Metadynamic Recrystallization and Grain Growth During Ingot-to-Billet Conversion of a Ni-Based Superalloy: JMAK Modeling and Experimental Validation
摘要
The metadynamic and short-time grain growth development during the conversion of Ni-base alloy 680 ingot was evaluated by performing isothermal compression tests and post-forging holds on a Gleeble® (GLEEBLE® is a registered trademark of Dynamic Systems) 3800 thermal–mechanical simulator and implemented as a JMAK model of microstructure evolution. Incomplete dynamic recrystallization (DRX) at lower temperatures creates partially recrystallized microstructures which may fully recrystallize by metadynamic recrystallization (MDRX). Recrystallized grains may then grow via short-time grain growth while the material remains at forging temperature. These phenomena are critical to understanding the recrystallization process during hot forging and to design a forging process that generates a fully recrystallized microstructure during manufacturing. Temperature plays a critical role in this process as temperatures above 1038 °C are sufficient to achieve a fully recrystallized microstructure during DRX, while it is often incomplete below that temperature such that full recrystallization is only achieved through MDRX. During post-forging holds, the short-time growth of recrystallized grains is minimal at or below 1038 °C and more significant at or above 1093 °C. Blind validation for untested forging conditions shows that the model captures the MDRX kinetics well but overpredicts the grain growth kinetics except at high temperatures.