In-situ scanning electron microscope thermal desorption spectroscopy (SEM-TDS) analysis of thermally-induced titanium hydride decomposition and reformation

Hydrogen embrittlement (HE) micro-mechanisms are intrinsically challenging to investigate even for metallic materials with simple microstructures, due to the spatial and temporal scales involved. This underlying complexity is increased, when hydrogen uptake induces microstructural changes, which precede the apparent embrittlement. Unraveling these micro-mechanisms calls for integrated characterization approaches that can provide spatially- and temporally-resolved insights regarding hydrogen effects. For this purpose, we present an integrated scanning electron microscopy - thermal desorption spectroscopy (SEM-TDS) technique here, which is employed to carry out an in situ study of hydrogen induced effects in Ti-6Al-4 V. Focusing on the interplay among the neighboring α and β phases in this material enables a deeper understanding of the effects of cyclic heat treatments: When this hydride forming alloy is heated, the dissociated hydrogen from the hydride diffuses into the neighboring α-Ti grains. Upon cooling, the hydrogen content in the α-Ti is supersaturated, which leads to the formation of a new hydride phase and an increase in the defect density in the grain. These insights provided by the SEM-TDS technique can be used to guide HE resistant microstructure design efforts, as well.