Superdislocations activated by 1200 °C creep in Ni3Al phase of a single crystal superalloy: Non-coplanar configuration and motion model

Superdislocations in Ni 3 Al precipitates of single crystal (SX) superalloys are activated during ultra-high temperature creep, but such dislocations' configuration and possible motive mode remains unclear. In this paper, we systemically analysis the microstructure of a model SX superalloy after 116 h ultra-high temperature stress-rupture test under the condition of 1200 °C/80 MPa. The γ′ precipitates are highly rafted and dense dislocation networks are constructed at the γ/γ′ interface after high temperature crept. Using high-tilt transmission electron microscope (TEM), two kinds of superdislocation in the γ′ phase with Burgers vector b = [001] and b = [110] are verified to exhibit a 3D non-coplanar configuration. These superdislocations in γ′ phase are formed by the combination of two a/2<110> dislocations with different Burgers vectors. The non-coplanarity assumes γ′-dislocation climbing mode has been activated to produce plastic deformation. These results give new understanding of plasticity micro-mechanism of Ni 3 Al precipitates against ultra-high temperature and helps developing advanced superalloys resisted to elevated temperature.