Electron Microscopy Study of the Precipitation Processes in Cu-2 wt%Be Alloy

Precipitation Characteristics of the Metastable γ″ Phase in a Cu-Ni-Be Alloy

“…Ni atoms occupied the position of the body heart, the Be atoms were in the eight vertices, and unit cell structure was, as shown in Figure 7 f, a metastable γ″, γ′ phase with a BCT structure, with a lattice constant: a = b < c. In the Figure 6 a HRTEM diagram, the measurement location d (010) p = 0.259 nm, d (001) p = 0.368 nm, and the inter-planar distance of the γ″ phase (001) crystal plane’s two layers of Be atoms and the α-Cu matrix’s inter-planar distance were consistent. However, in the corresponding FFT reciprocal lattice diagram, (002) p and (002) α diffraction point locations were not coincident, which means that d (001) p < 0.368 nm, and the actual measured value was between 0.27 nm to 0.32 nm, Ken’ichi et al [ 21 ] measured the lattice constant of the γ″ phase of the Cu-Ni-Be alloy to be a = b = 0.253 nm, c = 0.29 nm and Watanabe et al [ 13 ] measured the lattice constant of the γ″ phase of the Cu-Ni-Be alloy to be a = b = 0.24 nm, c = 0.28 nm. Two layers of the structure of the γ″ phase were imaged by TEM, showing that its diffraction intensity was weak and vulnerable to interference by the α-Cu matrix’s diffraction wave, as shown in Figure 5 d. The 1/2 {220} α position did not show obvious γ″ phase diffraction spots, while these appeared in the Figure 6 b FFT reciprocal lattice.…”