Microstructure evolution under high temperature deformation of CoNiCrAlY bond coat alloy

The evolution of microstructure and texture during high temperature uniaxial compressive deformation of two-phase (gamma+beta) 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 x 10(-3)s(-1) to 5.0 x 10(-4)s(-1) up to a true strain of -1.0. It was concluded that dynamic recrystallization (DRX) occurred in both gamma and beta phases, even in two-phase alloys. Under all deformation conditions, the main component of the texture in the gamma phase having fcc structure was {101}. As for the conditions of low Zener-Hollomon parameter Z in the gamma 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 beta phase with the B2 structure, the main component of the texture was {111}. Even under the low-Z conditions of the beta phase, the texture was not developed. Because the area fraction of the beta phase in CoNiCrAlY alloy is approximately 25%, and because the beta-phase grains were surrounded by gamma-phase grains, migration of the beta-phase grain boundaries should not occur.