Flow behavior and microstructure in Ti-6Al-4V alloy with an ultrafine-grained alpha-single phase microstructure during low-temperature-high-strain-rate superplasticity

Hiroaki Matsumoto , Vincent Velay (1) , Akihiko Chiba (2)

1 ICA - Institut Clément Ader
2 Institute for Materials Research, Tohoku University

Grain refinement of Ti-6Al-4V alloy (hereafter designated as Ti-64 alloy) is well recognized as a method for revealing the superplasticity at lower temperature or higher strain rates. This work examines the superplastic flow behavior of the ultrafine-grained (UFG) Ti-64 alloy (d(alpha) = 0.4 mu m) consisting of single a phase in relation to microstructural evolution during deformation at 700 degrees C. Detailed microstructural evaluation reveals that the superplastic deformation mode of grain boundary sliding (tested at 700 degrees C-10(-2) s(-1)) can be reasonably explained in relation to the Ball-Hutchison model at initial stage of deformation and the Gifkins Core-Mantle model at latter stage of deformation. During superplastic deformation, the beta-precipitation occurs and contributes to accommodation mechanism of stress concentration at grain boundaries. This work also discusses the superplastic flow behavior in comparison with flow behaviors according to the Bird-Mukherjee-Dorn (BMD) generalized constitutive relation and the model which considers the effect of dynamic grain growth during deformation.

Mots clés: Superplasticity; Titanium alloy; Flow-behavior; Grain-boundary-sliding

Domaines: Sciences de l'ingénieur [physics]

Hiroaki Matsumoto, Vincent Velay, Akihiko Chiba. Flow behavior and microstructure in Ti-6Al-4V alloy with an ultrafine-grained alpha-single phase microstructure during low-temperature-high-strain-rate superplasticity. Materials & Design, 2015, 66, p. 611-617. ⟨10.1016/j.matdes.2014.05.045⟩. ⟨hal-01611092⟩