*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.