Formation of GdAlO3-Al2O3 composite having fine pseudo-eutectic microstructure

GdAlO3 and Al2O3 powders were mixed and pulverised using ball mills. The prepared powder was spark plasma sintered at 1450 C without holding time. SEM showed a eutectic-like microstructure. The microstructure formed from a powder pulverised by a tumbling ball mill for one week was much finer than that by a planetary ball mill for 5 and 10 h. The fine homogeneous eutectic-like (pseudo-eutectic) microstructures could be formed at both eutectic and off-eutectic compositions. In case of crystallisation from a melt of eutectic components, homogeneous eutectic microstructures could be formed only at restricted compositions very close to the eutectic composition. Coarse primary crystals generally existed in the eutectic microstructure at off-eutectic compositions. The pseudo-eutectic microstructures could be formed at any composition because a mixing ratio of the starting powders could be varied. 24 refs.