Effects of post-sintering annealing on the microstructure and toughness of hot-pressed SiCf/SiC composites with Al2O3-Y2O3 additions

• Published in: Ceramics international Vol. 43; no. 16; pp. 13330 - 13338
• Main Authors: Fitriani, Pipit, Yoon, Dang-Hyok, Sharma, Amit Siddharth
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2017
• Subjects: Ceramic matrix composites; Flexural strength; SiC; Toughness and toughening; Ceramic matrix composites; Toughness and toughening; SiC; Flexural strength
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2017.07.031

This study examined the effects of post-sintering heat treatment on enhancing the toughness of SiCf/SiC composites. Commercially available Tyranno® SiC fabrics with contiguous dual ‘PyC (inner)-SiC (outer)’ coatings deposited on the SiC fibers were infiltrated with a SiC + 10wt% Al2O3-Y2O3 slurry by electrophoretic deposition. SiC green tapes were stacked between the slurry-infiltrated fabrics to control the matrix volume fraction. Densification of approximately 94% ρtheo was achieved by hot pressing at 1750°C, 20MPa for 2h in an Ar atmosphere. Sintered composites were then subjected to isothermal annealing treatment at 1100, 1250, 1350, and 1750°C for 5h in Ar. The correlation between the flexural behavior and microstructure was explained in terms of the in situ-toughened matrix, phase evolution in the sintering additive, role of dual interphases and observed fracture mechanisms. Extensive fractography analysis revealed interfacial debonding at the hybrid interfaces and matrix cracking as the key fracture modes, which were responsible for the toughening behavior in the annealed SiCf/SiC composites.