In the seventies some scientific workers from France and Italy suggested that the grain boundary internal friction peak (named the K (e) over cap peak in the literature) widely accepted as a grain boundary process, is...In the seventies some scientific workers from France and Italy suggested that the grain boundary internal friction peak (named the K (e) over cap peak in the literature) widely accepted as a grain boundary process, is originated from the motion of lattice dislocations. Since this problem is one of fundamental importance, this controversy has drawn much international attention. Started from 1982, the Hefei research group made a critical analysis of the large amount of literature concerning this problem and,performed a series of crucial experiments to clarify the controversy. It is concluded that the irrelevant evidence suggested by the controverters comes from the farfetched interpretation and the mis-identification of the internal friction peaks appeared under various experimental conditions and different states of the specimens.展开更多
Internal friction and modulus measurements of nano ZrO<sub>2</sub> solids for different particle sizes （including original compacted and annealed samples） were systematically carried out from room temper...Internal friction and modulus measurements of nano ZrO<sub>2</sub> solids for different particle sizes （including original compacted and annealed samples） were systematically carried out from room temperature to -200℃. It was found that the three peaks （P<sub>1</sub>, P<sub>2</sub> and P<sub>3</sub> corresponding to ascending measurement, or P<sub>1</sub><sup>’</sup>, P<sub>2</sub><sup>’</sup> and P<sub>3</sub><sup>’</sup> corresponding to descending measurement） appeared. By investigating the behavior of internal friction peaks （P<sub>1</sub>, P<sub>2</sub>, P<sub>3</sub> orP<sub>1</sub><sup>’</sup> P<sub>2</sub><sup>’</sup>, P<sub>3</sub><sup>’</sup>）, it is indicated that the origin of peak P<sub>3</sub> or P<sub>3</sub><sup>’</sup> can be attributed to grain boundary relaxation, that is, it is caused by slip of the grain boundaries in nano ZrO<sub>2</sub> solids. The peak P<sub>2</sub> （or P<sub>2</sub><sup>’</sup>）and P<sub>1</sub> （or P<sub>1</sub><sup>’</sup>） may possibly be associated with phase transformation of nano ZrO<sub>2</sub> solids at low temperature range. The energy dispersion decreases and the modulus increases notably with the increase in annealing temperature of the nano samples.展开更多
The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f...The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f -tan φ curves） is also obtained by the interpolation method. An internal friction peak is observed in both the T - tan φ curves and the f - tan φ curves. The activation energy of the peak in the f - tan φ curves is found to be 2.08 ± 0.02 eV and compared to the value of 1.60 ± 0.04 eV in the T - tan φ curves. It is suggested that the change of relaxation strength with temperature should be considered when one calculates the activation energy of the peak in T- tan φ curves.展开更多
文摘In the seventies some scientific workers from France and Italy suggested that the grain boundary internal friction peak (named the K (e) over cap peak in the literature) widely accepted as a grain boundary process, is originated from the motion of lattice dislocations. Since this problem is one of fundamental importance, this controversy has drawn much international attention. Started from 1982, the Hefei research group made a critical analysis of the large amount of literature concerning this problem and,performed a series of crucial experiments to clarify the controversy. It is concluded that the irrelevant evidence suggested by the controverters comes from the farfetched interpretation and the mis-identification of the internal friction peaks appeared under various experimental conditions and different states of the specimens.
基金Project supported by Laboratory of Internal Friction and Defects in Solids, Academia Sinica
文摘Internal friction and modulus measurements of nano ZrO<sub>2</sub> solids for different particle sizes （including original compacted and annealed samples） were systematically carried out from room temperature to -200℃. It was found that the three peaks （P<sub>1</sub>, P<sub>2</sub> and P<sub>3</sub> corresponding to ascending measurement, or P<sub>1</sub><sup>’</sup>, P<sub>2</sub><sup>’</sup> and P<sub>3</sub><sup>’</sup> corresponding to descending measurement） appeared. By investigating the behavior of internal friction peaks （P<sub>1</sub>, P<sub>2</sub>, P<sub>3</sub> orP<sub>1</sub><sup>’</sup> P<sub>2</sub><sup>’</sup>, P<sub>3</sub><sup>’</sup>）, it is indicated that the origin of peak P<sub>3</sub> or P<sub>3</sub><sup>’</sup> can be attributed to grain boundary relaxation, that is, it is caused by slip of the grain boundaries in nano ZrO<sub>2</sub> solids. The peak P<sub>2</sub> （or P<sub>2</sub><sup>’</sup>）and P<sub>1</sub> （or P<sub>1</sub><sup>’</sup>） may possibly be associated with phase transformation of nano ZrO<sub>2</sub> solids at low temperature range. The energy dispersion decreases and the modulus increases notably with the increase in annealing temperature of the nano samples.
基金Supported by the National Natural Science Foundation of China Grant Nos 10171067 and 10374089, and the Foundation of the Institute of Solid State Physics, Chinese Academy of Sciences.
文摘The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f -tan φ curves） is also obtained by the interpolation method. An internal friction peak is observed in both the T - tan φ curves and the f - tan φ curves. The activation energy of the peak in the f - tan φ curves is found to be 2.08 ± 0.02 eV and compared to the value of 1.60 ± 0.04 eV in the T - tan φ curves. It is suggested that the change of relaxation strength with temperature should be considered when one calculates the activation energy of the peak in T- tan φ curves.
