Dislocation-Controlled Low-Temperature Superplastic Deformation of Ti-6Al-4V Alloy

The superplastic tension and deformation mechanism of Ti-6Al-4V alloy at 923 K and a tensile speed of 10 −3 , 5 × 10 −3 , or 5 × 10 −2 s −1 was studied on an AG 250KNE electronic tension tester. Through theoretical modeling, the unit dislocation count of this alloy during superplastic deformation was introduced into the Ruano–Wadsworth–Sherby (R-W-S) deformation mechanism map, and a new deformation mechanism map involving dislocation count was plotted. Thereby, the mechanism underling the low-temperature superplastic deformation of this alloy was predicted. It was found the superplastic tension of Ti-6Al-4V at the tested temperature was controlled by dislocation movement, and with an increase in strain rate, the deformation transited from the dislocation-controlled mechanism with a stress index of 4 to the dislocation glide mechanism with a stress index of 5 or 7. At the strain rate of 10 −3 s −1 , this alloy reached the largest tension rate of 790% and strain rate sensitivity index of 0.52 and had excellent low-temperature superplastic properties.