Role of the grain-boundary phase on the elevated-temperature strength,toughness, fatigue and creep resistance of silicon carbide sintered with Al,B and C |
| |
Affiliation: | 1. College of Sciences, Shanghai University, Shanghai 200072, PR China;2. Center for Thorium Molten Salt Reactor System, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, PR China;3. School of Materials Science and Engineering, Shanghai University, Shanghai 200072, PR China |
| |
Abstract: | The high-temperature mechanical properties, specifically strength, fracture toughness, cyclic fatigue-crack growth and creep behavior, of an in situ toughened silicon carbide, with Al, B and C sintering additives (ABC-SiC), have been examined at temperatures from ambient to 1500°C with the objective of characterizing the role of the grain-boundary film/phase. It was found that the high strength, cyclic fatigue resistance and particularly the fracture toughness displayed by ABC-SiC at ambient temperatures was not severely compromised at elevated temperatures; indeed, the fatigue-crack growth properties up to 1300°C were essentially identical to those at 25°C, whereas resistance to creep deformation was superior to published results on silicon nitride ceramics. Mechanistically, the damage and shielding mechanisms governing cyclic fatigue-crack advance were essentially unchanged between ~25°C and 1300°C, involving a mutual competition between intergranular cracking ahead of the crack tip and interlocking grain bridging in the crack wake. Moreover, creep deformation was not apparent below ~1400°C, and involved grain-boundary sliding accommodated by diffusion along the interfaces between the grain-boundary film and SiC grains, with little evidence of cavitation. Such unusually good high-temperature properties in ABC-SiC are attributed to crystallization of the grain-boundary amorphous phase, which can occur either in situ, due to the prolonged thermal exposure associated with high-temperature fatigue and creep tests, or by prior heat treatment. Moreover, the presence of the crystallized grain-boundary phase did not degrade subsequent ambient-temperature mechanical properties; in fact, the strength, toughness and fatigue properties at 25°C were increased slightly. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|