Study of the high-efficiency superplastic deformation of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si alloy based on the strain rate sensitivity index m

A newly developed superplastic deformation (SPD) method called high-efficiency superplastic tension based on the strain rate sensitivity index m (m-HESPD) is proposed and realized. The so-called maximum strain rate sensitivity index (m) superplastic tension (MaxmSPD) is first used to study the SPD of Ti 6Al 2.5Mo 1.5Cr 0.5Fe 0.3Si. Using (m-HESPD), the SPD of the Ti-alloy is conducted under the strain rate between the upper strain rate, at which the maximum m is obtained, and the lower strain rate, under which the minimum m occurs. The MaxmSPD is realized cyclically with the strain rate in such a way that the excellent superplasticity can be obtained. To ensure the strain rate changing cyclically in the high strain rate zone, the measurement of strain rate is critical. In this research, m is dynamically measured by the velocity change approach using a tailor-made computer control system. In the strain rate decreasing process, if the SPD is still realized in the high strain rate zone and the further decrease of deformation velocity is possible.