Plastic deformation mechanisms in a crept L12 hardened Co-base superalloy

Plastic deformation mechanisms in a crept L12 hardened Co-base superalloy are investigated by transmission electron microscopy. The deformation happens mainly in the cobalt solid solution matrix by slip of ordinary a/2〈101〉{111} dislocations and rafting of the γ′ precipitates perpendicular to the external compressive stress axis is observed. Dislocation structures are early stages of the development of γ/γ′ interfacial dislocation networks. Furthermore, γ′ precipitates are sheared by partial dislocations generating stacking faults which sometimes extend over matrix channels and neighbouring γ′ precipitates. Due to the positive lattice mismatch at creep temperature the dislocation activity in matrix channels perpendicular to the compressive external stress axis is less pronounced compared to parallel channels.