The effect of deformation temperature on recrystallization in a Ni-based single crystal superalloys

Abstract

A series of experiments have been carried out to investigate the effect of deformation temperature on the recrystallization of nickel-based single crystal superalloys using isothermal (compression) and non-isothermal (directional solidification) deformation. The recrystallization features induced by accumulated plastic strain in two temperature ranges (1300–1150 °C and 600–400 °C) are distinctly different from that induced by deformation in one temperature range (1300–1150 °C). The different recrystallized features (area and number of grains) induced by isothermal deformation at temperatures ranging from room temperature to solidus can be attributed to different dislocation features, such as slip band, KW-lock, γ/γ' interfacial dislocations and Low Angle Boundary. Microscopic observations disclose that interactions of multiple slip systems have higher tendency of recrystallization. A close view between deformed and recrystallized samples of different deformation temperatures reveals that the critical kernel average misorientation (KAM) to induce recrystallization is about 0.4°. Furthermore, the number of recrystallized grains is proportional with the average KAM value based on the experimental measurements in a wide temperature range. Isolated recrystallized grains are observed at the stress concentration locations in the low plastic strain zone due to local high misorientation.