STUDY OF SUPERPLASTICITY IN PB-SN EUTECTIC ALLOY USING IMPRESSION CREEP TECHNIQUE

Impression creep method has been used to study the creep behaviour of Pb-Sn eutectic alloy of two different grain sizes, viz., 3.4 and 7.5 m u m in the temperature range of 30-125 degrees C. The deformation resp onse of the fine grained material conformed to regions II and III of a typical sigmoidal behaviour of a superplastic material. The strain ra te sensitivity index values determined for region II, 0.43-0.55, were also indicative of superplastic behaviour. In coarse grained material, superplastic behaviour was seen only at higher test temperatures. The se showed lower values of strain rate sensitivity index, namely 0.21-0 .45. It is concluded that the impression creep technique is attractive for characterising superplasticity when only a small volume of materi al is available.