Superplastic behavior of an Al-4wt.T% Ti alloy processed by the powder metallurgy route

The superplastic behavior of an Al-4wt.% Ti alloy processed using rapid solidification powder metallurgy was investigated. The peak value of the strain rate sensitivity index increased with temperature and grain size. The drop in flow stress with increasing grain size and anomalously high activation energy for flow at low strain rates are explained in terms of a grain size and temperature dependent threshold stress for superplastic flow. The origin of the threshold process is interpreted to be the inhibition of grain boundary migration by the particles during superplastic flow. An increase in the activation energy for flow was observed at temperatures close to the melting point of aluminum.