Self-reinforced Ca-hexaluminate/alumina composites with graded microstructures

The physical, thermal, and mechanical characteristics of self-reinforced calcium-hexaluminate/alumina composites with a graded microstructure are described. The presence of CA6 phase in Al2O3 matrix has a significant effect on the physical, thermal, and mechanical properties of graded Al2O3–CA6 composites. The slightly lower shrinkage and density in the graded composite can be attributed to the presence of CA6 phase. The thermal expansion and densification behaviour of the graded composite showed that the presence of CA6 phase hinders the processes of sintering and densification of alumina matrix. When compared to the alumina region, the graded CA6–Al2O3 region is softer by virtue of the presence of the softer CA6 phase. However, the fracture toughness in the graded region is higher than the alumina region which can be attributed to the display of crack deflection and crack-bridging provided by the CA6 platelets.