Effect of change of the specimen thickness on slippage during high-pressure torsion

Abstract

The results of determination of the slippage effect during the high-pressure torsion (HPT) of commercially pure Cu samples using the method of “joint HPT of halves” are presented. It is shown that during the НРТ of Cu at a pressure of 6 GPa and room temperature at the first stage of deformation (n = 0.25 revolutions) slippage is insignificant. After preliminary HPT for n  = 10, during further torsion for n = 0.25 slippage Λ reaches 85%. However, if at the first stage the Cu sample was subjected to HPT for n = 10 on anvils with a groove depth of 0.6 mm, and then the obtained disc was cut into halves that were subjected to joint HPT with n = 0.25 on anvils with a groove of 0.4 mm, the torsional deformation is close to the expected one, slippage is insig-nificant. Hence, the growth of Λ with n increasing up to 10 can be explained by the decrease in the height h of the specimen, because with increasing n the specimen material flows out from under the anvils (in fact, from the deformation zone) and at n = 10 the specimen height becomes less critical.