Superplasticity in low-alloy steels

Superplasticity has been investigated in three carbon-manganese steels with small additions of Nb, V, Al and Ti. Superplasticity was observed from 800 to 1000°C at strain rates from 0.002 to 0.01 min^-1. Strain rate sensitivities above 0.7 have been observed; however elongations to fracture are quite low with a maximum value observed of 184 pct. The strain rate sensitivity did not vary with strain although it was very dependent on strain rate and temperature. Cold work prior to hot tensile testing enhanced the superplasticity in the vanadium steel. The premature failure of these steels with large strain rate sensitivities has been attributed to crack nucleation due to the fine particle network from the Nb and V precipitation.