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

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.