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Advances in Materials Science and Engineering
Volume 2014, Article ID 617241, 8 pages
http://dx.doi.org/10.1155/2014/617241
Research Article

Nanocrystalline Al Composites from Powder Milled under Ammonia Gas Flow

1Metallurgy and Materials Engineering Group, Escuela Técnica Superior de Ingeniería, University of Seville, Camino de los Descubrimientos s/n, 41092 Sevilla, Spain
2Department of Chemistry and Materials Science, Escuela Técnica Superior de Ingeniería, University of Huelva, Campus La Rábida, Carretera Palos s/n, Palos de la Frontera, 21819 Huelva, Spain

Received 22 October 2013; Revised 14 January 2014; Accepted 15 January 2014; Published 27 February 2014

Academic Editor: Denis Chaumont

Copyright © 2014 J. Cintas et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The production of high hardness and thermally stable nanocrystalline aluminium composites is described. Al powder was milled at room temperature in an ammonia flow for a period of less than 5 h. NH3 dissociation during milling provokes the absorption, at a high rate, of nitrogen into aluminium, hardening it by forming a solid solution. Controlled amounts of AlN and Al5O6N are formed during the subsequent sintering of milled powders for consolidation. The pinning action of these abundant dispersoids highly restrains aluminium grain growth during heating. The mean size of the Al grains remains below 45 nm and even after the milled powder is sintered at 650°C for 1 h.