Orientation and diffraction patterns of δ-Ni2Si precipitates in Cu-Ni-Si alloy

Morphology, orientation and diffraction patterns of delta-Ni2Si precipitates in a Cu-Ni-Si alloy are investigated by TEM and HREM. Many disk-shaped nanosized delta-Ni2Si precipitates are uniformly distributed in Cu-1.5 wt% Ni-0.34 wt% Si alloy in an over-aging condition. The delta-Ni2Si precipitates preserve an orthogonal structure with a = 0.708 +/- 0.005 nm, b = 0.504 +/- 0.005 nm, and c = 0.364 +/- 0.005 nm. The orientation relationships of six variants of delta-Ni2Si precipitates with Cu-matrix can be determined as (100)p parallel to{001}Cu, [100]p parallel to < 110 > Cu and [010]p parallel to < 110 > Cu. Two typical diffraction pattern models under [001](Cu) and [111](Cu) zone axis are simulated according to diffraction effects of multiple variants, secondary diffraction and the size of particles, which coincide with the experimental results perfectly. (C) 2013 Elsevier B.V. All rights reserved.