Creep and Microstructural Evolution at High Temperature of Liquid‐Phase‐Sintered Silicon Carbide

Abstract

The compressive creep characteristics at 1625°C of liquid‐phase‐sintered silicon carbide ceramics containing 5 and 15 wt% of crystalline Y3Al5O12 (YAG) as the secondary phase were studied. In the two cases, strains between 10% and 15% were reached without failure. The creep behavior was characterized by a stress exponent n≈2, and the proportion of secondary phase was related to the creep resistance of the materials. The microstructural evolution during creep consisted firstly in the re‐distribution of the secondary phase, probably as a consequence of its viscous flow at the creep conditions, and secondly an extensive nucleation and growth of cavities, which was more important for the highest YAG content. The latter reflects the carbothermal reduction that the secondary phase undergoes during creep.

Effect of microstructure on the mechanical properties of liquid-phase-sintered silicon carbide at pre-creep temperatures

“…4,8,9,20,21 Thus, despite the usual working temperatures of SiC being in the intervening temperature range, this interval has been somewhat neglected in previous studies, with the exception of certain measurements of the dynamic elastic modulus. 22 The present work seeks to redress this deficiency by elucidating the role of microstructural variables such as grain size, grain aspect ratio, and content of the intergranular phase on the mechanical properties of LPS-SiC in this intermediate temperature range.…”

Effect of Porosity on Structure, Young's Modulus, and Thermal Conductivity of SiC Foams by Direct Foaming and Gelcasting

“…As far as the densification of SiC is concerned, the foams prepared by these techniques are mainly sintered either in the presence of high‐temperature liquid phase or reaction sintering process . The SiC framework consolidated by liquid phase sintering or reaction bonding has limitations in terms of their high‐temperature thermo‐mechanical properties . Conversely, SiC ceramics densified in the presence of B and C as solid‐state sintering additives possess great potential in terms of its superior high‐temperature properties .…”

Thermal stress relaxation creep and microstructural evolutions of nanostructured SiC ceramics by liquid phase sintering

“…According to this viscous flow mechanism, the amorphous phase is squeezed out from intergranular grains under tensile tension and accumulates in multigrain pockets. 7 Consequently, the flow of the amorphous phase can explain the appearance of large pockets of amorphous phase and relatively regions of interlocked grains depleted of amorphous phase with the significant growth of SiC grains, as shown in Fig. 8.…”

“…In their opinions, the decomposition of YAG was accompanied by the formation of aluminum-containing gaseous species with the reactions between YAG and gaseous CO, resulting in the decrease of Al content. 7,14,21 The source of gaseous CO is sufficiently produced by the active oxidation of SiC under low oxygen partial pressure:…”

“…In particular, the oxide remains are anticipated to impose deleterious effects on the creep resistance. [5][6][7] Besides, major load to be imposed on structural materials is thermal stress for these applications. The stress relaxation behavior under deformationcontrolled stress should be primarily clarified.…”