Development of Low Temperature Bonding Technique of Titanium and Zirconium Using Hydrogen Diffusion-Induced Phase Transformation

Abstract:

A new bonding technique of titanium and zirconium conducted at low temperatures was developed utilizing the hydrogen-induced transformation. Hydrogen charge treatment of the faying surfaces of titanium and zirconium was conducted with varying the charging time between 3.6-700ks prior to diffusion bonding. Diffusion bonding of hydrogen-charged titanium and zirconium was carried out at 600-800°C for 0.6-1.8ks applying the bonding pressure of 5-10MPa in vacuum. Titanium and zirconium hydrides were formed at faying surfaces after hydrogen charge treatment. The β-transus temperature at faying surfaces of titanium and zirconium was reduced to approx. 450-550°C with hydrogen-charging. The bond layer was phase transformed to a bcc structure (β) at the bonding temperature due to the hydrogen diffusion during bonding process. Grain growth across the prior bond interface was observed in the joints bonded at 750-800°C after hydrogen-charging for 300-500ks. Tensile strength of titanium joints bonded at 800°C attained approx. 70% of the base metal strength (approx. 1.6 times as high as non-charged joints), and corrosion resistance of the joints was comparable to that of the base metal. Furthermore, tensile strength of zirconium joints bonded at 800°C was approx. 1.7 times as high as non-charged joints. It follows that the solid-state bondability of titanium and zirconium at low temperatures was improved compared to the conventional diffusion bonding (direct bonding without hydrogen-charging).

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 3010-3015
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.3010
• Online since: January 2012
• Authors: Kazuyoshi Saida, Hiroyuki Ogiwara, Kazutoshi Nishimoto
• Keywords: Hydrogen-Induced Transformation, Joint Properties, Low Temperature Diffusion Bonding, Microstructure, Titanium, Zirconium

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