Structural Evolution and Phase Stability of Hume-Rothery Phase in a Mechanically Driven Nanostructured Ag-15 at. pct Sn Alloy

Chithra, S and Malviya, KD and Chattopadhyay, K (2014) Structural Evolution and Phase Stability of Hume-Rothery Phase in a Mechanically Driven Nanostructured Ag-15 at. pct Sn Alloy. In: METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 45A (3). pp. 1148-1160.

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Abstract

The paper reports phase evolution in mechanically driven Ag-15 at. pct Sn alloy powder starting with elemental powders in order to establish the feasibility of designing nanocomposites of a Ag-Sn solid solution. This alloy lies in the phase field of the hexagonal zeta-phase which is a well-known Hume-Rothery electron compound with an electron-to-atom ratio of about 1.45 and hexagonal crystal structure (a = 0.2966 nm, c = 0.4782 nm). Through a systematic use of X-ray diffraction and transmission electron microscopy, the results establish the formation of the zeta-phase which co-exists with the Ag solid solution during the initial phase of milling. Mechanical milling for long duration (55 hours) destabilizes the zeta-phase. A complete solid solution of Ag with a grain size of similar to 8 nm could be achieved after 60 hours of milling. Additional milling can induce decomposition of the solid solution that results in a reappearance of zeta-phase. We present a detailed thermodynamic calculation which indicates that complete Ag solid solution of the present alloy composition would be possible if the crystallites size can be reduced below a certain critical size. In particular, we show that both Ag and zeta-phase grain sizes need to be taken into account for determining the metastable equilibrium and the phase change that has been experimentally observed. Finally, we argue that recrystallization processes set a limit to the achievable size of the nanoparticles with metastable Ag solid solution.

Item Type:	Journal Article
Publication:	METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
Publisher:	SPRINGER
Additional Information:	copyright for this article belongs to SPRINGER, 233 SPRING ST, NEW YORK, NY 10013 USA
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	26 Mar 2014 07:38
Last Modified:	26 Mar 2014 07:38
URI:	http://eprints.iisc.ac.in/id/eprint/48715

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