الفهرس | Only 14 pages are availabe for public view |
Abstract The present work forms an experimental study of the role of grain boundaries and plastic deformation on the mechanical properties of pure zinc. Internal friction, rigidity modulus were t ak en as tools for the present work. A Ke pendulum was used to determine the internal friction and rigidity modulus of the pure zinc wire samples.The internal friction was measured by the free decay method in the frequency range 0.5 - 2.5 Hz and at temperatures from room temperature to o about 200 C. The effect of straiQ amplitude on the internal friction values within the experimental range was tested and was found to be negligibly small. The internal friction v§ temperature showed a remarkable relaxation peak at about 85 Co. This relaxation peak was associated with a relaxation in the rigidity modulus. The vibration frequency of the pendulum was pre-adjusted in the range 0.5 - 2.5 Hz by a control of the total suspended load. Static stressing the sample changed slightly the internal friction peak shape and shifted its position to higher temperatures. The internal friction peak shape method was used to measure the activation energy for the process in action and was found to be abou to. 8 ev .. T his v a 1 u e was in ago od ~reement with the corresponding experimental value obtained by the peak shift method. The calculated activation energy remained the same indicating no change in the relaxational mechanism by increased loading. The increased line tension of dislocations by stressing due to the applied load, seemed to increase the vibrational frequency of the dislocation segments, which |