Creep in Brittle Ceramics Ductile at High Temperature Where Deformation is Possible

3 Creep in Brittle Ceramics (Ductile at High Temperature Where Deformation is Possible) 

It is important to also consider brittle materials in ceramics, since they deform at high temperatures. Deformation is essential for creep and, since ceramics are potential candidates for high-temperature applications during which deformation occurs, studies of creep and its retardation are important despite their RT brittleness. This discussion of creep will begin with single crystals, since no grainboundary sliding is involved and, thus, creep occurs only within the lattice. 

In Fig. 6.5, experimental transient creep is illustrated. This illustration represents commercially available SiC-fiber/calcium aluminosilicate matrix composites (Nicalon SiCJCAS-11). These composites contain 40 vol% Nicalon SiC fibers and had been hot-pressed. 

An experimental illustration of the strain-rate variation over time shown for the primary creep rate in Fig. 6.1b is presented in Fig. 6.6 for ceramics having the 

Fiber layup Loading history lOth (%) fiiootti (S ) Rcr.iooai (%) Rr.lOOth (%) 

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