Analysis and control of microstructure of metal matrix composite under stress loading

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The present research aims at analyzing microscopic behavior of particles, matrix and their interfaces of particle reinforced metal matrix composites during static loading and making clear the effects of their fabricating processes on the behavior. The in situ tensile test in the scanning electron microscope equipped with a defromation stage was investigated at the first of all. As the result the test was successfully examined and it was possible to observe only microstructural degradation owing to structural defects under homogeneous stress distribution. It was also found that the same microstructural degradation was occurred inside the specimen as wel as that observed on its surface.Some Al_2O_3 and SiC particle dispersed aluminum alloy composites were produced with the powder extruding and melt stirring methods. The change in microstructure of the composites was observed continuously during tensile loading by the in situ tensile test. Some microcracks owing to the interface debonding and the particle fracture are initiated at early loading point before maximum loading in all composites. The microcracks do not propagate in the matrix because of its ductility, but the number of new microcracks are increased with inceasing strain. The character of the microcracks and their change are depend on the fabricating process of the composites.