%0 Journal Article
%T Comparison of Two Powder Processing Techniques on the Properties of Cu-NbC Composites
%A B. D. Long
%A R. Othman
%A Hussain Zuhailawati
%A M. Umemoto
%J Advances in Materials Science and Engineering
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/160580
%X An in situ Cu-NbC composite was successfully synthesized from Cu, Nb, and C powders using ball milling and high pressure torsion (HPT) techniques. The novelty of the new approach, HPT, is the combination of high compaction pressure and large shear strain to simultaneously refine, synthesize, and consolidate composite powders at room temperature. The HPTed Cu-NbC composite was formed within a short duration of 20£¿min without Fe contamination from the HPT¡¯s die. High porosity of 3¨C9%, Fe and niobium oxidations, from grinding media and ethanol during ball milling led to low electrical conductivity of the milled Cu-NbC composite. The electrical conductivity of the HPTed Cu-NbC composite showed a value 50% higher than that of milled Cu-NbC composite of the same composition. 1. Introduction Powder metallurgy (P/M) is the most common method for the synthesis of metal matrix composites (MMCs) [1¨C3], whereby the refinement and consolidation are the most important parts of this process. The refinement of powder particles leads to increasing mechanical strength of MMCs as given by the Hall-Petch relationship [4], as well as conferring excellent consolidation/high apparent density which enhances the properties of MMCs [5]. In addition, P/M shows many other advantages in the synthesis of MMCs such as homogeneous distribution of reinforcement in the matrix, fine grain size, synthesis process at low temperature, and cost saving. The excellent physical and mechanical properties of MMCs, in particular Cu-NbC composites, are applied widely in electrical fields such as electrodes for spot welding, contact materials in high power switches, sliding electrical contacts, and thermal management devices. In P/M, ball milling (BM) is well known as a powerful method to synthesize and refine MMCs with extremely fine and homogenous distribution of reinforcement in a metal matrix [6, 7]. However, BM imposes some disadvantages such as contamination from the grinding media and the process control agents (PCAs) during milling [6]. Cold compaction or cold isostatic pressing was used as a conventional consolidation method followed by sintering [8, 9]. However, these consolidation methods have a major problem which relates to a low density of the bulk material [9, 10]. Therefore, a second process such as hot extrusion, rolling, or forging was usually needed to completely consolidate the final product [11¨C13]. Previous research work [14] showed that increasing the density of Cu-NbC composite from 81 to 96.9% led to an increase in hardness and electrical conductivity by 3.4 and 5.8 times,
%U http://www.hindawi.com/journals/amse/2014/160580/