On the mechanisms of point-defect absorption by grain and twin boundaries

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Abstract
Low- and high-angle grain boundaries, and twin boundaries in aluminium and copper have been observed during in-situ electron irradiation using a high-voltage electron microscope. Evidence is presented for dislocation mechanisms of point-defect absorption in all three types of interface. In grain boundaries, climb of extrinsic dislocation structures leading to equilibration and final inclusion in the intrinsic structure is observed. Any movement of the intrinsic dislocations in a fully equilibrated array would usually be too small to observe using this technique. In coherent twin boundaries, dislocation loops are formed : these grow, coalesce and annihilate, and then renucleate, unlike matrix loops for which nucleation ends at an early stage of irradiation.