Titanium-alloy systems are advanced functional and structural materials used extensively in various industrial domains including aviation, marine, biomedical, nuclear, and automotive sector. Their outstanding utilization can be attributed to their high strength to weight ratio, good creep behavior and corrosion resistance [1]. Further, titanium exhibits a strong inclination to hydrogen. When these alloys are exposed to hydrogen atmospheres such as fuel or a fuel part, this inclination leads to a change of the material properties, particularly fracture toughness and ductility. In addition, the behavior of hydrogen in various titanium-alloy systems, mainly in terms of solubility and diffusion kinetics, exhibits significant variations, leading to distinct hydrogen interaction mechanisms. It is to highlight that the diffusion behavior of hydrogen mainly depends upon microstructural features such as grain boundaries, vacancies and dislocations, the existence of several phases and their phase boundaries, internal porosities and alloying elements [2]. Hence, an in-depth knowledge of the microstructural formation and their kinetics during the processing routes of titanium alloys is necessary to understand the fundamental mechanisms of hydrogen diffusion.

The aim of this work is to understand the influence of microstructural features produced via different production routines such as Additive Manufacturing (AM) and Field Assisted Sintered Technologies (FAST) methods on the hydrogen diffusion behavior in titanium-alloy systems. Therefore, a development plan was drawn for processing different titanium alloys to obtain diverse microstructures and phase compositions. Microstructure and material properties were analyzed and evaluated. In addition, the initial hydrogen permeation tests were conducted on the as-built samples to understand the rate of the diffusion. Glow-discharge optical emission spectroscopy analysis was performed to assess the depth profiles of hydrogen intensity in the surface layer area of the material. The obtained as-built microstructure of different FAST sintered titanium-alloy systems is depicted in the Figure 1. Through a comprehensive analysis, this work leads to a better understanding and monitoring of the influence of different manufacturing routines, heat treatment conditions, alloy compositions and microstructural configurations on the diffusibility of hydrogen.