Nonuniform Recrystallisation in a Mechanically Alloyed Nickel Based Superalloy

K. Murakami, K. Mino, H. Harada and H. K. D. H. Bhadeshia


The recrystallization behavior of mechanically alloyed and extruded MA6000 oxide dispersion strengthened (ODS) nickel-base superalloy has been studied as a function of the position of the sample in the extruded bar. It was found that there are profound differences across the cross section of the bar, the edge regions recrystallizing more easily relative to the core. Furthermore, the recrystallized grains tend to be much more anisotropic at the edges. It appears that these differences are caused by inhomogeneous deformation. The oxide particles are more aligned along the extrusion direction at the regions near the surface, presumably because of the more extensive deformation in those regions. This explains the greater anisotropy in the recrystallized grains and the relative case of recrystallization (since the boundary mobility along the extrusion direction is high for aligned particles). Stored energy measurements confirm that the observed effects cannot be explained by differences in the driving force for recrystallization.

METALLURGICAL TRANSACTIONS A, 1993, Vol.24, No.5, pp.1049-1055

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