The effect of heating rate on the recrystallization behavior of high gamma', ods superalloys

Directional recrystallization is an essentail step in the production of ODS nickel-based alloys with high gamma'-content, such as MA 6000 and MA 760. The rate of heating to the recrystallizationtemperature plays an important role for the final grain structure. This can be explained by the development of a certain "primary" grain size during the heating period.An additional aspect is the existence of heating rate limits, which determine the success of the recystallization. The existence of a critical minium heating rate (T min) is related to normal grain growth, which reduces the driving force for subsequent abnormal grain growth. Surprisingly, recent investigations have also revealed in some cases the occurrence of a ritical maximum heating rate (T max). In this paper an attempt is made to explain this new phenomenon, which may have important practical implications, through the formation of different carbide phases