Characterizing solute hydrogen and hydrides in pure and alloyed titanium at the atomic scale

Abstract

Ti has a high affinity for hydrogen and are typical hydride formers. Ti-hydride are brittle phases which probably cause premature failure of Ti-alloys. Here, we used atom probe tomography and electron microscopy to investigate the hydrogen distribution in a set of specimens of commercially pure Ti, model and commercial Ti-alloys. Although likely partly introduced during specimen preparation with the focused-ion beam, we show formation of Ti-hydrides along α grain boundaries and α/β phase boundaries in commercial pure Ti and α+β binary model alloys. No hydrides are observed in the α phase in alloys with Al addition or quenched-in Mo supersaturation.

Quantification of solute deuterium in titanium deuteride by atom probe tomography with both laser pulsing and high-voltage pulsing: influence of the surface electric field

“…Previous studies have shown that the measured H composition in titanium hydride by APT with HV pulsing was 10 at%-15 at% less than the value expected from the stoichiometry given by the bulk phase diagram [5,13]. In an attempt to optimize the experimental parameters to obtain an average composition close to the stoichiometry of the compound, we conducted series of measurements with HV pulsing by varying experimental parameters, such as pulse frequency, base temperature, pulse fraction, etc, while other parameters were kept constant.…”

“…It has been reported that H could be easily introduced into Ti materials during conventional focused ion beam (FIB) milling conducted at room temperature [5,28]. The possible sources of H inside the SEM/FIB could be the decomposition reactions of the hydrocarbon and moisture from the vacuum chamber, or of the organometallic precursor for Pt-chemical vapor deposition, stimulated by the energetic electron/ion beam.…”

“…However, the quantitativeness of H measurement by APT is yet to be established. Previous studies [5,13] have shown that the measured hydrogen composition of hydrides, titanium hydride and zirconium hydride, differs from stoichiometry. This is a known issue in the APT analysis of many materials including carbides [14,15], oxides [16][17][18][19], and nitrides [20,21].…”

“…Ni, Al, Ti, Zr, Mg-based alloys. H either in solution, trapped at crystal defects [1,2] or in the form of hydrides [3][4][5], has a distinct influence on mechanical properties of metals, such as ductility, strength, or toughness. Many mechanisms for hydrogen embrittlement such as HELP (Hydrogen-enhanced local plasticity), HEDE (Hydrogen-enhanced decohesion), AIDE (adsorption-induced dislocation-emission), HEVE (Hydrogen-enhanced vacancy embrittlement), hydride-induced cracking, etc, have been proposed [6].…”

“…APT is the only technique which can visualize the 3D distribution of the H at the sub-nanometer scale, in particular at microstructural features, e.g. precipitates [1,2] or grain boundaries [5,12]. However, the quantitativeness of H measurement by APT is yet to be established.…”