Stress-strain curves of superplastic alloys

Abstract

Force-elongation and stress-strain curves have been analysed for superplastically deformed alloys tested in uniaxial tension under constant cross-head velocity conditions. By considering instability criteria the curves can be divided into three characteristic stages. In the course of the first two stages the samples are work hardened while during the third stage no work hardening takes place, although 85 to 90% of the total deformation occurs at this stage. However, sometimes at the end of stage III a weak strain hardening appears again due to grain growth. From the analysis of stage III the strain-rate sensitivity can be determined in good agreement with other methods.