| The development of commercial applications for particle-reinforced metal matrix composites has been inhibited due to low ductility, despite improved strength, stiffness, and wear resistance. This low ductility is caused by the addition of the brittle second phase particles, which act as void nucleation sites during loading.; Damage evolution in metal matrix composites is known to occur through particle cracking, particle-matrix decohesion, or damage nucleation inside particle clusters. It is possible to effectively eliminate particle cracking and significant particle clustering through the use of small particles and a powder-processing production route. In a powder-processed, small-particle metal matrix composite, particle-matrix decohesion is known to be the controlling damage mechanism.; It is difficult to effectively study microstructural damage evolution in metal matrix composites due to artefacts arising from traditional metallographic sample preparation techniques. The sectioning and imaging capabilities of the focused ion beam microscope provide an excellent method for studying damage accumulation in metal matrix composites.; The capabilities of the focused ion beam system have been used to carry out a study of damage evolution in a powder-processed/hot-extruded Al2080/SiC p metal matrix composite. Microvoid damage is found to be accurately preserved during FIB sectioning, allowing several measurements of damage evolution during tensile loading. These microscopic damage measurements are correlated with the macroscopic damage parameter, D, as determined by density measurements.; Using transmission electron microscopy, the microstructural damage evolution at the SiC-matrix interfaces has been examined. Particle-matrix decohesion was seen to occur along an amorphous interfacial layer, while microcracks in the small SiC particles were seen to occur beyond a critical strain level. |
