Abstract:

The correlation between temperature and the content of interface reaction product ₄C₃ in carbon and graphite fibre reinforced aluminium precursors and the relation of the tensile strength of the precursors to the content of ₄C₃ and temperature are studied. The fractography of every precursor is analysed with SEM. The aluminium matrix of the precursors is dissolved with HC1 solution after thermal exposure at various temperatures, the surface of dealuminated fibres is examined and the tensile strength of the fibres is tested.The temperature at which the strength of precursors drops dramatically is about 75-100℃higher for Gr-Al than for C-Al （about 625 and 550℃ respectively）. The strengths both of the C-Al and Gr-Al precursors are very low at temperatures over 650℃ （30% and 40% of the room-temperature strength respectively）.The SEM analyses and tensile tests demonstrate that the decrease of precursor strength is prior to the surface damage of the fibres and the fibres may not be degrade by the interface reaction product ₄C₃ up to certain temperature. Only when a lot of ₄C₃ is formed, the remarkable deterioration of fibres can be observed and the strength of the precursors drops significantly too. Degradation of the fibres is merely one of the reasons why the strength of the precursors decreases. Moreover, it occurs only at higher temperature. Formation of ₄C₃, probably, changes the fracture model of the precursors.