FRACTURE-BEHAVIOR OF A SIC-PARTICLE-REINFORCED ALUMINUM-ALLOY AT HIGH-TEMPERATURE

The fracture behaviour of a composite based on 7075 aluminium alloy wa s studied under uniaxial tensile loading in the temperature range 25-4 00 degrees C at a strain rate of 10(-3) s(-1). The ductility of the co mposite was found to be much lower than that of the monolithic alloy a t all temperatures, but both materials exhibited similar strength leve ls above 300 degrees C. Particle fracture was the main damage mechanis m prior to final fracture at room temperature while interface debondin g together with interparticle voids were dominant features in fracture at high temperature. Large particles and regions of clustered particl es were found to be the locations prone to damage in the composite at both room and high temperatures. At room temperature, particle fractur e was observed at clusters of particles as well as in large particles, whereas at high temperature voids nucleated in the matrix closely adj acent to particles and at particle ends. This can be attributed to the high local stress in these regions and the high probability of flaws in large particles. It was also found that the internal damage associa ted with particle clusters was in regions below the fracture surface a nd that the extent of damage in the reinforced alloy increased with in creasing temperature. (C) 1998 Elsevier Science Ltd. All rights reserv ed.