Quasi-Isothermal Forging of Steel-Encapsulated Ti-6Al-4V Billets

Abstract:

Isothermal forging is a common method for manufacturing titanium alloys, but it involves complex processes and equipment. The oxidation of titanium leads to the formation of an alpha-case, which in turn promotes increased crack formation. To prevent this, inert gas is typically required. However, by encapsulating the titanium billet (Ti-6Al-4V) in a steel casing made of AISI 316L, a quasi-isothermal process can be achieved without the need for inert gas. This method maintains protection against oxidation while simultaneously reducing cooling. The sealing of the capsules is crucial to ensure that the titanium is effectively enclosed and protected from the surrounding gases. In this study, various encapsulation methods are compared, including rotary friction welding, diffusion bonding, and press-fitting a lid with an interference fit. The investigation involves differing contact conditions between the titanium and steel sleeve, as well as steel wall thicknesses of 2 mm and 4 mm. These factors showed no impact on the material flow or microstructure of the formed components. Encapsulation can prevent the formation of an alpha-case. Intermetallics form between the titanium and the steel capsule, depending on the contact conditions. The use of graphite as a separating agent prevents the formation of them.

• Periodical: Materials Science Forum (Volume 1186)
• Pages: 13-24
• DOI: https://doi.org/10.4028/p-c0Lqa2
• Online since: April 2026
• Authors: Jytte Möckelmann*, Julius Peddinghaus, Kai Brunotte, Bernd Arno Behrens
• Keywords: Die Forging, Quasi-Isotherm, Steel, Titanium

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