Imaging the three orientation variants of the DO22 phase by 3D atom probe microscopy

Three-phase NiAlV alloys were investigated using a three-dimensional atom p robe. Ageing at 800 degreesC gives rise to the precipitation of two ordered phases within the supersaturated FCC solid solution, namely Ni3Al (L1(2) s tructure) and Ni3V (DO22 structure). The DO22 phase has three orientation v ariants which need to be identified in 3DAP images. It is shown that an app ropriate choice of analysis site enables us to image the chemical order wit hin both L1(2) and DO22 ordered phases and to distinguish the three orienta tion variants of the DO22 phase in reconstructed images. The lateral resolu tion of 3DAP in these experimental conditions was estimated through simple considerations to be less than 0.3 nm.