Strengthening Effect of Decreased Dislocation Density After Annealing in Pure Aluminum or Copper

Plastic deformation in metals occurs through the generation and movement of dislocations, leading to strain hardening. The dislocation density has long been known as a measure of work hardening in metals and alloys, and factors other than dislocation density that increase strength have not been experimentally identified. It is difficult to quantitatively analyze dislocations, and the generation and movement behavior of dislocations differs depending on the metal. In this study, we designed a simple experiment to easily observe the effect of dislocation configuration and reaction with grain boundaries on strength. We found that the regular arrangement of dislocations in pure Al and Cu can increase strength despite the low dislocation density. Therefore, we have discovered a hidden mechanism in work hardening that could be applied to develop new ways of strengthening metallic alloys through thermomechanical treatment. Graphical abstract