Nucleation mechanism of hetero-epitaxial recrystallization in wrought nickel-based superalloys

The mechanism of inverse precipitation of gamma-like shells forming around primary gamma' leading to heteroepitaxial recrystallization after thermomechanical processing was studied. The wrought nickel-based AD730 (TM) alloy was subjected to a sub-solvus heat treatment at 1050 degrees C and cooled at 5 degrees C/min in order to form heteroepitaxial gamma-like shells on primary gamma'. Electron backscattered diffraction analysis confirmed no measurable crystal misorientation between the gamma-like shells and primary gamma'. Atom probe tomography revealed segregation of Cr, Co and Fe at dislocations within the primary gamma', while the gamma-like shell was found enriched in these solutes compared to the gamma matrix. A mechanism rationalizing the inverse precipitation of gamma-like shells is proposed aiming to better understand the nucleation process of heteroepitaxial recrystallization in polycrystalline Ni-based superalloys. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

By studying the mechanism of inverse precipitation of gamma-like shells forming around primary gamma' after thermomechanical processing, a better understanding of the nucleation process of heteroepitaxial recrystallization in polycrystalline Ni-based superalloys can be achieved.