Structure-property correlation in nickel modified Ti-6Al-4V alloy - a study in superplasticity
Superplastic deformation (SPD) properties of (..cap alpha.. + ..beta..) Ti-6Al-4V modified by the addition of 2% Ni (Ti-6Al-4V-2Ni) were investigated in the temperature range 750 to 870/sup 0/C and with strain rates form 5.0 x 10/sup -5/ to 5.0 x 10/sup -3/ s/sup -1/. Emphasis of the study was direct toward considering the contribution of the two-phase nature of the Ni-modified Ti alloy and the microstructural evolution during SPD to the theory of micrograin superplasticity. It was found that the main structural changes taking place were those of deformation-enhanced phase size and in-situ recrystallization, inducing phase refinement of both ..cap alpha.. and ..beta... The corresponding effects on the superplastic flow were strain hardening and strain softening, respectively. The maximum attainable superplastic ductility was associated with a dynamic balance between strain hardening and strain softening as well as with an increase in the interconnectivity of the softer phase ..beta... It was also determined that, as a consequence of microstructural evolution, the phenomenological parameters m, p, and Q were not constant in the temperature and strain rate range tested. Furthermore, optimum superplasticity (expressed in terms of ductility to fracture) was found to be a complex function of temperature phase proportion and phase-size evolution.
- Research Organization:
- California Univ., Davis (USA)
- OSTI ID:
- 5285779
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
CRYSTAL STRUCTURE
DUCTILITY
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ADDITIONS
NICKEL ALLOYS
PHASE STUDIES
PLASTICITY
TENSILE PROPERTIES
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
VANADIUM ALLOYS
VERY HIGH TEMPERATURE