Recrystallization (RX) has been regarded as one of the major difficulties encountered in the manufacture of the single crystal components. High-angle grain boundaries induced by the formation of RX degrade the mechanical properties dramatically [1,2], and may even induce catastrophic failure during service. The present study is focused on two questions: (1) is there a critical strain during directional solidification that can induce RX? and (2) is it possible to predict the RX sensitivity of an alloy? Single crystal castings (solid and cored) with platforms are prepared. RX appears at all fillet radii under the platforms of the solid castings, while no RX is observed in cored castings after heat treatment. Microstructure observation and stress/strain simulation indicate that RX is induced by high temperature plastic deformation. The critical plastic strain to induce RX is about 3.5-4% with a vulnerable temperature range between 1150-1300 °C [3]. The orientation and microstructure evolution in a single crystal superalloy deformed at different temperature with a plastic strain around 4% are then studied, and correlated to the RX behaviors (Fig. 1). It is interesting to see that RX generally occurs at a KAM value above ~0.4o, independent of the deformation temperature. The possibility of a method to predict the RX sensitivity of a single crystal alloy is then discussed based on these results.

References
[1] G. Xie, L. Wang, J. Zhang, L.H. Lou Meter. Mater. Trans. A, 2008, 39, 206.
[2] J.J. Moverare, S. Johansson, R.C. Reed Acta Mater., 2009, 57, 2266.
[3] W. Xiong, Z. Huang, G. Xie, Y. Lu, W. Zheng, L.H. Lou, J. Zhang Meter. Mater. Trans. A, 2022, 53, 1585.