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COMPOSITES SCIENCE AND TECHNOLOGY Composites Science and Technology 64 2004 1539 1549 www elsevier com locate compscitech Damage accumulation and mechanical properties of particle reinforced metal matrix composites during hydrostatic extrusion D J Lahaie a J D Embury a F W Zok a b Department of Materials Science and Engineering McMaster University 1280 Main St W Hamilton Ont Canada L8S 4L7 b Department of Materials College of Engineering III University of California Santa Barbara CA 91306 5050 USA Received 16 July 2003 received in revised form 31 October 2003 accepted 12 November 2003 Available online 17 January 2004 Abstract The e ects of hydrostatic extrusion on particle cracking and on the subsequent tensile properties of some prototypical particlereinforced metal matrix composites are investigated In most cases tensile failure occurs through a plastic instability in accordance with the Considere criterion for necking The corresponding failure strain is therefore dictated by the global ow and hardening characteristics of the composites as in uenced by the intrinsic ow properties of the matrix as well as the extent and rate of particle cracking Such cracking leads to signi cant reductions in the hardening rate and thus causes a reduction in the failure strain relative to that of the neat matrix alloy Extrusion prior to tensile testing has the e ect of saturating the ow stress of the matrix and limiting the tensile ductility to low values largely because of the very low hardening rate of the matrix Particle cracking during extrusion causes a further reduction in ductility The dominant role of the matrix hardening is demonstrated through re tempering treatments of extruded billets prior to tensile testing A micromechanical model of particle cracking is developed taking into account the e ects of both the hydrostatic and the deviatoric stress components in axisymmetric loadings The model is used to rationalize the observed trends in damage accumulation with particle



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