Identifying titanium hydride in a titanium alloy using EBSD and quantitative backscatter imaging

Instruments used

EDAX^® Velocity™ Ultra, EDAX OIM Analysis™, Cipher^®, and EDAX OIM Matrix™

Background

Identifying hydrogen and hydride phases can be difficult with conventional microanalysis tools. Due to its atomic structure, hydrogen will not emit characteristic x-rays when exposed to either electrons or x-rays. Therefore, it cannot be detected with energy dispersive spectroscopy (EDS) or wavelength dispersive spectroscopy (WDS). Electron backscatter diffraction (EBSD) can determine the crystal structure of a potential hydride phase but cannot verify the presence of hydrogen or rule out other phases with similar crystal structures. In titanium alloys, hydrogen and hydride phases can lead to issues involving hydrogen embrittlement and hydride-induced cracking. Because of this, it is important to be able to confidently identify the presence and position of hydrogen and hydrides within the titanium alloy microstructure. To address this challenge, we have developed the Cipher system, which uses quantitative backscatter electron (qBSE) imaging to determine the presence of hydrogen using a composition by difference method. These results are substantiated using EBSD results.