Effect of Heat Treatment and Hydrogen Solution on the Elastic Prop-erties of Titanium

Abstract:
The β-Ti, which is a thermodynamically stable phase at elevated temperatures, is known to have better hydrogen absorption properties than its α phase (α-Ti), which is a stable phase at low temperatures including room temperature. Thus, Titanium is one of the candidates for the fusion reactor design of fusion power generation, which is attracting attention as a next-generation energy source, from the viewpoint of fuel recovery using hydrogen and its isotope storage materials from tungsten, which constitutes the divertor part. Hydrogen solution in some metal is known to play a large roll on the elastic vibration properties. However, past reports on its effect on the elastic properties of titanium applied in a hydrogen environment are limited for both the β-Ti and α-Ti phases, although it is known to be highly sensitive to the presence of hydrogen. Understanding the elastic properties in such environment condition is extremely important for the safety design of the reactor, taking into account the prevention of fracture phenomena due to resonance during earthquakes. On the Other hand, under non-hydrogen environment, the β-Ti alloys have been reported to exhibit low elasticity com-pared to α-Ti Therefore, β-Ti alloys has attracting attention as an implant material for biological tissues, a low elasticity alloy as close as possible to the Young's modulus of human bone is required. For this purpose, control of the texture of β-Ti alloys has been performed by applying the crystal orientation dependence of Young's modulus. Although Titanium is a material of interest in numerous fields and is often exposed to hydrogen environments, limited knowledge is available on the effects of its hydrogen solubility on its mechanical and vibrational properties. We focused on the mechanical properties of pure β-Ti and α-Ti in a hydrogen environment. Especially when restricted to room temperature environments, the solid solution limit of hydrogen in titanium is extremely limited, and more information on mechanical properties below the hydride formation regime needs to be investigated in detail. In this study, we focused on the mechanical properties of pure Titanium and its change due to hydrogen absorption at room temperature, applying vibration reed method with electrochemical hydrogen loading technique. Results show that hydrogen absorption of about 10-3 H/Ti reduced the Young's modulus by 10%. This is a significant change corresponding to an increase in temperature conditions of about 400 K.