The dynamic internal friction (DIF) during the superplastic deformation of a Pb-62 wt% Sn eutectic alloy with an average grain size of 6 mu m has been measured at strain rates of 10(-6)-10(-4) s(-1). An expression for the DIF is derived and used to obtain the activation volume V-a at different strain rates. It is found that V-a stays almost constant with strain for a given test condition except at the beginning of deformation. V-a decreases with increase in strain rate or applied stress. The magnitude of the activation volume is of the order of 10(-27) m(3), which implies that the elementary process of superplastic deformation is possibly associated with the motion of grain-boundary steps or jogged dislocations along grain boundaries. The present work indicates that the DIF technique is a useful tool for detecting the microscopic process of superplastic deformation. [References: 17]
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