High temperature creep behaviour of lead-base particulate composites

Abstract

Lead-base particulate composites, namely Pb-5 vol% Zn, Pb-5 vol% Al2O3 and Pb-2.5 wt% PbO have been prepared using powders of lead (atomized), zinc (atomized) and Al2O3 by a powder metallurgy technique followed by deformation processing. Isothermal creep tests have been performed at 100, 150 and 180° C on the recrystallized composites. Internal stresses in the steady-state region have been measured in a Pb-PbO composite to evaluate rate controlling mechanisms. Threshold stress for steady-state creep is observed in P/M lead and Pb-Al2O3 composites at 100 and 150° C, whereas it is absent in Pb-Zn composites. Two distinct stress exponent regions with different activation energies associated with them, are observed over a shear strain rate range of 10−7 to 10−4 sec−1. In the low stress exponent region, grain boundary sliding appears to be the rate controlling mechanism, whereas climb controlled dislocation creep is the operative mechanism in the other region.