| Summary: | 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. === Applied Science, Faculty of === Materials Engineering, Department of === Graduate
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