Examination of recrystallization and grain growth of austenite with the photoemission electron microscope

Abstract

The recrystallization and grain growth of plain carbon steels has been examined using the technique of photoemission electron microscopy. The investigation has been carried out to determine why, in some instances, it is reported that an increase in the heating rate through and beyond the transformation range leads to a decrease in the austenite grain growth rate whereas in other instances an increase in heating rate through the critical region has led to an increase in the austenitic grain growth rate. This apparent contradiction may be resolved if the observed effects are considered in relation to a ‘breakaway temperature’ below which growth is difficult and so nucleation becomes the predominant factor in determining the final austenite grain size. Above any breakaway temperature growth becomes easier and dominates the situation. The final austenite grain size therefore depends on the heating rate through the critical region and the operating temperature.