Plastic Deformation

At high temperatures (above about 1,200°C) alumina can deform by dislocation motion. The important paper by Merritt Kronberg [26], see also [1], p. 32, and [27], showed the details of dislocation motion in alumina. Basal slip on the close – packed oxygen planes is most common in alumina, with additional slip systems on prism planes.

Table 11 Torsional creep rates of some polycrystalline oxides at 1,300°C and 124 MPa applied stress (from [23], p. 755)

Material

Creep rate (X105 h 1)

AlA

0.13

BeO

30

MgO (slip cast)

33

MgO (pressed)

3.3

MgAl2O4, spinel (2-5 |im grains)

26

MgAl2O4 (1-3 pm grains)

0.1

ThO2

100

ZrO2

3