Hydrogen Behavior in GTA Welded Ti-6Al-4V and Beta-21S Aerospace Applicative Titanium Alloys

Abstract

Ti-6Al-4V and β-21S (Ti-15Mo-3Al-3Nb-0.3Si, wt%) titanium alloys were exposed to a hydrogen-containing environment, introduced by Gas-Tungsten Arc welding via a mixed Ar + 5% H2 shielding gas. The different characteristics of hydrogen absortion/desorption behavior and trapping in the welded Ti-6Al-4V and β-21S alloys were studied by means of thermal desorption spectroscopy (TDS). Thermal spectra analysis is supported by data from a variety of other experimental techniques, e.g., Leco hydrogen determinator and microstructure investigations. In the specimens welded in hydrogen-containing environment, no cracking was observed. However, the complex process of hydrogen desorption was found to be significantly affected by the microstructure developed in the alloys after welding. The unique microstructural morphology, the presence of potential irreversible trapping sites and phase transitions (oxide dissociation) were considered to be the potential parameters affecting the hydrogen desorption behavior from the alloys.