SOME CHARACTERISTICS OF THE FATIGUE FRACTURE OF A KIND OF Al₂O₃·SiO₂f /ZL108 COMPOSITE MATERIAL

The fatigue behaviour of the Al₂O₃·SiO₂ fibre reinforced aluminum matrix composites produced by the squeeze casting method was investigated. The fatigue crack initiation and propagation were observed by SEM. It is found that the initiation of fatigue cracks is originated from different areas. The fatigue crack growth in the form of linking main cracks with the voids, formed at the tip of cracks, or in a discontinuous manner follows a fibre and shots concentrated path. During the fatigue process, the formation of the main crack expends most of the whole fatigue life, and once the main crack forms, the crack propagates rapidly and fractures immediately. It is believed that Al₂O₃·SiO₂f /ZL108 composites show a characteristic of brittle fracture macroscopically, but the matrix of the composites still shows more ductility in microscopic characteristics.