| In order to investigate the cyclic creep acceleration phenomenon, pure aluminium specimens are crept under static and cyclic stress of 54 ㎫ at 308 K. Macroscopically, cyclic creep has faster creep deformation rate and lower creep activation energy than those of static creep. Dislocation structures developed in these specimens are investigated under TEM and some differences are observed. Cell sizes are similar in both cases but thinner cell boundary width, lower tangled boundary fraction, smaller mobile dislocation density and more simple configuration of mobile dislocation are observed in cyclically crept specimen. These results of investigation (faster creep rate, lower activation energy and more recovered dislocation structures under cyclic stress) are interpreated with the roll of excess vacancies which are created by the nonconservative motion of jogged dislocation under cyclic stress. |
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