X-ray Fluorescence Holography for a Ti–Nb Binary Alloy Consisting of the Martensite, Austenite and Omega Phase

The local atomic structure near an Nb atom in a Ti–20 at.%Nb alloy single crystal, which consists of the β, α'' and ω Ti phases, was investigated by means of X-ray fluorescence holography (XFH). The atomic images were reconstructed in the vicinity of an Nb atom, which is one of the typical β stabilizing elements in β Ti alloys. Most atoms in the β Ti primary phase were reconstructed clearly. The atoms in the α'' Ti martensite phase could not be reconstructed, because the α'' Ti martensite has the crystal structure with low symmetry. Some atoms in the ω Ti fine precipitates were reconstructed successfully, although the amount of the ω Ti phase was much smaller than that of the β phase. An Nb atom and its first nearest neighbors tend to keep the BCC structure even upon the ω Ti phase formation