Regulation of phase evolution of CaAl12O19 on properties of in-situ formed MgAl2O4-CaAl12O19 composites

The in-situ formed MgAl(2)O(4)eCaAl(12)O(19) (MAeCA(6)) composites were fabricated in this study. To clarify the influence of the evolution of CA(6) phase on the properties of MAeCA(6) composites, the sintering temperature was carried out at 1200-1700 degrees C for 2 h. The results show that the growth and development of CA(6) grains improves the densification and flexural strength of MAeCA(6) composites. The formation of MA phase occurs at 1200 inverted perpendicular C, while the CA(6) phase is formed by the reaction of CaAl4O7 (CA(2)) and Al2O3 appears at 1400 degrees C. The plate-like CA(6) grains intersect with each other, presenting regular hexagonal morphology with a high aspect ratio at 1500 degrees C. The CaOeAl(2)O(3)eSiO(2) phase acts as an interface phase to regulate the growth and development of MA and CA(6) grains. The CA(6) phase was crystallized from the transient liquid phase CaOeAl(2)O(3)eSiO(2) to significantly increase its thickness at 1600 degrees C. At the same time, as the sintering temperature rises, the apparent porosity of the sample decreases from 24% at 1400 degrees C to 4% at 1600 degrees C, and the flexural strength correspondingly increases from 96.6 MPa to 167 MPa. However, the suitable sintering temperature should not exceed 1600 degrees C for better properties of the composites. (C) 2021 The Author(s). Published by Elsevier B.V.