Torsional creep behavior of polycrystalline lead at high temperatures
Michalopoulos, Constantine D
Brotzen, Franz R.
Master of Science
The torsional Creep behavior of polycrystalline lead was studied at temperatures near the melting point, and at low stresses. Secondary creep consisted of two clearly divided portions, with the second portion having a higher creep rate than the first. The strain at which acceleration took place was essentially independent of stress and temperature. The accelerated rate region of constant creep rate extends to very high values of strain. The activation energy for this region was determined to be 24,000 calories per mole as compared to the value of 27,000 for the secondary stage. These facts and additional experimental observations led to the speculation that creep of lead at high temperatures occurs by a dislocation climb mechanism and that grain boundary migration is responsible for the increase in the creep rate.