High fugacity hydrogen effects at room temperature in titanium based alloys

摘要

Titanium based alloys are ranked among the most important advanced materials for a variety of technological applications, due to their combination of a high strength/weight ratio and good corrosion behavior. However, in many of these technological applications, this alloy is exposed to environments which can act as sources of hydrogen, and severe problems may arise based on its susceptibility to hydrogen embrittlement. Both the severity and the extent of the hydrogen interaction with titanium based alloys are directly related to the temperature. Therefore, a comprehensive knowledge of hydrogen effects at room temperature in titanium based alloys will assist in determining the reliable use of these alloys in direct contact with ambient-temperature hydrogen-containing environments. The objective of this paper is to better understand the combined role of microstructure and room-temperature high fugacity hydrogen on titanium based alloys. The paper deals in detail on the effect of hydrogen at room temperature in the Ti-6A1-4V alloy, thermo-mechanically treated to a duplex and a fully lamellar microstructure. Hydrogen effects on the microstructure are studied using X-ray diffraction and electron microscopy, while the absorption and desorption characteristics are determined, respectively, by means of a hydrogen determinator and thermal desorption spectroscopy. Preliminary results at room temperature revealed hydrogen-induced straining and expansion of the lattice parameters in both alloys, at low-to-moderated hydrogen concentrations. With the increase in hydrogen content, in both duplex and fully lamellar Ti-6A1-4V alloy, cracking and second phases formation (hydrides) were observed. The main characteristics of hydrogen absorption/desorption behavior, as well as hydrogen-induced microstructural changes in both microstructures are discussed in detail.