*3.3. Hot Compression*

To verify the predictions of the calculated Zener pinning forces, hot compression tests were performed in the temperature range where the roughing passes would be expected to occur; i.e., 1150–1000 ◦C. The right cylinders were reheated to 1200 ◦C for two minutes and then cooled to various temperatures for recrystallization studies. The deformations were applied using an MTS-458 unit designed for deformation under constant true strain rate conditions equipped with a radiation furnace and a temperature controller. Glass lubricant was used to suppress barreling in the multiple hit, axisymmetric hot compression tests. If the pinning forces were low in the rough rolling range, then repeated recrystallization would be expected with accompanying grain refinement. On the other hand, if the pinning forces were high, then complete recrystallization would not occur, and the grain size would stay large, reflecting the reheated grain size, and the grain shape would not be equiaxed. Figure 6 shows an example of the thermomechanical path used in the first series of samples to closely simulate roughing passes in a typical hot rolled plate. Two reduction levels of 15% and 25% were used in this study and the strain rate (. ε) was set to be 10 s−<sup>1</sup> for all hot compression experiments.

**Figure 6.** Thermomechanical schedules used in hot compression deformations with 15% reductions.
