Formation of annealing twins during primary recrystallization of two low stacking fault energy Ni-based alloys

First stages of recrystallization are analyzed in low stacking fault energy nickel alloys cold rolled and subsequently annealed at 700 °C for 6 min. These alloys are envisaged as candidate materials for the heat exchanger of very high-temperature reactor that works at 1000 °C. First recrystallized grains show evidence of extensive twinning that is studied by transmission electron microscopy. Specific twinning features such as fivefold twin and microtwins bordered by partial dislocations are revealed. Twin density increases with increasing amounts of prior deformation before annealing. The local crystal orientations are determined at a nanometer scale. It is shown directly that when twinning occurs, the recrystallized area beyond the twin has a lower stored deformation energy. Thus, recrystallization and the associate twinning induce a decrease in the total stored deformation energy.