Observation of Hydrogen Trapping in Fe-0.15 Wt% Ti Alloy by High Resolution Autoradiography

The technique of microautoradiography at the electron microscope scale is used to describe the local repartition of hydrogen introduced by cathodic charging in an Fe-Ti alloy (0.15 Wt% Ti). The role of previous heat treatments of the alloy is studied. Different kinds of trapping sites for hydrogen are observed, mainly decorated dislocations, grain boundaries and interfaces between TiC precipitates and the matrix. A qualitative measurement of the quantity of trapped hydrogen and of the degassing rate leads to a classification of the traps with respect to their interaction energy with hydrogen. The consequence of carbon-hydrogen interactions on the further cracking sensitivity of the alloy, as influenced by the thermal history and carbide repartition, is discussed.