High temperature deformation and failure in aluminum-alumina particulate metal matrix composites

• Main Author: Ganguly, Partha
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/7778

This work was primarily concerned with investigating the role of the reinforcing particles on plastic flow and fracture of metal matrix composites (MMCs) in the high temperature, moderately high strain rate domain. Uniaxial tensile, uniaxial compressive, and collar compressive tests were conducted on as-cast and extruded MMCs (the uniaxial tests were also conducted on unreinforced AA6061), and the flow and fracture behavior of the materials examined. The micro-failure characteristics were ascertained through metallographic examination of the fractured samples - both perpendicular and parallel to the fracture surface, and through numerical simulations of the collar compression test on the as-cast MMC . The reinforcing particles were found to enhance the flow stress and lower the failure strain in these materials. The detrimental effect of the particles on failure strain was higher for the as-cast M M C - and this was deemed to be due to the presence of particle rich clusters in its microstructure. In both the extruded and as-cast MMCs, particle cracking and interfacial decohesion were the primary void nucleation mechanisms. The dominance of one mechanism over another was found to be temperature dependent - the former dominating at lower and the latter at higher temperatures. The MMC ductility peaked in the mid-temperature region, where the occurrence of the two mechanisms was comparable.