Investigation of superplasticity by the impression creep technique

Impression creep tests have been carried out on a Zn--22Al eutectoid alloy in two heat-treatment conditions, as a function of applied stress and at temperatures of approx 25-270 deg C. At small grain sizes ( approx 0.9 mu m) and in the temperature range approx 180-270 deg C, the observed deformation response conforms to Regions I, II, and III typical of superplastic behaviour. Furthermore, strain-rate index values determined for Region II fall in the range 0.44-0.51, consistent with superplasticity. It is concluded that the impression creep technique offers considerable potential for characterization of superplastic alloy systems on small specimen volumes. Graphs. 20 ref.--AA