Effect ofβ volume fraction on the dynamic grain growth during superplastic deformation of Ti3Al-based alloys
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The superplastic deformation behavior of Ti3Al based(α 2+β alloy was studied with respect to the volume fraction of α2/β. Three alloys containing 21, 50 and 77% in volume fractions ofβ exhibited large tensile elongations of over 500% at 970°C with a strain rate of 2.5x10-4 sec-1. The largest elongation was observed in the alloy with 21% ofβ. As the volume fraction ofβ phase increased, the flow stress and correspondingly, the strain-rate sensitivity values decreased. Due to the higher diffusivity of Ti in,β phase than in α2 phase, the increase inβ volume fraction from 21 % to 77% accelerated the dynamic grain growth, and degraded the superplasticity of the Ti3Al-based alloys. The strain-based grain growth behavior was quantitatively analyzed and incorporated into a constitutive equation. The calculated flow curves are in agreement with the experimental ones in the stable deformation region.
Key wordsdynamic grain growth superplasticity Ti3Al β volume fraction
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