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

Morphology, orientation and diffraction patterns of δ-Ni2Si precipitates in a Cu–Ni–Si alloy are investigated by TEM and HREM. Many disk-shaped nanosized δ-Ni2Si precipitates are uniformly distributed in Cu–1.5 wt%Ni–0.34 wt%Si alloy in an over-aging condition. The δ-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 δ-Ni2Si precipitates with Cu-matrix can be determined as (1 0 0)p||{0 0 1}Cu, [1 0 0]p||〈1 1 0〉Cu and [0 1 0]p||〈1 1 0〉Cu. Two typical diffraction pattern models under [0 0 1]Cu and [1 1 1]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.

► Crystal structure and lattice parameter of δ-Ni2Si embedded in Cu are confirmed. ► The orientation relationships of six variants of δ-Ni2Si with Cu are determined. ► Two diffraction pattern models are simulated which match the experimental results.