KINETICS OF GRAIN-GROWTH IN ANORTHITE

We investigated the grain growth kinetics of synthetic pure anorthite aggregates. The starting material was prepared from glass and has a ho mogeneous starting grain size of 3-4 mu m. Porosity was less than 1% a nd the dislocation density was less than 2 x 10(7) cm(-2). The samples were subsequently annealed at temperatures between 1100 degrees C and 1350 degrees C in air from 10 min to 480 h. Grain size was determined optically. We observed normal grain growth for anneals less than 24 h . The grain growth exponent n varied between 2.5-2.7 for different tem peratures. We determined the activation energy for grain growth to be 365 +/- 25 kJ/mol. Microstructural observations show a decrease in asp ect ratio of the grains from 2.8 to 1.7 with increasing annealing temp eratures and duration.