Punched-Out Dislocation Rosettes in Low-Dislocation-Density Copper

Copper single crystals of extremely low dislocation density have been obtained through a thermal cyclic annealing. Ball indentation in the dislocation-free area of (111) surface produced large dislocation rosettes, each arm extending in the 〈110〉 cystallographic orientations consisted of a row of prismatic dislocation half-loops. Half-loops of a diameter larger than 20 μ were easily produced in regular shape and they seemed much less mobile than independent dislocations under glide shear stress.