Low-frequency internal friction of strongly deformed zinc and aluminum

Low-frequency internal friction of zinc (99.95%) deformed by hydrostatic extrusion and drawing to a total reduction of 99.5% and aluminum (99.6%) deformed by hydroextrusion to 99% and partially recrystallized in the processes of deformation, recovery, and annealing. The hydrostatic weighing method was used to measure the macroscopic density and the relative volume of pores in zinc after stepped annealings. The porosity was shown to increase internal friction and cause the appearance of an intermediate relaxation peak in Zn and Al in addition to the grain-boundary relaxation peak and the high-temperature peak due to grain-boundary migration during secondary recrystallization. The mechanisms of the porosity effect on the internal friction and grain-boundary migration are discussed.