Abnormal Grain Growth Mechanism of Calcium Hexaluminate Phase

Abstract

Calcium-hexaluminate phase(CA6) phase is known to be effective for the crack shielding due to the spinel block crystal structure. In this study, we focused to control the CA6 morphology for the good damage tolerance behavior in alumina and zirconia/calcium-hexaluminate(CA6) composites. calcium-hexaluminate(CA6) composites were prepared from zirconia, alumina and calcium carbornate powders. Calcium-hexaluminate(CA6) phase was obtained by the solid reaction through the formation of intermediate phase(CA2). CA6 phase showed column type abnormal grain grown behavior composed of small blocks. Due to the typical microstructure of CA6, alumina and zirconia/calcium-hexaluminate composites provide well controlled crack propagation behavior.

Thermal cycling behaviors of the plasma sprayed thermal barrier coatings of hexaluminates with magnetoplumbite structure

“…In the recrystallization process during thermal cycling, small platelet-like hexagonal grains are firstly formed, and then some of them would rearranged along their (0 0 0 1) faces to reach a lower energy position. 20,33,34 As shown in Fig. 8(a)-(d), some large platelets with a lot of small platelet-like grains located inside could be found in the fractured cross-section micrographs, which also happened for the LaMA coating.…”