Microstructural Characterization of Martensite with Long Period Stacking Order Structure in Hf–Co–Pd Alloy

Abstract

Microstructural characterization of martensite with long period stacking order (LPSO) structure in a Hf–Co–Pd alloy was investigated by transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). LPSO structure with six stacking sequences; 6O (orthorhombic) (Space group: Immm), were newly discovered. Based on the electron diffraction experiments, the lattice parameters of LPSO phase were estimated to be a = 0.33 nm, b = 0.45 nm and c = 1.53 nm. The formation mechanism of martensite with LPSO structure and the crystallographic orientation relationship between parent B2 phase and 6O martensite are also discussed.

Fig. 5 (a) A HAADF-STEM image taken along the [010]_LPSO direction of an LPSO structure in a Hf–30.0 at% Co–20.0 at% Pd alloy. (b) Image intensity profile taken along the white-line X-Y in (a). (c) Fourier filter-processed HAADF-STEM image of LPSO structures. (d) Schematic illustration of the atomic arrangements in the white-framed areas in (c).