The nature of grain-boundary dislocations and local order in boron-doped Ni3AI

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Abstract
The question of whether a disordered f.c.c. phase exists and whether it has a significant effect on the plastic response at grain boundaries in boron-doped nickelrich Ni3Al alloys is addressed. Image matching of simultaneous two-beam electron micrographs is used to identify the nature of the Burgers vectors of both intrinsic and extrinsic grain-boundary dislocations in general large-angle boundaries and σ = 3 boundaries (both incoherent and coherent) in a boron-doped Ni-24 at.% Al alloy. All the determined Burgers vectors were found to be vectors of DSC lattices based on the L12 crystal structure and did not involve DSC vectors that would have been expected if a disordered f.c.c. phase were present in the vicinity of the boundaries.