Effect of twin nucleation and twin on the recrystallization of a nickel-based superalloy during hot compression

Abstract

The nucleation mechanism of deformation twin (DT) and annealing twin (AT), and the effect of twins on recrystallization were studied comprehensively for Nickel-based superalloys during dynamic recrystallization (DRX). The aim is to improve the understanding of microstructure evolution during hot deformation. Hot compression tests were carried out at the temperature of 900-1150 °C with the strain rate of 0.01-1 s -1 for a Nickel-base superalloy. The results show that the DT and the Ʃ3 boundary exist simultaneously in the DRX stage. DTs are nucleated by the rotation of Franck partial dislocations and the decomposition of perfect dislocations. The DTs hinder the movement of dislocations in deformed grains and promote the nucleation of DRX grains. Ʃ3 boundaries associated with stacking faults are formed at recrystallized grain boundaries. In the condition of continuous DRX (CDRX), the Ʃ3 boundary changes the grain orientation and restrain the CDRX nucleation. While for the discontinuous DRX (DDRX), the Ʃ3 boundary provides an additional nucleation site and increase the nucleation rate. In addition, the comprehensive effect of DTs and ATs can promote the DRX nucleation, for which increase at first and then decrease with nucleation mechanical transform from CDRX to DDRX. • Deformation twins are nucleated by the rotation of Franck partial dislocations and the decomposition of perfect dislocations. • The quantity of deformation twins decreasing with the increase of DRX volume fraction. • Deformation twins hinder the movement of dislocations and promote the nucleation of CDRX. • The Ʃ3 boundaries hinder the CDRX nucleation and accumulate the DDRX nucleation process.