Further evidence for diffusional creep in fine-grained two-phase Al_2O_3-Y_3Al_5O_(12) materials

摘要

It was recently suggested that the creep behaviour of fine-grained two-phase Al_2O_3-Y_3Al_5O_(12) (matrix) materials in the temperature range 1400 to 1500C under applied stresses between 3 and 20 MPa was controlled by a diffusional creep mechanism [1]. Evidence to support this suggestion was based on the floowing: (i) fine grain size (L, linear intercept grain size, =3-10 um); (ii) a short primary creep stage (strain, e<0.02); and (iii) stress exponent, n, close to unity (n=1.1). A comparison of the activation energy for creep for the two-phase Al_2O_3-Y_3Al_5O_(12) materials with the activation energy for creep for the single-phase materials and the activation energy for diffusion lead to the conclusion that the creep behaviour of the Al_2O_3-Y_3Al_5O_(12) materials was controlled by Nabararo-Herring [2,3] rather than Coble [4] diffusional creep.