Development of microstructure during creep of polycrystalline mullite and a nanocomposite mullite/5vol.% SiC

Defocus convergent beam electron diffraction analysis of dislocations in mullite

“…It may be noted that these experimentally determined Burgers vectors correspond to perfect lattice translations. Stacking faults have not been observed in this mullite material, neither in the as‐sintered condition nor after creep testing (Gustafsson et al , 2002, 2009). This indicates that partial dislocations are unlikely to form in the mullite structure.…”

“…This indicates that matrix dislocations are mobile and are able to form low‐energy configurations. Considering the reports on the deformation behaviour of mullite, however, the contribution from glissile dislocations to plastic deformation seems to be limited (Dokko et al , 1977; Hynes & Doremus, 1991; Gustafsson et al , 2002, 2009).…”

“…Detailed descriptions of the fabrication procedure and the mullite ceramic microstructure are given in separate publications (Gustafsson et al , 2002, 2009).…”

“…Despite the extensive research on mullite (Aksay et al , 1991), there is no conclusive information on the slip systems and the Burgers vectors of dislocations. Investigations of the mechanical properties of mullite ceramics have indicated that mullite is comparatively resistant to plastic deformation by dislocation glide (Dokko et al , 1977; Okamoto et al , 1990; Aksay et al , 1991; Hynes & Doremus, 1991; Gustafsson et al , 2002, 2009). Transmission electron microscopy (TEM) of polycrystalline mullite subjected to creep tests in compression, or in tension, showed only a limited increase in dislocation density after creep deformation (Hynes & Doremus, 1991; Gustafsson et al , 2002, 2009).…”

Microstructural development and mechanical performance of mullite-alumina and hibonite-alumina ceramics with controlled addition of a glass phase

“…Creep resistance of the mullite composites is outstanding. Deformations higher than 0.25% are expected in mullite composites with less than 10 % mullite [19,[23][24][25]. It is clear that a higher mullite content influences the creep behaviour.…”