The influence of prestrain on ductility in the superplastic Pb-Sn eutectic alloy

Abstract

Experiments were conducted to investigate the effect of prestraining on the ductility of the superplastic Pb-62 wt % Sn eutectic alloy at room temperature. It is shown that prestraining at a fast strain rate in region III leads to a decrease in the elongation to failure on subsequent testing at a slower rate in region II. This decrease is due to the development of strain inhomogeneities during the prestrain. There is a further decrease in elongation if a holding time is inserted between the prestrain in region III and the subsequent testing in region II. It is shown also that prestraining at a slow strain rate leads to a sharp increase in the elongation to failure on subsequent testing at a fast strain rate. The reasons for these trends are discussed with reference to the occurrence of grain growth and the uniformity of strain.