DISLOCATION CELL STRUCTURES IN COPPER IN TORSION AND TENSION

A comparative study of the deformation of commercial copper in torsion and in tension was undertaken. Specimens for both tests had the same grain size and underwent the same heat treatment. In tensile specimens , dislocation cell structures were observed in specimens cut in the di rection of the applied load while specimens were obtained parallel to the longitudinal axis in torsion. This was followed by transmission el ectron microscopy examination. It was observed that in tension, the wo rk hardening rate is much higher than in torsion. The dislocation stru ctures in tension are characterized by the formation of sharp subgrain boundaries while in torsion, laminar dislocation structures consistin g of paired sheets evolved together with other paired sheets forming c heckerboard patterns. These patterns were exhibited up to strains of a bout 440%. The resistance to bowing out of free dislocation segments i n the two cases explains the difference in the work hardening for both tension and torsion.