Electron microscopy and diffraction of ordering in Ni---W alloys

Mishra, NS and Ranganathan, S (1995) Electron microscopy and diffraction of ordering in Ni---W alloys. In: Acta Metallurgica et Materialia, 43 (6). pp. 2287-2302.

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Abstract

Electron microscopy and diffraction studies of ordering in stoichiometric Ni-20%W and off-stoichiometric Ni-15%W alloys have been carried out. The specimens of Ni-20%W were first disordered at 1398 K for 4 h and then quenched rapidly into water. Short range order (SRO) spots were observed at {1 1/2 0}* positions. Two hitherto unknown metastable phases: D-2h(25)-Ni2W and DO22-Ni3W were observed in the diffraction patterns. Long range order (LRO) transformations were studied at 1103 and 1213 K. Kinetics and mechanism of transformations have been identified. Ni-15%W specimens were solution treated at 1523 K for 1 h followed by quenching in water. SRO spots similar to those found in Ni-20%W were observed in this alloy as well. The transition to LRO was studied at 1093 K. Distinct Ni4W precipitates could be observed after 5 h of annealing at this temperature. After 100 h of annealing precipitates were found to grow into faceted shape coherent with the disordered matrix. After prolonged annealing for over 150 h the Ni4W precipitates began to lose coherency by the generation of misfit dislocations. The microstructural observations have been compared for the stoichiometric and off-stoichiometric alloys.

Item Type:	Journal Article
Publication:	Acta Metallurgica et Materialia
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	19 May 2011 04:55
Last Modified:	19 May 2011 04:55
URI:	http://eprints.iisc.ac.in/id/eprint/37713

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