Directional recrystallization by zone annealing in a Ni-based ODS superalloy

For new Ni-base ODS superalloy manufactured by mechanical alloying, zone annealing experiment was implemented with parameters of temperature and hot zone velocity in order to develop the directionally recrystallized columnar grains. The progressive growth front of the columnar grains is synchronized with the hot zone movement, and columnar grains in millimeter scale were accomplished by appropriate hot zone velocity. This is secondary recrystallization through preferentially abnormal grain growth of the primarily recrystallized grains with the texture of cube orientation (001)[01¯0] as well as Goss orientation (110)[001]. The growth rate of the columnar grains estimated by using the grain boundary energy (ΔGgb) of the primarily recrystallized grains, pinning force by oxide particles (ΔGpin) and mobility of the grain boundary is relatively comparable to the hot zone velocity. The steep temperature gradient ahead of hot zone is substantially critical to keep the small size of the primarily recrystallized grains that lead to higher driving force for columnar grain growth due to the large grain boundary stored energy. •The grain boundary energy of the primarily recrystallized grains and pinning force by nano-size oxide particles were estimated.•The criteria to create the directionally recrystallized grains and their formation mechanism were clarified.•The key parameter to accelerate the formation of the directionally recrystallized grains was proposed at first.