*Note: Value has been calculated through the relation ofδ SD S/δD B=0.001.
Fig. 2a shows the relationship between σ n and
cavity growth rate at three different temperatures of 500/550/600 ˚C, as
predicted by Eq.(4). The cavity growth rate increases by one order of
magnitude with temperature increasing from 500 to 600 ˚C. However, the
transition value of σ n (~400
MPa), which differentiates the cavity growth mechanism under low and
high stresses, is not affected by the temperature. This is as expected
because the GB diffusion has the same activation energy as the surface
diffusion (Table 1). Effects of the radius r andσ n on cavity shrinkage rate are shown in a
contour plot of Fig. 2b, as predicted by Eq.(6). Different colours
signify temperatures of 500/550/600 ˚C, respectively. For each
temperature, the contour curves with the largest value are always
towards the top left, indicating that a higher compressive stressσ n or smaller cavity radius r results in a
higher shrinkage rate. By comparing different coloured curves with the
same value, the shrinkage rate is found to be positively correlated with
temperatures.