Transformation superplasticity of cast titanium and Ti-6Al-4V

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 38; no. 1; pp. 44 - 53
• Main Authors: QIZHEN LI, CHEN, Edward Y, BICE, Douglas R, DUNAND, David C
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 2007; Springer Nature B.V
• Subjects: Applied sciences; Casting; Chemicals; Cost control; Exact sciences and technology; Grain size; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Standard deviation; Superplasticity; Testing; Titanium alloys; Mechanical properties; Superplasticity; Aluminium alloy; Vanadium alloy; Titanium base alloys
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-006-9020-6

Samples of unalloyed titanium and Ti-6Al-4V with a cast, coarse-grain structure were subjected to simultaneous mechanical loading and thermal cycling about their transformation range to assess their capability for transformation superplasticity. Under uniaxial tensile loading, high elongations to failure (511 pct for titanium, and 265 pct for Ti-6Al-4V) and an average strain-rate sensitivity exponent of unity are observed. Samples previously deformed superplastically to a strain of 100 pct show no significant degradation in room-temperature mechanical properties as compared to the undeformed state. Biaxial dome bulging tests confirm that transformation superplasticity is activated under thermal cycling and faster than creep deformation. The cast, coarse-grained titanium and Ti-6Al-4V have similar transformation-superplasticity characteristics as wrought or powder-metallurgy materials with finer grains. This may enable superplastic forming of titanium objects directly after the casting step, thus bypassing the complicated and costly thermomechanical processing steps needed to achieve fine-grain superplasticity. [PUBLICATION ABSTRACT]