Microstructure and mechanical properties of hot-pressing chromium carbide/alumina nanocomposite prepared by MOCVD in fluidized bed

摘要

Nanocomposites of Cr_3C_2/Al_2O_3 were prepared by metali-organic chemical vapor deposition (MOCVD) method in a fluidized bed and sintered under hot-pressed condition at 1500 deg C forl h. The TEM microstructure showed that the Al_2O_3 matrix contained both intragranular and intergranular phase of Cr_3C_2. The hot-pressed Cr_3C_2/Al_2O_3 nanocomposites possessed better mechanical performance as regard to bending strength and fracture toughness in comparison to the monolithic Al_2O_3. The phenomenal change of the fracture mode from intergranular fracture of monolithic Al_2O_3 to transgranular fracture of nanocomposites is attributed to the enhancement of the residual stress and formation of a solid solution, eventually improving the strength of the Cr_3C_2/Al_2O_3 nanocomposite. Furthermore, it has been deciphered that the toughening mechanisms of the nanocomposites contribute to the crack deflection and the residual stress.