Effect of heating rate on grain morphology of in situ reinforced reaction bonded aluminium niobate-based composites

Reaction-bonded aluminium niobate-based composites with tailored microstruc tures were fabricated through controlled nucleation and growth of AlNbO4 ne edle-like grains. Using heating rates of 0.5 to >160 degrees C min(-1), the effects of heat-up period on microstructure development, and the volume co ntent, grain-size distribution as well as aspect ratio of AlNbO4 grains has been investigated. The morphology of the final microstructure is principal ly determined by the grain growth during heat-up. Equiaxed to elongated gra ins were obtained by using different heating rates and thermal ageing at 13 20 degrees C in air. SEM observations revealed that increasing the heating rate promotes the development of large and homogeneously distributed needle -like grains. The results presented show that tailoring of final AlNbO4 mic rostructures become possible by the control of heating rate. (C) 1999 Kluwe r Academic Publishers.