Continuous observation of microstructural degradation during tensile loading of particle reinforced aluminium matrix composites

Abstract

The microstructural degradation of aluminium alloy composites by external tensile loading was continuously observed by in situ scanning electron microscopy tensile testing. The composites, which contained spherical Al₂O₃ and angular SiC particles, were prepared by the powder extrusion method. Some microcracks were initiated at small plastic strains after yielding in both composites by inteliace debonding and particle cracking. Angular particles generate microvoids at smaller strains than spherical particles. The microcracks do not propagate with increasing external loading because of the ductility of the matrix, but a number of new microcracks developed just before failure. Most microcracks are due to interface debonding rather than particle cracking. Many dimples on the matrix aluminium alloy are observed on some particles seen in the fracture surface, which proves that there is relatively strong bonding between the matrix and the particles in the composite produced by powder extrusion. However, part of the original surface observed on the debonded particles indicates that an incompletely bonded interface also exists in the composites.

MST /3111