Hot compression test was carried out at 1000 ~C to investigate the dynamic recrys- tallization nucleation mechanism of a nickel-base superalloy. It was found that the bulging of original grain boundaries was inhibited by carbides and deformation twins at the boundaries. Recrystallized nuclei evolved from the subgrains of dislocation re- configuration along original grain boundaries, and the growth of the potential nuclei was carried out by the coalescence of subgrains. The necklace structure of recrys- tallized grains along original grain boundaries was attributed to the strain gradient from grain boundary to grain interior.
The microstructure and precipitation characteristics of 22Cr-14W-2Mo superalloys added with various La contents have been studied by SEM, TEM and EDX.It is found that the carbides are refined by adding La.M23C6 carbides inside the grain in a diameter of 50 nm have a cube-cube orientation relationship with the matrix, and these precipitates on {111} planes align along 110 orientation.Since the large dissolved La atom will be a barrier to atom diffusion, it leads to an inhibiting effect on the carbides growing.M6C carbides are influenced by La-S phases.La-S phases formed in the center of M6C seem to be the heterogeneous nucleus of M6C to increase the nucleation ratio.It is also noticed that finer M6C carbides precipitated on the {111} planes of the matrix are around large M6C.The finer M6C carbides are caused by the special absorption effect of La-S phases.
