THE EFFECT OF PROCESS VARIABLES ON THE STRUCTURE AND PROPERTIES OF ODS, y'- HARDENED NICKEL-BASE SUPERALLOYS

The purpose of this investigation is to obtain a fundamental understanding of the underlying mechanisms of coarse grain recrystallization of ODS, t" hardened nickel-based superalloys. Experiments have been carried out on a laboratory zone annealer using small bars in which a number of directional recrystallization (DR) speeds and temperatures were evaluated, enabling a 'process window' for satisfactory DR response to be established, on the basis of both structure and stress rupture properties. The influence of the thermal history associated with post extrusion thermomechanical processes on the recrystallization response has also been studied. Quenching experiments from a calibrated gradient zone annealing furnace have shown that nucleation of secondary recrystallization occurs at higher