Experimental and numerical study of grain growth in alumina fibres heat treated at 1700°C

The studied material is an alumina fibre acting as a reinforcement in a NiAl/Al2O3 composite. The processing of this composite involves a 1700 degrees C heat treatment. Grain growth phenomena taking place within the fibre during that step ape investigated. Above 1600 degrees C, the size of the grains reach the fibre diameter for a 1 h heat treatment. Further morphological evolution is discussed using thermodynamic calculations. Taking into account the presence of the liquid alloy, a deepened grain boundary groove is predicted and experimentally observed. The second part of this work deals with grain growth modelling during the hearing and cooling steps. A cubic grain growth kinetics law is found and is used to predict final grain sizes as a function of heating and cooling rates. (C) 1999 Elsevier Science Limited. All rights reserved.