Accelerated formation of an ultrafine-grained structure in a two-phase Ti alloy during compression with decreasing temperatures

ABSTRACT

Ultrafine-grained (UFG) structure is beneficial for overcoming the strength-ductility trade-off and enhancing the superplasticity of two-phase Ti alloys. Recently, it has been demonstrated that compression with decreasing temperatures is effective for producing UFG two-phase Ti alloys initially with lamellar microstructures. However, the effect of lamellar thickness on the microstructural evolution during this process has not yet been fully elucidated. In this study, Ti-6Al-4V alloys with different lamellar thicknesses were compressed while the processing temperature was decreased from 800°C to 600°C. The thinner lamellar microstructure was preferable for preventing void/crack formation, while accelerating the continuous dynamic recrystallisation, thus providing a fully UFG structure at a relatively low strain of 1.4. In addition, the origin of different plastic flows in each sample was analysed in detail by analysing the microstructural evolution. These findings demonstrate that the processing method is effective for reducing the grain size of a two-phase Ti alloy without severe plastic deformation techniques, which require large strain (≥4). A reduction in the strain required to achieve the UFG structure would be beneficial because conventional metal-forming processes, i.e. rolling, extrusion, or forging, which are suitable for mass production, could be used.

KEYWORDS:

• Titanium
• compressive testing
• submicrocrystalline alloys
• microstructure
• plastic deformation

Acknowledgments

This study was supported by the Civil-Military Technology Cooperation Program of the Ministry of Trade, Industry, and Energy [grant number 16-CM-MA-10]; and the Fundamental Research Program of Korea Institute of Materials Science, Republic of Korea [grant number PNK6230].

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Korea Institute of Materials Science [grant number PNK6230]; Ministry of Trade, Industry and Energy [grant number 16-CM-MA-10].