Meta-Dynamic Recrystallization in the Ni-Based Superalloy Haynes 282

Abstract

Forging on an industrial scale often involves slow, size-limited cooling rates or high temperature hold times between, or after, deformation. This enables the dynamic recrystallization (DRX) initiated during forging to further progress under static conditions, a phenomenon called meta-dynamic recrystallization (mDRX). As mDRX will influence the final grain size, and thus properties, it is critical to understand and control it during processing. Here, we study the mDRX evolution in Ni-based superalloy Haynes 282 during post-deformation hold times of up to 120 s at 1080 °C after partial DRX. We find that mDRX is the dominating mechanisms responsible for the microstructure evolution the hold time. The very rapid mDRX kinetics in the initial stages suggest that quench delays (the time between the end of the deformation and the onset of the quenching intended to arrest the microstructure evolution) must be kept well below 1 s in order to allow reliable conclusions to be drawn from post-deformation microstructure investigations. A larger prior strain (larger DRX fraction) leads to faster mDRX kinetics and a larger final grain size. Larger strains leads to earlier impingement of the growing grains, which, in combination with smaller remaining deformed regions into which the grains can grow, limits the maximum size of the mDRX grains. We also note a close correlation between static recovery and stress relaxation during the hold time, whereas no such correlation between mDRX and stress relaxation can be observed.