.5Ni10Be22.5 alloy.
a)
Present address: Max-Planck-Institut fu¨r Mikrostrukturphysik Halle, Weinberg 2, 06120 Halle, Germany. b) e-mail: [email protected] J. Mater. Res., Vol. 15, No. 8, Aug 2000
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For composition analysis of the different phases of a heterogeneous microstructure, energy dispersive x-ray analysis in a transmission electron microscope (TEM/EDX) was applied successfully after careful sample preparation. As Be cannot be detected by EDX, an additional analysis by field ion microscopy with atom probe (FIM/AP) was carried out, which allowed a full analysis of all the components, even for very small crystals. X-ray diffraction (XRD) techniques for structure determination have
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