Fundamental Investigations of Failure during Superplastic Forming Process

Fine grained superplastic alphbeta Ti-6Al-4V alloy was deformed in the temperature range 750-925 C and at strain rates of 0.00001 to 0.0001s. The results indicate that an increase in the deformation temperature or a decrease in the deformation rate is followed by an increase in the value of strain hardening index SHI. In such a situation, the stress-strain rate relation can no longer be represented by the conventional power law formulation without evaluating the effect of strain. The common assumption that a large value of the apparent strain rate sensitivity parameter is associated with a large amount of superplastic ductility is not tenable under test conditions where strain hardening or strain softening effect is noticeable. Keywords Titanium alloys Mechanical behavior Deformation mechanisms.