Superplastic deformation of Ti-55 alloy sheet

The superplastic tensile tests were performed at various temperatures(890-910℃) and initial strain rates (4.4×10~(-4)-1.76×10~(-3) s~(-1)).The results show that the fine-grained Ti-55 sheet,with an average grain size about 4μm, exhibits excellent superplasticity.On the optimal superplastic condition of 900℃and initial strain rate 8.8×10~(-4) s~(-1),a maximum elongation of 1 300%can be achieved.There exists an optimal strain rate of 8.8×10~(-4) s~(_1) for each test temperature to get the highest strain,and the superplastic elongation would be significantly reduced at strain rates higher or lower than the optimum strain rate.The temperature for the best superplasticity of Ti-55 sheet moves to higher temperatures at high strain rates.The influence of the deformation on microstructure is obviously.The strain induce grain growth is one of the most prominent characteristic during superplastic deformation.