The development of microstructures and texture during the zone annealing of Ni-based ODS superalloy:Ma-600

Two extruded bars of the nickel based mechanically alloyed material MA-6000 have been zone recrystallized in a calibrated gradient furnace. A curved secondary recrystallization interface is observed, with the surface re crystallizing at a lower temperature than the interior. This is considered to arise indirectly from the strain gradients arising during extrusion. A < 110 > texture is present, and reasons for this are discussed. A progressive grain reorientation towards < 110 > has been measured behind the recrystallization interface. Quenching experiments have shown that nucleation of secondary recrystallization occurs at higher temperatures than that at which the recrystallization interface grows at the zoning speed employed. It is suggested that the microstructure develops by the thermally activated unpinning of interfaces which have mobility advantages. (author)