Microstructure evolution under high temperature deformation of CoNiCrAlY bond coat alloy

Abstract The evolution of microstructure and texture during high temperature uniaxial compressive deformation of two-phase (γ+β) CoNiCrAlY bond coat alloy was investigated. Uniaxial compression tests were carried out at various temperatures ranging from 1073 K to 1473 K with true strain rates from 5.0 × 10 −3 s −1 to 5.0 × 10 −4 s −1 up to a true strain of −1.0. It was concluded that dynamic recrystallization (DRX) occurred in both γ and β phases, even in two-phase alloys. Under all deformation conditions, the main component of the texture in the γ phase having fcc structure was {101}. As for the conditions of low Zener-Hollomon parameter Z in the γ phase, the texture was not developed. This is due to the formation of twin boundaries during grain boundary migration which may weaken the texture. In the β phase with the B2 structure, the main component of the texture was {111}. Even under the low-Z conditions of the β phase, the texture was not developed. Because the area fraction of the β phase in CoNiCrAlY alloy is approximately 25%, and because the β-phase grains were surrounded by γ-phase grains, migration of the β-phase grain boundaries should not occur.