The temperature correction methods are described in details in previous research [30]. The final temperature difference was ± 5 K. The heating rate was maintained at 5 K/min to attain equilibrium at the experimental temperatures 1400 ℃, 1500 ℃, and 1600 ℃ for 72 h, respectively. The samples were quenched and dried after heat preservation, embedded in epoxy resin and polished. A schematic diagram of the experiment is shown in Fig. 1.