Constant stress creep and constant true strain-rate tensile tests of the superplastic alloy PbSn

Strain-time curves and stress-strain curves have been obtained for the superplastically deformed PbSn eutectic tested in creep under constant stress and in tension under true strain-rate conditions at temperatures ranging between –44 and 30° C. It is shown that the flow stress does not depend on strain and time and is only a function of the true strain rate, of the temperature and of the initial grain size. The result is that this superplastic alloy does not strain-harden and that the grain size is constant. The apparent activation energy does not depend on stress and temperature and is equal to 11.5±0.5 kcal/mole.