Fracture and Failure of Al-SiCpComposites at Different Temperatures and Conditions

Abstract

The fracture and failure behavior of extruded aluminum-silicon matrix alloy Al-7%Si-0.7%Mg (AlSi7) and composites reinforced with 10 and 20 vol.% SiC particles are investigated. The matrix alloy and composite samples are subjected to high-temperature tensile and thermal cycling tests above the temperature range from 25 to 430°C. At room temperature, the fracture surfaces reveal that failure modes consist of particle fracture, interface debonding, and void formation in the matrix within clusters of smaller particles oriented in the direction of extrusion. The evaluation of the microstructure shows that particle cracking-induced cavitation plays a more important role in the fracture of the composites at elevated temperatures than that at both room temperature and in thermal cycling tests. Scanning electron micrographs indicate that cracks are present in the composite samples under repeated action of the thermal cycling process. The failure mode of the thermally cycled composites is dominated by the presence of widespread cavitations and cracks (in the matrix), in a direction transverse to the applied stress, developed during extensive elongations. These are seen not only in the vicinity of the fracture surface but also in the regions far below the fracture tip of the sample.