Role of the inter-pass cooling rate in recrystallization behaviors of Ni-based superalloy during interrupted hot compression

Abstract

The microstructural evolution of a Ni-based superalloy under interrupted hot compressive deformation with different cooling rates in the inter-pass stage is investigated. It is found that metadynamic recrystallization (MDRX) in the inter-pass stage is more sensitive to the accumulated strain than the deformation temperature which is above the recrystallization temperature. The variations of both the grain distribution and the texture intensity caused by MDRX during the inter-pass stage result in variations of the yield stress (YS) and the work hardening (WH) rate in each stage. Results also show that the MDRX process in the inter-pass stage has a considerable influence on the final microstructure of three-pass compression. The final grain distribution is more uniform, and the compression texture gradually transforms into recrystallization texture with an increasing degree of MDRX. In order to predict the MDRX fraction in the inter-pass cooling stage, a modified kinetic equation is established, which can reasonably predict the MDRX behavior under multi-pass compression with different conditions in the inter-pass stage. Meanwhile, the influence of the inter-pass cooling stage on the mechanism of dynamic recrystallization (DRX) is studied. It is universally acknowledged that the discontinuous dynamic recrystallization (DDRX) process is the major deformation mechanism for the Ni-based superalloy. However, the continuous dynamic recrystallization (CDRX) process is promoted in the compression stage with a decrease of the cooling rate in each inter-pass stage.